Operative Strategies



Fig. 13.1
Exposure with Vascular Omni-Flex System (Omni-Tract Surgical; St.Paul, MN) retractor for aortic exposure



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Fig. 13.2
Division of crural fibers transversely allows identification of the anterior surface of the supraceliac aorta


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Fig. 13.3
Adequate aortic exposure requires appropriate use of retractors, and aortic clamp positions


For the more experienced surgeon, assessment of the location of the retroperitoneal hematoma may also help guide operative exposure and proximal control. Often these patients will present with a CT scan that can provide valuable information regarding the site of rupture and anatomy. While supraceliac control is an important surgical maneuver, identification of the involvement of the retroperitoneal hematoma may clue the surgeon to the possibility of obtaining proximal control below the renal arteries. When the retroperitoneal hematoma has not obscured or distorted the duodenum, the retroperitoneum may be incised and rapid control of the infrarenal neck obtained through manual palpation, oftentimes through the superior aspect of the hematoma [14]. The hematoma, often, will dissect the surrounding tissue away from the neck and control can be obtained. The key points with this technique is to be cautious with the inferior mesenteric vein and left renal vein. Iatrogenic injury of the left renal vein, in particular, can lead to additional hemorrhage. While it is a more advanced technique, direct infrarenal aortic clamping with a supraceliac aortic occlusion balloon in place to provide a secondary means of proximal control is becoming a more modern practice.



Distal Control


The location of the distal clamp is largely determined by the extent of the aneurysm, and, oftentimes, much of the retroperitoneal dissection has been done by the periaortic hematoma. In this scenario, the clamps are placed over the identified common iliac arteries. If the patient is stable after proximal clamping or has common iliac aneurysms, minimal dissection of the retroperitoneal aorta is performed by getting control of the bilateral external iliac arteries, followed by the internal iliac arteries. The clamps may then be moved to a more proximal location once the extent of repair is better defined. In order to obtain control of the right external iliac artery, the cecum and terminal ileum and retroperitoneal attachments are divided along the white line (the fusion plane between the peritoneum and retroperitoneum), which is a relatively safe dissection plane. The external iliac artery is usually easily controlled circumferentially, and if the internal iliac artery proves difficult for circumferential dissection, direct clamping using a hypogastric clamp is typically feasible. For identification and control of the left iliac arteries, the sigmoid colon is retracted medially and the white line divided. Once the external iliac artery is identified, similar maneuvers are performed to circumferentially isolate it and dissect the internal iliac artery to the extent necessary to place a clamp. When more expeditious distal control is required, the iliac arteries can be controlled by balloon occlusion after opening the aortic sac to visualize the bifurcation [14].

In instances that require inflation of an aortic occlusion balloon, once proximal clamp control is obtained, the balloon may be removed and the sheath withdrawn into the external iliac artery and a smaller balloon placed to control the iliac artery. With this maneuver, the contralateral iliac artery is the remaining vessel that requires control, which can be obtained with the maneuvers listed previously. This particular sequence may provide benefit in most circumstances as it minimizes the need to reposition the retractors during definitive repair. One particular situation deserves special attention, which is in circumstances when clamping or occlusion of the supraceliac aorta is necessary in an unstable patient. In this situation, the added time for the iliac artery dissection will lead to prolonged bowel and liver ischemia time that will certainly worsen the acidosis and coagulopathy. It is beneficial to be able to move the proximal clamp to either the infrarenal or suprarenal position to allow for visceral perfusion. Since this will require opening the retroperitoneal hematoma, the surgeon should be prepared to obtain balloon control of the iliac arteries from inside the aneurysm should distal clamping prove to be difficult.


Aortic Exposure Near the Aneurysm


When exposing the infrarenal aorta from a transabdominal approach, most aneurysms may be repaired from an infracolic approach. To perform this approach, the transverse colon is retracted superiorly, between moist laparotomy pads to expose the root of the mesentery. The small bowel is gathered to the patient’s right and controlled with either moist laparotomy pads or wrapped in a moist towel. The duodenum is mobilized away from the aorta with careful attention paid to avoid injury to the inferior mesenteric vein. The duodenum should be sufficiently dissected away from the aorta so that a large slotted or fence-type retractor may be easily placed for rightward displacement of the small bowel. To aid in bowel retraction, duodenal and retroperitoneal mobilization should be performed prior to applying static retraction. For cases of rupture, this process is largely facilitated by the dissection performed by the periaortic hematoma. Once this process is complete, the next task is to identify the left renal vein. One of the key preoperative tasks when a CT scan is obtained is to determine the anatomic relationships of the mesenteric vessels, renal arteries, and especially the left renal vein (3.2 % will be retroaortic, 1.6 % circumaortic, 0.2 % with a left-sided IVC, 0.4 % with a duplicated IVC, and 0.4 % with a horseshoe kidney) [15]. Figure 13.4 lists important anatomic factors for open repair when looking at the preoperative CT scan. Once the left renal vein is identified, it should be mobilized. Depending on the location of the aneurysm, the vein is commonly spared, and there are four tributaries that are commonly ligated in an elective setting to minimize injury to the vein as it is retracted (left inferior phrenic vein, left suprarenal vein, left gonadal vein, left second lumbar vein). In the setting of a ruptured AAA, the left gonadal vein and lumbar vein are generally all that is required for cephalad retraction of the left renal vein. The next step is identification of the renal arteries. Another key preoperative task when CT scanning is available is to understand the relationship of the renal arteries to one another and in relationship to the aneurysm. The renal arteries should be identified to avoid clamp injury and the relationship to the aortic neck analyzed. Unfortunately, due to the expanded use, improved technology, and operator proficiency, most open repairs for rupture are done when there is an inadequate infrarenal aortic neck. When this is encountered, the aorta above the renal arteries should be dissected with care taken to identify the superior mesenteric artery, particularly as the dissection proceeds cephalad. If necessary for proximal exposure, the left renal vein may be ligated with the preferred technique to perform the ligation close to the inferior vena cava and no ligation of the left renal vein tributaries to allow for collateral drainage. The left renal vein can also be divided between two vascular clamps for additional exposure and repaired at the conclusion of the case. Other important preoperative tasks are to identify whether there is one or multiple renal arteries and their origin since they have segmental embryologic development, giving rise to frequent anomalous origins or accessory renal arteries.

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Fig. 13.4
Important anatomic relationships when analyzing a preoperative CT scan for open repair


Aneurysm Repair


Once proximal aortic control (either clamping or balloon occlusion) is achieved, the aortic neck has been established, and distal control has been obtained, consideration should quickly be made for possible repositioning of proximal aortic control to a desired location preferably below the renal arteries but if needed below the SMA. Either position of the clamp is possible, but there will be more back bleeding from uncontrolled lumbar arteries and collaterals when the clamp is further from the proximal anastomotic site. Once the aneurysm is clamped and ready for repair, the aneurysm is opened along the anterior surface and all thrombus removed from the aneurysm sac. The aneurysm is tailored to the proximal neck and often a self-retaining retractor helps keep the aneurysm sac open. Any large back-bleeding lumbar arteries should be quickly oversewn. A helpful technique in avoiding excessive lumbar back bleeding is to place hemoclips on the lumbar arteries after gaining proximal and distal aortic control and prior to opening the aneurysm sac. The aorta is sized and a tightly woven Dacron or GORE-TEX graft is sutured to the aortic neck and either designed as a tube graft or bifurcated graft. In cases where it is necessary to perform an aortic endarterectomy or the proximal neck is friable, a felt strip is useful in reinforcing the aortic wall suture line. The suture line should be performed with a large needle that allows a deep-seated continuous suture line. Once the proximal anastomosis is completed, the proximal clamp may be moved down to the graft to allow perfusion of the visceral and renal arteries, if required. The distal anastomosis, if sewing a tube graft to the aortic bifurcation, is performed in a similar manner after clamp control of the common iliac arteries is established (by replacement when necessary of the distal balloon control). Should a bifurcated graft be required, suitable anastomotic sites are identified along the iliac arteries, and an end-to-end (common iliac) or end-to-side anastomotic technique (external iliac) is preferred to preserve pelvic circulation unless there is concomitant aneurysmal disease. Care needs to be taken to ensure that the graft is passed under the ureters.

Reimplantation of the inferior mesenteric artery (IMA) was a topic of discussion in the past with ruptured AAAs. In the elective setting if there is adequate back bleeding from the IMA or no bleeding signifying occlusion, it can routinely be ligated. However, if the back bleeding is poor, it should be reimplanted. Numerous studies found that routine reimplantation of the IMA provides no benefit over maintaining adequate organ perfusion in the perioperative setting [16]. Others have advocated selective ligation and reimplantation based on clinical bowel inspection. Unlike in elective aortic reconstruction, detailed knowledge of colonic collateral circulation is difficult to obtain for all patients undergoing a ruptured AAA repair. Our approach is to inspect the IMA and if possible based on the stability of the patient reimplant the IMA.


