The OverStitch Endoscopic Suturing System is composed of an end cap, a needle driver handle, and an anchor exchange catheter (Fig. 7.4a). The distal tip of the endoscope is attached to the end cap, which has a hinged, curved, hollow needle body that opens and closes in an