Removal of Transfemoral or Transbrachial Sheath and Bowel Assessment


Aortic retractors should be left in place at this point, and if an inferior bar on the Omni retractor is used, this should be removed to allow easy access to the femoral sheath, if necessary. The sheath should be left in place and the femoral artery exposed proximally and distally to allow control during the arteriotomy repair. Interrupted sutures are beneficial in minimizing any narrowing of the arteriotomy repair. Similar repair for a transbrachial sheath should also be performed if used. If used, heparinization is reversed at this point to ensure adequate hemostasis of the repair. Once the aneurysm repair is completed, the aneurysm sac is closed along with the retroperitoneum to ensure no exposed graft may touch the small bowel to avoid future aortoenteric fistula. Often, in the setting of a large retroperitoneal hematoma, the retroperitoneum cannot be re-approximated. In this setting, an opening is created in the gastrocolic ligament, and the omentum can be mobilized and passed through this opening to cover the graft so that it is separated from the small bowel. The small bowel is returned to its anatomic position and assessment of bowel viability should be performed. Areas of questionable bowel should be assessed by means of Doppler on the antimesenteric border, fluorescein wood’s lamp with injection of methylene blue, or planned re-exploration.

With the sheath in place if an aortic occlusion balloon was utilized, an arteriogram can easily be performed if there is concern about lower extremity perfusion prior to removing it. If a preclose technique for the percutaneous access was utilized, the sutures can be tied at this point [17]. Otherwise, a femoral incision with femoral artery repair is relatively rapid and easy to perform, and if needed, proximal control from an intra-abdominal approach can be obtained, in the setting of a high puncture of the femoral artery.


Assessment for Intra-abdominal Hypertension and Abdominal Compartment Syndrome


Prior to fascial closure, intra-abdominal hypertension assessment is necessary. Elevated abdominal pressures (above 20 mmHg) are common following repair (50 % of patients) with around 20 % developing the abdominal compartment syndrome and its association with increased mortality [18, 19]. Factors predictive of patients who are at increased likelihood for abdominal compartment syndrome are those who receive unbalanced blood product resuscitation (less than one unit of plasma for every 2 units of red blood cells) or significant early postoperative resuscitation with crystalloids [20, 21]. Though data establishing patients that will need increased postoperative resuscitation requirements are not available, factors associated with increased risk of ischemia-reperfusion insult are preoperative hypotension, 6 or more liters of blood loss, and intraoperative resuscitation with 12 or more liters [22]. A useful intraoperative technical assessment is to obtain a baseline peak airway pressure with the abdomen completely open. Clamps may then be placed on the fascia and the fascia approximated with assessment of any change in peak airway pressure. An airway pressure over 30 mmHg or significant increase should prompt concern for compartment syndrome and the need for delayed abdominal closure. Any clinical concern for abdominal hypertension or the subsequent development of compartment syndrome should prompt delayed fascial closure. Significant acidosis, coagulopathy, and hypothermia should also prompt delayed closure as it is rapid and will facilitate more rapid lethal triad correction by minimizing additional operative time. Temporary abdominal closure is easily obtained using a system designed for open abdominal drainage, such as the ABThera open abdomen negative pressure therapy system for temporary abdominal wall closure (KCI; San Antonio, TX). This and other negative pressure systems are tailored and placed onto the gutters to ensure adequate peritoneal drainage. With the ABThera system, there is a fenestrated visceral protective layer that may be customized to the patient’s body habitus with the goal to have the edges reach well into the paracolic gutters and pelvis so as to optimize peritoneal fluid drainage (Fig. 13.5). Over top of this, placed is a fenestrated piece of foam to approximate the abdominal wall and centralize the drainage process to the canister. This is then sealed with the provided clear drape over the abdominal wall with drape adherence improved by ensuring the skin is dry and using an adhesive skin protective barrier, such as mastisol (Eloquest Healthcare; Ferndale, MI). The drape is then cut with the open abdomen tubing set then placed directly over the clear drape and connected to the 1 L canister and negative pressure therapy unit. The negative pressure unit may provide 100–150 mmHg of negative pressure with 125 mmHg being a common setting. Other methods have been described such as simple coverage of the abdomen with an iodine impregnated drape, but these may not optimize peritoneal drainage. Temporary abdominal closure technique in patients with suspicion of abdominal compartment syndrome is maintained with re-exploration occurring every 24–48 h with closure performed as soon as possible to avoid the loss of abdominal wall domain and the need for complex abdominal wall closure. It is important to note that the patient needs continuous intubation while the abdominal wall is temporarily closed. Early abdominal closure is optimal, though not always possible due to the significant volume resuscitation and substantial bowel edema caused by systemic inflammatory response in the first 24–48 h following ruptured aneurysm repair. Median closure time is 6 days and may often be achieved with primary fascial closure when open abdomen times are short [23].

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Fig. 13.5
Placement of an abdominal wound vac following repair of a ruptured abdominal aortic aneurysm. Demonstrated the technique of temporary abdominal closure is easily obtained using a system designed for open abdominal drainage, such as the ABThera open abdomen negative pressure therapy system for temporary abdominal wall closure (KCI; San Antonio, TX). In the top row there is a there is a fenestrated visceral protective layer that may be customized to the patient’s body habitus with the goal to have the edges reach well into the paracolic gutters and pelvis so as to optimize peritoneal fluid drainage. The middle row demonstrates a piece of foam to approximate the abdominal wall and centralize the drainage process to the canister. Notice that this layer is best secured by using staples to secure the foam to the wound edges. The bottom row demonstrates sealing of the AbThera with the provided clear drape over the abdominal wall. Drape adherence improved by ensuring the skin is dry and using an adhesive skin protective barrier, such as mastisol (Eloquest Healthcare; Ferndale, MI). The drape is then cut with the open abdomen tubing set then placed directly over the clear drape and connected to the 1L canister and negative pressure therapy unit.The negative pressure unit may provide 100-150mmHg of negative pressure with 125mmHg being a common setting


Conclusion


Open repair of abdominal aortic aneurysms has evolved significantly over the past decade, particularly with the increased use of endovascular aortic balloon occlusion and delayed abdominal wall closure. The fundamental tenants of the repair though haven’t changed – avoidance of general anesthetic until prepared for rapid proximal aortic control, rapid acquisition of proximal control, distal control with hemodynamic stability, aneurysm repair, and cautious closure with low threshold for delayed abdominal wall closure. Ruptured aneurysm repair may also be associated with significant coagulopathy, acidosis, and hypothermia requiring significant resuscitation. This resuscitation may predispose the patient to intrabdominal hypertension and ultimately abdominal compartment syndrome requiring abdominal decompression which may be avoided with temporary abdominal wall closure in the initial postoperative period. Aggressive but balanced resuscitation is essential with hypovolemia and the systemic inflammatory response driving the initial resuscitation. Overall systematic and focused repair will maximize results of open repair for ruptured abdominal aortic aneurysms understanding that even with modern medical advances, there remains significant mortality when open repair is required.



Open Repair: Retroperitoneal



Philip S.K. Paty17   and Manish Mehta17 


(17)
Surgery, Albany Medical College, Albany, NY, USA

 



 

Philip S.K. Paty



History and Perspective


Although the usual technique to perform open repair of ruptured AAA has been through a transperitoneal approach, there is a logical thought process that underlies a vascular surgeon’s use of a retroperitoneal exposure. First, the aorta is a retroperitoneal structure. There is, therefore, no need to directly manipulate or avoid bowel or other intraperitoneal structures in order to expose the aorta. Second, exposure of the entire abdominal aorta from the level of the diaphragm to the iliac bifurcation is easily obtained. The surgeon has facile exposure of the paravisceral aortic segment for supraceliac aortic control, clamp placement, and visceral branch reconstruction as necessary. Lastly, there is less physiologic insult to the patient as compared to the transperitoneal approach. This has been debated but is apparent in terms of the duration of postoperative ileus, fluid requirements, and overall length of hospital stay [24].

Initial attempts by surgeons to perform aortic surgery utilized the retroperitoneal approach. Frer and Cooper in 1806 and 1836, respectively, emergently ligated iliac aneurysms using a retroperitoneal exposure [25]. The modern era of aortic replacement was ushered in by Dubost, who performed the first elective aortic homograft replacement of an abdominal aortic aneurysm in 1952 through a retroperitoneal approach [26].

The technique that evolved from this point was mainly an anterolateral exposure as championed by Sir Charles Rob, which was unwieldy for AAA rupture due to difficulty exposing the supraceliac aorta and was largely abandoned during the 1960s and 1970s in favor of transperitoneal exposure [27]. In 1980, Williams reported his use of an extended posterolateral approach for treatment of occlusive and aneurysmal disease of the abdominal aorta [28]. It was this seminal paper that allowed the extensive exposure of the aorta necessary for its use in repair of ruptured AAA.


Surgical Approach



Preoperative Patient Preparation


In general, the prehospitalization and preoperative preparation for the patient with a ruptured AAA is no different for the patient whether a retroperitoneal or transperitoneal exposure is used for repair. Large-bore IV line placement and permissive hypotension are recommended for access and to reduce over resuscitation and operative mortality, respectively. Well-coordinated systems of transfer and communication between emergency field personnel, emergency department, and vascular surgical teams allow the best opportunity for a successful patient outcome. Unless there is a known history of AAA, a preoperative CT scan or Emergency Department FAST ultrasound study is necessary to have a diagnosis of ruptured AAA before utilizing the retroperitoneal technique.


Left Posterolateral Retroperitoneal Approach



Positioning

A suction bean bag (Olympic Vac-Pac) is placed on the operating table before the patient is brought into the operating suite. The patient is initially placed supine on the bean bag. If the patient is hemodynamically stable, large-bore central venous access and peripheral arterial lines are placed prior to induction of anesthesia. Regardless of hemodynamic stability, preoperative antibiotics are given. After the induction of general anesthesia, the patient is rotated into a modified right lateral decubitus position. The patient is positioned with the table break 5–10 cm cephalad to the left iliac crest. The patient’s torso is shifted toward the left and rotated until the left shoulder is elevated 45–60° from the horizontal position while the pelvis is rotated 15–30° to allow access to both groins [29]. The left upper extremity is brought across the chest and supported by blankets, a sling, or a stand. The left thigh is elevated above the horizontal plane to relax the ipsilateral iliopsoas muscle. This maneuver improves access to the distal aorta and left iliac arteries. To open the space between the iliac crest and the costal margin, the table is flexed at the table break (Fig. 13.6). At this point, the operating table should be tilted in a slight reverse Trendelenburg positioning so that the plane of the planned retroperitoneal incision is level.

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Fig. 13.6
(a) Position of patient on operating table. (b) Location of tenth interspace incision (With permission from Darling et al. [35])


Incision

The patient is prepped and draped from the mid chest to the mid thighs bilaterally. Ideally, a self-retaining retractor (Buchwalter) is anchored to the left rail of the operating table. The incision is made sharply from the lateral edge of the ipsilateral rectus muscle between the umbilicus and pubic symphysis in an oblique fashion posteriorly and superiorly through the 10th interspace to the posterior axillary line. The use of this higher incision allows exposure of the paravisceral and supraceliac portions of the aorta.


Initial Exposure and Clamp Placement

The muscle layers of the lateral abdominal wall are divided to the lateral border of the rectus abdominis (incision of the anterior sheath of the rectus allows medial retraction and later exposure of the distal right common iliac artery if needed). The deepest layer, the transversus abdominis, is initially divided laterally and then medially to facilitate separation of the anterior abdominal wall from the peritoneum, which is usually thicker and more discrete laterally. The intercostal muscles are divided on the superior margin of the underlying rib. This incision is carried to the posterior axillary line. Entrance into the pleural cavity is not an issue and can be repaired at the end of the procedure.

In the setting of rupture, the hematoma may have already created the retroperitoneal dissection plane. The initial exposure is performed laterally and posterosuperior to the left kidney so as to avoid manipulation and inadvertent entrance into the cavity of the aneurysm rupture and hemodynamic collapse. The surgeon’s left hand palmar surface is placed on the left psoas muscle and directed cephalad to the posteromedial diaphragm and crus thereby bluntly elevating the peritoneum off the diaphragm. The surgeon should be careful to not violate the fascia overlying the psoas major muscle in order to minimize dissection-related bleeding and cutaneous and genitofemoral nerve injury. The blunt dissection is complete when the supraceliac aorta is palpable beneath the diaphragmatic crus directly on the distal thoracic vertebrae.

At this point, the prime consideration is the placement of the proximal supraceliac aortic clamp. If a self-retaining retractor (Buchwalter) has been placed, the deepest Richardson-type blade is padded with a laparotomy pad and placed to medially retract the peritoneum and its contents so that the diaphragmatic crus is visible. Alternatively, a large deep handheld Deaver retractor is used to obtain the same exposure. Care must be taken to avoid vigorous retraction of the anterior and cephalad margin of the incision as this may result in splenic or renal injury

The initial maneuver to control the supraceliac aorta is to compress it posteriorly with the tips of the fingers of the left hand against the anterior portion of the thoracic vertebrae [29] (Fig. 13.7). The crural fibers are then snipped transversely with a scissors to expose and directly visualize the distal thoracic aorta for clamp placement. A Fogarty clamp should be used as it is relatively less traumatic than a Debakey Aneurysm clamp. The patient should not be heparinized. With experience, the time from skin incision to clamp placement is less than 5 min.

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Fig. 13.7
(a) Left retroperitoneal entry for supraceliac aortic control (With permission from Chang et al. [36]). (b) Manual compression of supraceliac aorta and transverse division of diaphragmatic crus (With permission as above). (c) Supraceliac aortic clamp placement (With permission as above)

At this point, the self-retaining retractor should be placed to allow more stable retraction. The retroperitoneum is widely exposed at this point, and the left kidney is retracted medially and cephalad. All blades used for retraction (rigid or malleable) should be padded to minimize the risk of traction injuries to underlying organs. Care must also be taken by the surgeon to identify the course of the left ureter and thereby avoid the potential for avulsion type injuries.

The surgeon’s attention should be directed to identifying the aortic neck so as to minimize renal and visceral ischemia from the supraceliac clamp. In over 90 % of patients, the aneurysm will originate below the level of the renal arteries. The landmarks for the infrarenal neck of the aortic aneurysm are the origin of the left crus of the diaphragm, the lumbar branch of the left renal vein, and the left renal artery. The lumbar branch of the left renal vein, which crosses the aorta in a posterior and perpendicular fashion and caudad to the left renal artery, should be securely ligated (Fig. 13.8). The lympho-areolar tissue is dissected to expose the proximal infrarenal aorta.

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Fig. 13.8
Lumbar branch of Left renal vein (With permission from Leather et al. [37])

A working knowledge of vena caval and renal venous anomalies is important as one of the major causes of mortality in these cases is due to iatrogenic venous injuries. Failure to appreciate aberrant renal venous anatomy such as retro aortic renal veins or circumaortic renal venous collars or more rarely left-sided or duplicated caval systems may result in significant blood loss. Preoperative CT imaging may identify these types of variant anatomy. If recognized, planned division of the anterior or posterior collar divisions or an approach anterolateral to the aorta may avert catastrophe. Also, the course of the inferior vena cava is such that the separation between it and the aorta is less as it courses in a caudal direction. Thus, injuries to the IVC may occur from the medal extent of the transverse placement of the aortic clamp. Direct injury to the IVC and iliac veins may again be averted with careful dissection on the adventitial surface of the aorta and subsequent clamp placement under direct vision.

Once the neck is identified and dissected free on its lateral anterior and posterior surfaces, the clamp should be placed here but not clamped. The supraceliac clamp should be opened briefly and then the aorta is clamped distally. This will allow any stasis clot proximal to the supraceliac clamp to flush distally and not into the renal and visceral arteries.

If there is no infrarenal aortic neck, the surgeon needs to make a decision whether to perform further dissection of the paravisceral aortic segment along with the renal and visceral arterial branches or to leave the supraceliac clamp in place. My preference is to leave the supraceliac clamp in place and control the celiac, superior mesenteric, and renal arteries.

Distal arterial control is obtained next. The distal aorta, proximal right common iliac artery, and entire left iliac system can be exposed and clamped through the left extended retroperitoneal exposure. If there is significant distal involvement of the distal right common or external iliac arteries, then a small suprainguinal counter incision can be made on the right by a second surgeon to obtain extraperitoneal exposure of the external iliac artery. Alternatively, right iliac artery control can also be obtained with a balloon occlusion catheter through the left flank incision at the time the aneurysm is opened. Additionally, vertical groin incisions can be made to expose the femoral arteries for distal arterial control and anastomosis. As the patient is not systemically heparinized, flushing the outflow arteries with local heparin prior to clamp placement may prevent distal arterial thrombosis due to stasis.


Aortic Reconstruction

The lumbar arteries and the inferior mesenteric artery if they can be identified can be controlled from outside the sac with clips. The sac is then opened with electrocautery, and residual back-bleeding vessels are ligated with 3-0 polypropylene transfixion sutures. The aneurysm neck may be transected completely or partially with the posterior medial wall remaining intact. My preference is to completely transect the aorta to allow precise suture placement through the full aortic wall thickness, thus minimizing later development of pseudoaneurysm. When creating the neck with scissor dissection, the key is to perform the dissection from lateral to medial along the anterior and posterior walls. The surgeon can thus precisely identify the adventitial layer allowing a secure anastomosis.

The type of graft material used is per surgeon’s preference. My preference is to use a tube or bifurcated polytetrafluroethylene graft. The proximal graft anastomosis is performed using a parachuted anastomotic technique with a continuous 3-0 polypropylene suture. The anastomosis starts medially at the 9 o’clock position and is parachuted anteriorly to the 12 o’clock position. At this point, the graft is loosely retracted up anteriorly to allow visualization of the medial and posterior aspect of the aorta to which the graft is sewn next to the 6 o’clock position. The anastomosis is then tightened and the remainder of the anastomosis is completed. Once the suture line is tested, the graft is bled to rid the aorta of any stasis clot, and the clamp is replace on the proximal graft, which is then flushed with heparinized saline.

If an infrarenal anastomosis is not possible, a beveled proximal anastomosis with branch grafts to the involved renal vessels may be necessary. Though the extended left retroperitoneal approach, the entire left renal artery is easily visualized. With further division of the left crus, the lateral pararenal/visceral aorta is well visualized. The right renal artery is best exposed once the aorta has been divided. The right renal artery can be exposed up to its transverse portion beneath the inferior vena. Control of the left renal artery is best obtained with Yasargil-type neurosurgical clamps. The right renal artery is best controlled with “C”-shaped curved Cooley clamp.

If possible, it is best to bevel the visceral segment and reconstruct the renal vessel(s) with separate 6–8 mm end-to-end anastomoses, which are pre-sewn onto the main body of the aortic graft. The proximal aortic anastomosis to the paravisceral aortic segment is performed first. The aortic clamp is then repositioned from the native aorta to the proximal graft after flushing the graft as previously detailed to allow perfusion of the visceral and renal arteries. The anastomosis to the renal arteries is performed next in a spatulated end-to-end fashion with 6-0 continuous polypropylene sutures. Once this is completed, the aortic graft is clamped below the lower most renal graft limb.

Next the distal aortic, iliac, or femoral anastomoses are completed. The distal graft limbs of the graft are tunneled anatomically along the axis of the vessels. On occasion, this may not be possible for limbs tunneled from within the left flank incision to distal exposure of right iliac or femoral arteries due to inflammation or prior surgery. In this situation, the right limb graft limb can be tunneled via the preperitoneal prevesical space of Retzius. Prior to performing distal anastomoses, embolectomy catheters should be passed distally intra-arterially to retrieve any stasis thrombus, 4 French for iliac and 3 French for femoral arteries. The distal arteries should then be flushed with heparinized saline and re-clamped. Once the distal anastomoses are completed, the clamps are removed and Doppler interrogation is performed.

If there is any concern regarding intestinal viability or traction injury to the spleen, the peritoneum can be purposefully incised to allow for direct inspection of the intra-abdominal contents. At this point, any defects in the peritoneum are repaired. If entrance into the pleural cavity does occur, it should be fixed directly upon incision closure by sewing the cut diaphragmatic edge to the next highest rib while catheter suction is maintained in the pleural cavity. Alternatively, tube thoracostomy can be placed. The abdominal wall musculature is closed in layers followed by closure of the subcutaneous tissue and skin. Closure of the wound is made easier by taking the flex out of the table, which allows a tension free repair.


Retroperitoneal Exposure for Secondary Rupture After EVAR


Surgical conversions following EVAR have been described by a few centers, all utilizing the standard transperitoneal approach via midline laparotomy [30, 31]. The retroperitoneal approach to the abdominal aorta as described for open repair of ruptured AAA can be easily utilized for secondary AAA rupture after an EVAR with explant of the endovascular graft. A surgeon’s familiarity with the extended left retroperitoneal exposure in elective situations involving infrarenal, juxtarenal, and pararenal abdominal aortic aneurysms may allow one to extend the use of this approach to more complex clinical scenarios. The same attributes of the left retroperitoneal exposure that facilitate repair in ruptured aneurysm, such as the ability to control the entire abdominal aorta from the distal thoracic segment to the iliac bifurcation, apply to open repair in patients with rupture after failed endovascular repair [32].

The positioning, incision, and exposure are identical to the technique for repair of ruptured AAA detailed previously. The degree of difficulty in exposing the operative field in the retroperitoneum in the setting of a previously deployed aortic endograft varies depending upon the amount of inflammation present, which is due either to the mere presence of the endograft within the aorta or a reactive response to prior attempts at translumbar coil embolization of persistent type I or II endoleaks. The appearance may resemble that of an inflammatory aneurysm; therefore, maneuvers to minimize injury to adjacent structures (duodenum and renal veins), such as maintaining the dissection within the retroperitoneum as posterior as possible, and attempts to identify the ureter early with or without the use of preoperatively placed stents may facilitate the procedure. The supraceliac aortic dissection is usually free of inflammation, whereas the infra- and juxtarenal portions of the aorta are often significantly inflamed rendering the dissection hazardous. The safest method is to approach the lateral and posterior aspect after initial clamp placement. Another alternative is to obtain control with an intra-aortic balloon directed from one of the femoral arteries and inflated at the supraceliac aortic level.

If further dissection of the aortic neck cannot be safely performed, the initial supraceliac aortic clamp is left in place, distal clamps are placed, and the aneurysm sac is opened. If information is available regarding the previously deployed endograft in terms of suprarenal versus infrarenal fixation, this may help plan subsequent control and clamping of the distal aorta. In patients with a known suprarenal fixation, it is often preferable to leave the aortic cross clamp on the supraceliac aorta. With a known infrarenal device, assuming the aorta can be accurately dissected, is minimally diseased and has no significant aneurysmal component, the cross clamp can be moved to the infrarenal aorta.

The single most important factor in deciding between partial and complete stent graft explant is whether the endograft can be completely removed without destroying the aortic wall (Fig. 13.9). The surgeon needs to remember that the goal is to control bleeding and reconstruct in line flow as expeditiously as possible. Other considerations include the type of stent graft fixation (suprarenal versus infrarenal and active with hooks/barbs vs. passive with self-expanding stent only), as this may influence the site of aortic clamping and the possible adjunctive need for visceral endarterectomy and/or revascularization with complete stent graft explant. Infrarenal aortic clamping with only partial stent graft explant might be a significantly less morbid procedure when compared with supraceliac aortic clamp and complete stent graft explant, with possible visceral reconstructions, particularly in the patient with aneurysm rupture [33]. In cases of rupture secondary to a type IA endoleak, the proximal endograft may slide out easily. Lastly, some endografts with suprarenal fixation can be “captured with a cut syringe barrel, thereby facilitating explant [34].

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Fig. 13.9
(a) Complete endograft explant. (b) Infrarenal aortic replacement with prosthetic graft

In AAA rupture patients with infrarenal stent grafts, the proximal aortic clamp is placed at the suprarenal level, the aneurysm sac is opened, the entire infrarenal stent graft can be explanted including the iliac limbs, and aortoiliac reconstruction is performed as needed (Fig. 13.9). In AAA rupture patients with suprarenal self-expanding stents for fixation, aortic control is obtained by placing a supraceliac aortic clamp. In these cases, partial stent graft explant with transaction of the stent graft within the proximal aortic neck is performed. In AAA rupture patients with stent grafts that have had placement of proximal Palmaz stents, aortic control is obtained via a supraceliac aortic clamp, or an aortic occlusion balloon, with partial or complete stent graft explant. When the proximal aortic stent graft is partially explanted, the proximal graft is sewn to the composite endograft/proximal aorta with or without pledgets depending on the friability of the aortic wall (Fig. 13.10). Renal arterial reconstruction may be necessary as previously detailed depending upon the wall integrity and extent of the proximal aortic aneurysm (Fig. 13.11).

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Fig. 13.10
Partial proximal endograft explant after aortic reconstruction


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Fig. 13.11
(a) Complete endograft explant and left renal artery bypass. (b) Complete endograft explant and bilateral renal artery bypass (Note: renal grafts offset to allow sequential renal reperfusion)

If the entire distal portion of the endograft can be removed, the aortic graft is sewn to the aorta, iliac, or femoral arteries depending on the extent of aneurysmal and occlusive disease. In instances when the iliac limbs cannot be explanted due to scarring, either the distal anastomosis is constructed beyond the iliac stent grafts or the aortic bifurcation is then oversewn (Fig. 13.12), or the limbs are transected at the aortic bifurcation, and the aortic tube graft is sutured directly to the distal aortic bifurcation, and the stent graft limbs are incorporated within the anastomosis. Alternatively, the limbs of a bifurcated graft can be sewn individually to the remaining endograft limbs or the distal body of the endograft (Fig. 13.13). Interrupted 5-0 polypropylene sutures are then used to secure the native distal iliac arteries to the distal portion of the remaining EVAR limbs.

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Fig. 13.12
Partial distal endograft explant with end-to-side distal reconstruction


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Fig. 13.13
Partial distal endograft explant with anastomosis to residual endograft (Note: interrupted sutures to secure iliac limbs to native iliac arteries)


Conclusion


The extended left retroperitoneal approach can be used to perform open repair of de novo ruptured AAA or after delayed rupture of the AAA sac after EVAR. The ideal method to incorporate the technique is through experience with elective repair. The ability to directly deal with the aortic reconstruction without the need to pay attention to intraperitoneal structures is the principle advantage of this technique.


Rupture EVAR Using Bifurcated Stent Grafts



Manish Mehta18, 19   and Philip S.K. Paty18


(18)
Surgery, Albany Medical College, Albany, NY, USA

(19)
Vascular Health Partners, CCP, Gloversville, NY, USA

 



 

Manish Mehta



Introduction


The metamorphosis of rAAA treatment from open surgical repair to EVAR has evolved significantly over the past two decades from being performed selectively by a few centers in hemodynamically stable patients only to being performed by most endovascular specialists in many centers in patients with varying degrees of hemodynamic instability [3840]. Collectively, worldwide experience demonstrates that an increasing number of rEVAR procedures are being performed yearly. The endovascular approach is less invasive, eliminates laparotomy, eliminates aortic cross clamping, decreases surgical bleeding and possibly general anesthesia, and has been shown to decrease the mortality of rAAA repair with fewer complications, shorter hospital length of stay, and more patients being able to return home rather than going to institutional care after these emergent procedures [41, 42]. Factors that influence institutions ability to offer rEVAR to patients include not only established infrastructures that can provide comprehensive care for rAAA patients but also well-trained surgeons/interventionists that can perform complex endovascular aortic procedures in emergent circumstances using currently available devices. This chapter will focus attention on the use of modular bifurcated stent grafts for managing patients with rAAA.


Approach to Ruptured EVAR


Introduction of EVAR for rAAA has forced us to reevaluate protocols that facilitate expeditious patient transfer to the operating rooms for EVAR or open surgical repair. Today, the question is not whether patients with rAAA should undergo EVAR rather how to develop systems that allow for broader utilization of these complex procedures that have shown great benefit in high-risk patients with aneurysm rupture. This chapter focuses on the use of modular bifurcated stent grafts for rEVAR; there are several additional aspects that merit discussion as they have an impact on procedure technical aspects, including standardized protocol-based approach to rAAA, anatomic suitability for rEVAR, choice of anesthesia, percutaneous vs. femoral cutdown approach, bifurcated vs. aorto-uni-iliac stent grafts, and the implications of using aortic occlusion balloon during rEVAR.

There remain several fundamental concerns regarding EVAR for rAAA that include the anatomical suitability for EVAR, the availability of dedicated staff and equipment to perform emergent EVAR at all hours, the feasibility of treating hemodynamically stable and unstable patients by EVAR, and the surgeon/interventionists’ ability to manage unexpected scenarios under emergent circumstances [43, 44]. Many of the high-volume institutions have adopted a standardized protocol-based approach to managing rAAA patients [45]. The hemodynamic status of the rAAA patient generally dictates the need for a preoperative CT scan, and although while planning for this emergent open surgical repair, a preoperative CT is not considered a necessity, while planning an emergent EVAR, most would agree that we would like to have a CT scan for evaluating the feasibility of EVAR as well as for stent graft sizing. So the question is whether one has the time to get an emergent CT scan prior to EVAR, and if not are there other tools available that might help us manage these hemodynamically unstable patients by endovascular means? Published data on the feasibility of preoperative CT in patient with rAAA would indicate that 88 % (49 of 56) of the patients died >2 h after admission with the diagnosis of ruptured AAA, the median time interval from the onset of symptoms to admission to the hospital was 2.5 h, and the interval between hospital admission with the diagnosis of ruptured AAA and death was 10.5 h [46]. This data would clearly suggest that majority of the patients with ruptured AAA have the time to undergo an emergent CT scan, particularly if there is an established protocol that facilitates early diagnosis and transfer of patient from the ER to the OR.

The proportion of rAAA patients that are suitable for EVAR is variable and on the basis of two meta-analysis ranges from 47 to 67 %. What has also been reported is that when compared to elective AAA, rAAAs have larger infrarenal aortic diameters and shorter neck lengths. These differences in AAA morphology likely have an effect on the ability to perform rEVAR, and it is likely that institutions that treat a higher proportion of rAAA by EVAR expand on the stent graft indications for use of these high-risk patients [47]. Several institutions including ours have tried to identify the impact of rEVAR in patients with favorable versus unfavorable aortic neck morphology [48, 49]. We further analyzed aortic neck morphology via CT scans in 180 consecutive patients with rAAA that underwent rEVAR (74, 41 %) or OSR (106, 59 %) [50]. Based on EVAR device-specific favorable versus hostile aortic neck morphology, we identified that only 34 % of patients with rAAA had neck morphology that would meet the “indication for use” for available stent grafts. The rEVAR patients with hostile aortic necks had a significantly higher incidence of female gender (32 % vs. 19 %, p < 0.01), mean maximum AAA diameter (7.4 cm vs. 5.5 cm, p < 0.01), abdominal compartment syndrome (20 % vs. 4 %, p < 0.01), type I endoleaks (16 % vs. 4 %), and the need for all secondary interventions (77 % vs. 40 %, p < 0.01) during long-term follow-up. The 30-day mortality was the lowest in rEVAR patients with favorable aortic necks and the highest in the OSR patients (favorable 8 %, hostile 23 %, OSR 43.4 %, p < 0.01), and both favorable and hostile rEVAR patients had a better cumulative 3-year survival than OSR (favorable 64 %, hostile 67 %, OSR 44 %, p < 0.01). Mayer et.al. reported their experience of 473 rAAA patients where over time they transitioned to rEVAR in 100 % of patients with rAAA [51]. This was the first study to address the outcomes of complete replacement of all rAAA to be treated from open surgical repair to rEVAR. Their findings suggested that nearly all patients with rAAA can undergo rEVAR with a low mortality of 24 % and a low turndown rate of 4 %. However, with transition to rEVAR for all patients, surgeons/interventionists and institutions also need to have the ability to manage more challenging anatomy and comfortably utilize adjunctive endovascular techniques in managing the hostile proximal landing zones.

Depending on one’s comfort level and the logistics, EVAR for rupture can be performed under local anesthesia via percutaneous approach to general anesthesia and femoral artery cutdown. The potential benefit of local anesthesia/conscious sedation and percutaneous approach is that it might avoid the loss of “sympathetic tone” in the compromised ruptured AAA patients. One has to be comfortable with obtaining percutaneous access and using closure devices in patients that might be hemodynamically unstable with difficult to palpate femoral pulses. Although the advantage may be significant, it must be balanced by the potential difficulties encountered during these emergent procedures, as the patient might not be coherent and cooperative enough to lie still. The potential advantages of using modular bifurcated stent grafts over aorto-uni-iliac devices are that it allows for cases to be done via percutaneous approach with local anesthesia and femorofemoral bypass is not needed.


Endovascular Setup and Techniques


Adequate resuscitation of patients with ruptured AAA is vital to a successful outcome. As long as the patients maintain a measurable blood pressure, the techniques of “hypotensive hemostasis” by limiting the resuscitation to maintain a detectable blood pressure can help minimize ongoing hemorrhage. The patient is prepped and draped in supine position, and via a percutaneous or femoral artery cutdown, ipsilateral access is obtained using a needle, floppy guidewire, and a guiding catheter. The floppy guidewire is exchanged for a super-stiff wire that can be used to place a large sheath (12–14 Fr × 45 cm length) in the ipsilateral femoral artery and the sheath advanced up to the juxtarenal abdominal aorta so it is ready to be used to deliver and support the aortic occlusion balloon if needed. A compliant occlusion balloon should always be available in these procedures, and in hemodynamically unstable patients, the occlusion balloon is advanced through the ipsilateral sheath over the super-stiff wire into the supraceliac abdominal aorta under fluoroscopic guidance, and the balloon is inflated as needed [52]. For detailed discussion on aortic occlusion balloon use, see Chap. 12. Contralateral femoral access is subsequently obtained via percutaneous or cutdown approach in a similar fashion and a “marker flush catheter” advanced to the juxtarenal aorta for an arteriogram.


Ruptured EVAR Using Bifurcated Stent Grafts


As expected, the emergence of EVAR has also resulted in the evolution of stent graft design. A detailed discussion on stent graft design is well beyond the scope of this chapter, but one has to consider the various stent graft configurations available when performing rEVAR. The stent graft best suited for managing rAAA is likely the one the operator is most comfortable using in elective circumstances. With that said, there are several implications of stent graft design that might impact rEVAR under emergent circumstances, and since there is no evidence in literature evaluating the validity of one stent graft over another in managing rAAA, maybe it is best to understand some of these nuances that might have advantages under emergent circumstances. Bifurcated stent grafts can be divided into several categories based on their fixation (suprarenal vs. infrarenal), modularity (one docking limb vs. two docking limbs), and sealing mechanism (stent + graft vs. polymer + graft). Regardless of the design and improvements in lower profile delivery systems, controlled deployment mechanisms, and active fixation methods, it is also clear that bifurcated stent grafts perform significantly better when they are used to treat anatomy within its “indications for use” (IFU) [53]. Unfortunately, high-risk patients with rAAA require quick response to stop the hemorrhage, and operators are sometimes forced to perform emergent rEVAR under unfavorable circumstances and sometimes require the use of aortic occlusion balloon. In such conditions, factors to consider should include the implications of need for aortic occlusion balloon with (1) suprarenal vs. infrarenal fixation stent grafts and proximal aortic neck angulation and morphology, (2) aorto-uni-iliac vs. modular bifurcated stent grafts with one or two docking limbs, (3) polymer-based devices and the time requirements for polymers to cure and seal the aortic neck, and (4) the need for adjunctive procedures including single or multiple chimneys for visceral arteries, the use of Palmaz stent or EndoAnchors for proximal seal, femorofemoral bypass, and the need for iliac artery occlusions depending on the planned procedure.

The decision to use a particular stent graft type is determined by the patient’s aortoiliac morphology, and there are several factors to consider regarding the use bifurcated vs. aorto-uni-iliac stent grafts for rAAA: (1) inability to access the contralateral gate expeditiously and (2) inability to access the contralateral iliac artery due to significant occlusive disease and/or tortuosity. The use of aorto-uni-iliac devices during elective or emergent EVAR does require interruption of flow from the contralateral common iliac artery into the AAA via a placement of an occluder device and a femorofemoral bypass. Several studies have documented the use of aorto-uni-iliac devices for rEVAR with outcomes similar to the use of bifurcated stent grafts. It is likely that the use of aorto-uni-iliac devices might expand on the applicability for rEVAR [54, 55]. For more on the use of aorto-uni-iliac stent grafts for rEVAR, please see the next chapter by Ian Loftus.

The placement of the stent graft main body is planned based on the aortoiliac morphology that is best suited for rEVAR. Unless prohibited, in hemodynamically stable patients, following the initial arteriogram, the aortic occlusion balloon is removed from the initial ipsilateral side and the stent graft main body advanced under fluoroscopic guidance; this limits the number of catheter exchanges. In hemodynamically unstable patients that require inflation of the aortic occlusion balloon, the “marker flush catheter” is exchanged for the stent graft main body which is delivered up to the aortic neck. An arteriogram is done via the sheath that is used to support the aortic occlusion balloon, the tip of the stent graft main body is aligned with the lowermost renal artery, the occlusion balloon is subsequently deflated and withdrawn back with the delivery sheath into the AAA, and the stent graft main body is deployed. In the rare instance when patient’s hemodynamic status is extremely compromised and the aortic occlusion balloon cannot be deflated, there are several alternatives to consider. The sheath housing the aortic occlusion balloon should be advanced to a level above the renal arteries and the stent graft deployed at the infrarenal level. This maneuver allows for the occlusion balloon to be deflated and retrieved into the sheath without compromising the proximal stent graft fixation and seal. In these particular situations, one needs to consider the use of aorto-uni-iliac stent grafts or the conversion of bifurcated devices to aorto-uni-iliac to avoid further delays in obtaining proximal stent graft seal while cannulating the bifurcated stent graft contralateral gate. The alternative is to communicate with the anesthesiologist so they can manage the patient’s hemodynamics, deflate and withdraw the aortic occlusion balloon, and deploy the main body-bifurcated stent graft. Then expeditiously from the main body ipsilateral side advances the aortic occlusion balloon over the wire up to the aortic neck and inflate. This maneuver allows for the seal of the stent graft at the proximal aortic neck while reestablishing proximal occlusion at the aortic neck within seconds. This temporary deflation of the aortic occlusion balloon rarely results in hemodynamic collapse and usually is of little consequence. Of importance is to recognize that once the occlusion balloon is reinflated within the bifurcated main body, it requires gentle forward traction to counteract the downward traction from forces of the systolic blood pressure which if left to itself could result in prolapse of the main body stent graft distally into the AAA. The exact steps here might vary depending on the use of bifurcated stent grafts with suprarenal vs. infrarenal fixation and modular components that have a single docking vs. two docking limbs. Depending on what particular bifurcated device one is comfortable using, one needs to rehearse the steps and plan accordingly. Finally, the occlusion balloon inflated and secured within the proximal bifurcated main body creates a more hemodynamic stable environment for the patient and allows us to move onto the next steps which include contralateral gate cannulation. The remainder of the rEVAR procedure is performed similar to as in elective circumstances; following contralateral gate cannulation, appropriately sized iliac stent graft extensions are advanced and deployed as needed to obtain complete aneurysm exclusion.


Expanding the Proximal Stent Graft Landing Zone for Ruptured Pararenal AAA


In addition to treating ruptured infrarenal AAA, bifurcated stent grafts have also been used for managing ruptured pararenal AAA with the addition of adjunctive chimney procedures – EVAR [51, 56]. Currently published data is limited and would suggest that adjunctive chimney techniques with the use of bifurcated stent grafts likely allows a higher percentage of rAAA patients to be treated by endovascular means, but it is also likely that the resultant type I endoleaks and overall mortality will also be higher. When planning these emergent procedures, we need to be vigilant in understanding some of the nuances of the available evidence and in planning these complex procedures.


Rupture After EVAR


The goal of AAA repair is to reduce the risks for aneurysm rupture and death. However, none of the currently available stent grafts is completely effective in preventing aneurysm rupture after EVAR, and lifelong surveillance is needed. We evaluated our experience of delayed AAA rupture after EVAR and found that the most common risk factors contributing to rupture included type I endoleaks with stent graft migration (63 %), type I endoleaks without stent graft migration (11 %), type II endoleaks (19 %), and undetermined etiology (7 %). In this series, 41 % of patients with rAAA after EVAR underwent another EVAR procedure with an operative mortality of 9 %, whereas 55 % required conversion to surgical repair with an operative mortality of 20 % [57].

Although bifurcated stent grafts might have a role in managing rupture after EVAR, stent graft migration from proximal fixation sites and type I endoleaks remain the most common cause of rupture after EVAR [58]. In these circumstances, bifurcated stent grafts are infrequently needed, and most patients require proximal stent graft extensions with or without chimney or fenestrated stent graft use to lengthen the proximal stent graft seal zone. If bifurcated stent grafts are the only available devices in such emergent circumstances, they can be utilized to advance the proximal landing zone and convert the original bifurcated stent graft into aorto-uni-iliac configuration, as needed (Figs. 13.14 and 13.15)

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Fig. 13.14
Bifurcated stent grafts for ruptured EVAR and use of aortic occlusion balloon (AOB). (a) Bifurcated stent graft advanced to the level of the lowermost renal arteries, and occlusion balloon advanced from contralateral side and inflated at supraceliac aorta. (b) Deflate and retrieve the AOB and deploy the bifurcated stent graft. (c) Advance the AOB from within the stent graft main body and inflate at the level of the aortic neck. (d) Cannulate bifurcated stent graft contralateral limb with occlusion balloon maintaining aortic occlusion and apply forward traction on AOB catheter to prevent AOB and stent graft prolapse into the aneurysm. (e) Completion arteriogram following ruptured EVAR with bifurcated stent graft


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Fig. 13.15
Post-op CTA following ruptured EVAR with bifurcated stent graft


Conclusions


Endovascular repair of rAAA is evolving and offers the potential for improved patient survival. Unlike elective EVAR, during emergent EVAR, the time for preoperative planning is limited, and often the preoperative imaging is less than ideal; under these circumstances, one often has to get creative and utilize more of a “problem-solving approach” to address challenging issues that might arise during these emergent circumstances. A standardized multidisciplinary approach can be instrumental in organizing pathways that can accommodate individual practices and hospital infrastructure and facilitate a seamless transition of these often hemodynamically unstable patients from the time of diagnosis to successful rEVAR. There are several important technical aspects including the choice of anesthesia, percutaneous vs. femoral cutdown approach, use of aortic occlusion balloons, use of bifurcated vs. aorto-uni-iliac stent grafts, and adjunctive procedures that need to be well understood as one embarks on performing these procedures.


EVAR-AUI: The European Experience



Ruth  A. Benson20, S. Bahia20, R. J. Hinchliffe20 and I. M. Loftus20  


(20)
Albany, NY, USA

 



 

I. M. Loftus



Introduction: The Origins of the AUI Graft


The first English language report into the use of a balloon expandable aorto-uni-ilac (AUI) stent for AAA management was published in 1991 [73] (Fig. 13.16), although it had already been reported in the Russian literature in 1988 [82]. Parodi’s novel method described the use of a balloon expandable stent loaded onto a deployment device and inserted into the aneurysmal aorta via retrograde femoral artery access. This was accompanied by contralateral iliac occlusion and a femorofemoral crossover graft. Designed to exclude the aneurysm, they described initial clinical success in 5 patients, all of whom had been denied open repair due to significant comorbidity.

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Fig. 13.16
The Parodi-Palmaz device. The Palmaz stent was sutured to a dilated PTFE graft [70]

Encouraged by this early experience, surgeons in Europe began to create their own versions of the graft. Published results of small UK-based series followed. The Leicester group reported their initial experiences in 1997 [79], with a refined method using an 8-mm pre-dilated PTFE tube graft with the addition of a proximal Palmaz stent, mounted onto a 30-mm balloon. They described successful deployment in 20 patients, providing clear accounts of the complications they encountered. Initial results were positive, but long-term efficacy was yet to be proven.

Results from larger UK and European cohorts followed, all supporting the feasibility of endovascular AUI aneurysm repair. Survival in elective patients was reported as 90 % at 4 months, even among high-risk patients. Overall, the merits of the AUI graft were becoming increasingly apparent [64]. They were readily custom-made by the surgeon. Access and deployment were simple, using preexisting technology and equipment. It was becoming apparent that there was an emerging role in the treatment of patients with significant comorbidity for whom open repair was not an option. It was suitable for AAA where anatomy was more complex or where there were tortuous or unilaterally occluded iliac arteries.

Initially as bifurcated devices were designed, the AUI technique maintained superiority, the perceived advantage being the range of patients in whom it could be implanted. In a review of 154 AAA CT scans, Armon et al. found 55 % of patients were suitable for implantation of an AUI graft, compared to only 10 % for an early bifurcated endograft [60]. Investigators in the Amsterdam Acute Aneurysm Trial found that 45.8 % of patients presenting with ruptured AAA (rAAA) were suitable for AUI, while others found only 20 % of ruptures were suitable for bifurcated grafts [70, 76]. These data was applicable to the endografts available to the authors at the time and would not be representative of the range of devices now available.


The European Experience: Graft Complications


An increase in the number of surgeons adopting AUI was followed by the identification of novel complications linked both to the learning curve and to the specifics of the grafts themselves. Ivancev’s report of his group’s experiences in 45 patients detailed a variety of complications. Early issues included insertion of endografts that were too short (necessitating conversion to open repair), iatrogenic renal artery occlusions, graft kinking, iatrogenic iliac dissection, and type 2 endoleaks [71]. Mortality remained high, as these were patients selected because their comorbidity precluded open repair (OR). At 1 year, surveillance identified significant stent migration in 5 patients and the presence of type 2 endoleaks in 3 requiring embolization.

Despite routine femorofemoral crossover graft, some patients developed significant buttock claudication [72]. Indeed the requirement for a crossover graft raised the most doubts about the longevity of AUI as a procedure despite evidence suggesting better durability in aneurysmal compared to occlusive disease [84].

Relatively favorable rates of early complications of femorofemoral crossover bypass grafts were documented in a study of 136 elective patients treated with AUI in Nottingham [83, 84]. Frequency of groin or graft infection was found to be equivalent to bifurcated devices. Further publication of a larger cohort, an 8-year experience in 231 patients, demonstrated an infection rate of 11 %, a cumulative 3-year patency rate of 91 %, and 5-year patency of 83 % [67]. Importantly, their large case series enabled them to identify factors promoting graft occlusion, mostly related to technical issues with the AUI. However, patency rates remained comparable with those reported following OR and bifurcated grafts.


“Peri-graft Extravasation”: The Risk of the Endoleak and Surveillance


First proposed by White, the terminology now used when classifying endoleaks has become ubiquitous in the setting of endovascular AAA repair [85]. Endoleaks remain the most common indication for reintervention following EVAR, and the early adopters of AUI began to address the design of surveillance programs. Initially, CT imaging was the only established method for identifying stent migration or leak, but valid concerns regarding mounting costs and risks of cumulative radiation exposure were raised. In their prospective study of aneurysm morphology and radiological and ultrasound appearances following AUI repair, the Leicester group compared the ability to identify AAA migration or peri-graft extravasation (endoleak) 6 weeks postimplantation using CT and duplex ultrasound. They found duplex to be comparable, and in some cases superior, due to its less invasive nature, lower cost, and greater effectiveness in identifying the site of endoleak [80]. Attempts to predict the risk of endoleak preoperatively based on CT imaging were unsuccessful, with a lack of correlation between the number of patent lumbar or inferior mesenteric arteries and risk of endoleak [83, 84]. The need for postoperative surveillance was firmly established.


AUI and the Ruptured AAA: A Victim of Its Own Success


The success of AUI in patients with poor physiological status meant that progression to its use for rAAA was inevitable. Successful deployment was first published by Yusuf et al. in 1994 [87]. This group published early results of their surgeon-manufactured endografts in 30 patients including a further 2 rAAA using a modified Gianturco (self-expanding) stent, Dacron graft, and Wallstent [86]. The graft was preloaded onto either the Chuter (18 F, 5/30) or the Ivancev delivery system (20 F, 25/30 cases).

In a setting where mortality for rAAA had been persistently high for decades, endovascular repair with the AUI technique offered hope for radically increasing patients’ chances of short-term survival [59]. One particular advantage was seen as the AUI’s ability to gain rapid hemostasis without laparotomy and anatomic applicability over a relatively large proportion of patients. The technique was thought to create far less of a physiological insult, although much like EVAR today, selection bias toward more frail patients meant that outcomes were not as positive as some had predicted [64].


AUI Devices/Occluders/Technique


A number of AUI devices have been used to treat aneurysmal aortic disease over the years (Table 13.1); however, the technique for intervention remains broadly similar, i.e., insertion of an occlusive aortic balloons depending on the hemodynamic state of the patient, followed by deployment of the AUI device (Fig. 13.17), and insertion of an occluder for a patent contralateral iliac system and a crossover graft [68]. Several occluder devices have been utilized in the literature, including the Talent device (Medtronic, nitinol, woven polyester, 8–24 mm distal diameter, 31–35 mm stent length, 17.5 F delivery system), the Zenith iliac plug (Cook, 14–24 mm diameter, 30 mm length, 14–16 F delivery system), as well as AMPLATZER plugs (St. Jude Medical, 3–22 mm, 7 F) for particularly small iliac vessels [63].


Table 13.1
Aorto-uni-iliac grafts used in European centers performing endovascular AAA repair














































Stent graft

Construction

Proximal diameter (main body)

Distal diameter (main body)

Sheath size

Comments

Endofit (LeMaitre vascular)

Self-expanding, nitinol, PTFE, 2 layers

20–36 mm

12–20 mm

18 or 22 F, hydrophilic

10–20 cm length

Talent (Medtronic)

Self-expanding, nitinol, polyester fabric

22–36 mm

14–16 mm

22 or 24 F

Bare-spring proximally (if >22 mm) to pararenal placement

Endurant (I/II) (Medtronic)

Self-expanding, nitinol, suprarenal fixation

23–36 mm

14 mm

18 F or 20 F

102–5 mm of graft covered

Zenith (Cook)

Self-expanding, stainless steel and nitinol, braided polyester, suprarenal fixation

24–36 mm

12 mm

20 F

Distal components 12–24 mm diameter


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Fig. 13.17
Post-EVAR digital subtraction angiogram with contralateral common iliac artery occluder [74]

Alsac’s group in France published outcomes for 37 consecutive patients presenting with rAAA over a 4-year period [59]. From a cohort of 17 patients treated with EVAR, 8 were managed with AUI (a mix of Cook and Medtronic grafts). Patients were not randomized – EVAR was attempted if possible, but in those with hemodynamic instability, open repair (OR) appeared to be the first choice. Overall, operating time was significantly less in the combined EVAR group, with reduced blood loss and length of intensive care stay. Interestingly, on retrospective analysis, 73 % of the patients who were treated with OR due to “unfavorable anatomy” were actually suitable for EVAR. The 30-day mortality following EVAR was also lower at 23.5 % vs. 50 %, although this narrowly missed reaching statistical significance.

Several interesting points were raised by this study. By 2005, the ability to perform bifurcated EVAR under local anesthetic was well established, and the authors confirmed that their own experience had begun with bifurcated grafts. Their use of AUI followed a change in practice for those patients requiring extremely quick hemorrhage control or those with complex anatomy. They noted that the need for crossover grafts necessitated a conversion to general anesthesia after aneurysm sealing, with associated additional risks and often prolonging surgery beyond that of bifurcated stents.

Attempts to run randomized studies followed soon after. The Nottingham-based pilot study comparing AUI (two-part Gianturco stents with uncovered suprarenal component) with OR was designed to include a cohort who were considered fit for either form of repair in an attempt to reduce patient selection bias [66]. Their technique allowed for the initial procedure to be performed under local anesthetic, after which patients were fully anesthetized prior to stent deployment (Fig. 13.18). This followed experiences with severe ischemic pain from the occluded limb. The contralateral iliac artery was occluded with the Zip plug (Cook Europe, Copenhagen, Denmark or Endomed, Arizona, USA). In total, 103 patients were admitted with suspected ruptured AAA, but selection criteria meant that only 11 completed AUI and 12 OR. Results were similar for both in terms of complication rates, median hospital stay, and time from admission to surgery. The authors expressed disappointment that AUI didn’t seem to confer significant improvement. However, their success in piloting one of the first pragmatic randomized trials for management of rAAA was laudable.

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Fig. 13.18
Successfully excluded rAAA with AUI [65]

The BiFab study investigated the use of a modular AUI stent graft using off-the-shelf stock of four body and four limb sizes (compared to over 600 various components making up bifurcated kits) [69]. Sixty-five patients presenting with either symptomatic or ruptured infrarenal AAA were recruited from seven European centers [69]. Aneurysm exclusion was complete in a median time of 40 min, with a blood loss of only 200–800 ml. Despite this, perioperative mortality remained high at 40 %, and overall procedure time was longer than reported times for bifurcated grafts. The authors highlighted that other techniques such as aortic balloon occlusion allow for more rapid hemostatic control, after which there is more time for either technique to be used. They also encountered several operator-specific complications such as overstenting of the renal arteries and catching of the graft on the sheath, although this did not appear to translate to increased need for reintervention at 1-year follow-up.

Other trials comparing EVAR with OR in rAAA included both bifurcated grafts and AUI, which indicated the direction of trends for endovascular repair. The French ERA trial included 150 patients in its EVAR arm, with a variety of procedures and grafts used [61], although the trial did not demonstrate any significant differences between EVAR and OR even for EVAR patients stratified as low or intermediate risk for OR.

Another earlier multicenter study evaluating outcomes in 26 patients undergoing EVAR vs. 29 undergoing OR demonstrated a similar 30-day mortality and complication rate, a pattern that persisted to 1 year [81]. These authors specifically stated a preference for bifurcated grafts, unless anatomy dictated an AUI, and this only applied to one out of 26 patients.

Despite the clear rise in user preference for bifurcated grafts as first-line EVAR in ruptures, European trials testing various AUI devices for rAAA continued. The ERA trial enrolled 100 consecutive patients across 10 institutions (49 AUI and 51 OR) [74]. As in previous trials, authors commented that there was no difference between preoperative comorbidity and hemodynamic status between the two groups, to refute any suggestion of selection bias. As with previous studies, AUI led to less blood loss and shorter duration of stay in intensive care. Despite this, differences in in-hospital/30-day mortality (35 and 39 % respectively) and 3-month mortality (40 % and 42 % respectively) were equivocal. One of the significant findings of the study was the fact that AUI was suitable in at least 50 % of patients presenting with rAAA. The Amsterdam Acute Aneurysm Trial collaborators, in another randomized control trial, reported a 30-day mortality of 21 % for AUI and only 25 % for OR [75]. Although there still didn’t appear to be a significant difference between the two surgical modalities, relative improvements in early outcomes following all ruptures demonstrated the benefits of dedicated vascular centers providing a 24-h endovascular and specialist vascular service.

The more recent IMPROVE trial confirmed these ongoing short-term improvements in outcome, but did not report on differences in results between patients having AUI and bifurcated grafts [65].


Bifurcated Grafts Versus the AUI


There are few studies directly comparing results of bifurcated and AUI grafts, perhaps due to the now clear preference for the bifurcated graft among endovascular specialists. The benefits of AUI, namely, quicker exclusion of the aneurysm sac, often led to its use in more unstable patients with unfavorable anatomy, thus skewing results and deterring surgeons from using it as a first-line graft. Carrafiello observed higher mortality following AUI for rAAA, but also demonstrated that poor hemodynamic state had the greatest negative effect on survival and suggested that AUI was used preferentially in this group to get rapid hemostasis [61].

Results from the ENGAGE registry looking at outcomes for elective AAA reviewed outcomes in 1172 patents, in which only 7.1 % were treated with AUI [78]. The authors noted a higher rate of cardiopulmonary disease in the AUI group, with increased frequency of postoperative complications and longer hospital stays. Despite this, at 30 days and 1 year, the incidence of reintervention and all-cause mortality was equivalent between the two groups.


Conclusion


The global success of EVAR following its initial incarnation cannot be overestimated. The AUI technique paved the way for successful treatment of a cohort previously considered inoperable. However, with the development and continued improvements of bifurcated devices, along with increasing endovascular skills, AUI has fallen from favor. This largely relates to the need for a crossover grafts rather than concerns about the AUI device in isolation. Although AUI has evolved into the variety of bifurcated grafts now available, it still plays a significant role in the treatment of anatomically challenging AAA and for patients requiring speedy aneurysm exclusion. Its use in rAAA has been successfully explored and championed by the European vascular surgery community. Many still maintain a stock AUI on the shelf, available as part of their endovascular armamentarium.


Physician-Modified Endovascular Grafts for Treating Ruptured Abdominal Aortic Aneurysms



Benjamin W. Starnes21  


(21)
Division of Vascular Surgery, Department of Surgery, University of Washington, Regional Vascular Center at Harborview Medical Center, 325 9th Ave, Box 359908, Seattle, WA 98104, USA

 



 

Benjamin W. Starnes



Key Points





  • Physician-modified endovascular grafts have been successfully used to treat patients presenting with rAAA who are not candidates for standard EVAR.


  • These procedures are off-label in nature and require the umbrella of an FDA-approved investigational device exemption (IDE) clinical trial in order to be reimbursed.


  • These grafts may be manufactured prior to the arrival of the patient from the transferring facility.


Introduction


The purpose of this chapter is to introduce the concept of custom fenestrated EVAR for managing ruptured abdominal aortic aneurysms (rAAA). Fenestrated endovascular repair was first performed in 1999 by the late John L. Anderson of Adelaide, Australia, and involves the preoperative placement of “fenestra” or windows, in precise locations on an endograft in order to treat juxtarenal AAA [88]. Currently in the United States, there is only one manufacturer of an FDA-approved fenestrated endograft, and these custom-designed grafts require a minimum of 4 weeks to arrive at the implanting facility after the graft has been meticulously planned and the order has been placed. Thus, many believe that custom-designed devices cannot be used in a rupture situation. We will demonstrate that this is not true.

Vascular surgeons have long been known to innovate to meet the needs of their patients. At the University of Washington, we initiated a protocol for managing rAAA with an endovascular first strategy in 2007 and reduced our 30-day mortality from 58 to 32 % overall with those patients harboring anatomy suitable for EVAR experiencing an 18 % mortality risk at 30 days [89]. We quickly learned that reasons for ineligibility for EVAR revolved around inadequate, often short, infrarenal aortic necks. We thus began customizing our own devices in an off-label fashion to create single, double, and even triple fenestration endografts to treat this subset of patients who could not wait the lengthy duration to receive the custom-made graft and/or were too sick to undergo open repair [90, 91]. In this chapter, we describe the technique of physician-modified endografting to treat asymptomatic, symptomatic, or even ruptured AAA.


Technique



Device Preparation


All operative procedures are performed concurrently with back table device modification while the patient is being prepared for surgery. In urgent situations, temporary aortic balloon occlusion can be performed to bide time, especially with single and double fenestration cases where graft manufacture time is less than 30 min. The device is chosen according to standard instructions for use in sizing guidelines, and a routine aortic oversizing of 10–15 % for the main body graft is utilized. The bifurcated graft is unsheathed on a separate table, and a sterile marking pen is used to mark the location of the fenestrations based on both length and clock face and arc-length measurements that had been previously determined with reconstruction imaging software. Minor adjustments are made in localization of the fenestrations to allow for maximum usage of strut-free fenestrations when possible. When this is not possible and multiple fenestrations are required, struts within fenestrations are preferentially avoided for the renal arteries. An ophthalmic Bovie cautery device (Medtronic, Minneapolis, Minn) is used to carefully burn the Dacron fabric to create all fenestrations and thus avoid fabric fraying and allow for heat sealing. Gold, 15-mm Amplatz Gooseneck Snares (EV3 Endovascular Inc., Plymouth, Minn) are then used to reinforce all fenestrations. These are handsewn into place using 4-0 Prolene suture in a 720° running fashion (Fig. 13.19). A typical final PMEG device is depicted in Fig. 13.20.

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Fig. 13.19
Gold, 15-mm Amplatz Gooseneck Snares (EV3, Plymouth, Minn) were then used to reinforce all fenestrations. These were handsewn into place using 4-0 Prolene suture in a 720° running fashion


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Fig. 13.20
A typical physician-modified endovascular graft (PMEG) prior to device repackaging (a). Fenestrations for the superior mesenteric artery (SMA) (struts present) and left and right renal arteries (strutfree) were created for this particular patient. (b) Rerouting of the trigger wire to allow for placement of graft constraining ties

When time permits, diameter-reducing ties are then used to constrain the device along its posterior border (opposite the superior mesenteric artery [SMA] and/or celiac fenestration at 6 o’clock) by rerouting the existing proximal trigger wire through and through the graft material at the midportion of each of the top two Z stents. This is facilitated using a micropuncture needle from inside the graft. The constraining ties are then tied down into place over the trigger wire. The bare stent is then reconstrained in the top cap, and the entire graft wetted with heparinized saline and then reloaded into the existing sheath.


PMEG Procedural Details


The majority of these procedures are performed in a modern hybrid operating room utilizing a Siemens Artis Q Zeego System (Siemens, Munich, Germany). Common femoral access is almost always achieved in a standard percutaneous fashion and the stent graft delivered up into position near the visceral vessels. A contrast aortogram with 20 mL of dilute contrast injected at 10 mL/s is performed with the PMEG in place to mark the visceral vessels (Fig. 13.21). Proper orientation of the graft (SMA anterior) is confirmed by rotating the graft clockwise under fluoroscopy and confirming that the SMA fenestration moves from left to right instead of right to left, which would denote a posterior orientation of the SMA fenestration (Fig. 13.22). The graft is then carefully deployed down to the opening of the contralateral limb. The contralateral limb is then selected, and, typically, an 18–20 Fr DrySeal sheath (W.L. Gore, Flagstaff, AZ) is inserted into the contralateral limb over a stiff wire under direct fluoroscopic visualization. It is important to hub the DrySeal sheath to create a stable working platform. Double 6 or 7 Fr Ansel sheaths (Cook Inc.) are used directly through the end of the DrySeal sheath to individually select the renal arteries while maintaining stability of the PMEG device. Once the renal arteries are completely selected with each 6 or 7 Fr sheath, diameter-reducing ties are freed by pulling the proximal trigger wire out, and then the top cap is released and the main body deployed. At this time, the remainder of the main body device is deployed, the top cap is retrieved, and a CODA balloon (Cook Inc.) is used to seat the proximal portion of the graft in the zone of the visceral aortic stent graft segment (Fig. 13.23). The renal arteries are then individually stented with appropriately sized iCAST stents (Atrium USA, Hudson, NH), and the stents are flared proximally into the aortic stent graft using 9–12 mm standard angioplasty balloons (Fig. 13.24). The remainder of the procedure involves standard placement of docking limbs to the level of each iliac bifurcation and seating of the stent graft overlap and seal zones with a molding balloon (CODA, Cook Inc.). A completion aortogram is performed at the completion of each procedure (Fig. 13.25).

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Fig. 13.21
Contrast aortography and cartoon demonstrating the origins of all four visceral vessels with the physician-modified endovascular graft (PMEG) device in situ prior to and after deployment


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Fig. 13.22
Proper orientation of the graft is confirmed by rotation of the graft clockwise and viewing the SMA fenestration move from left to right on the screen


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Fig. 13.23
Physician-modified endovascular graft (PMEG) procedure. (a) Both renal arteries have been selected through the renal fenestrations and a sheath advanced into the left renal artery. (b) Seating of the proximal graft with the renal sheaths securely in place. (c) Stent grafting and subsequent flaring of the renal artery stents


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Fig. 13.24
Flaring of the renal stents with appropriately oversized balloons


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Fig. 13.25
Completion aortogram and cartoon demonstrating absence of endoleak and good alignment of all three visceral vessel fenestrations

Other devices from other manufacturers have been successfully modified to include Medtronic Endurant (Medtronic, Minneapolis, MN), Bolton Relay (Bolton, Sunrise, FL), and Gore Excluder (W.L. Gore, Flagstaff, AZ). It is important to know how to successfully reload each of these devices prior to embarking on a surgeon-modified repair of a ruptured abdominal aortic aneurysm.


Conclusions


Custom-designed and manufactured devices can be used to successfully repair ruptured abdominal aortic aneurysms. In the future, more patients harboring ruptured abdominal aortic aneurysms will benefit from technological improvements and a “kit” type of off-the-shelf tools and devices to personalize therapy for each patient.


Endovascular Aneurysm Sealing for Ruptured Abdominal Aortic Aneurysm



Andrew Holden22  


(22)
Department of Interventional Radiology, Auckland Hospital, Auckland, New Zealand

 



 

Andrew Holden



Key Points



Nov 11, 2017 | Posted by in ABDOMINAL MEDICINE | Comments Off on Operative Strategies
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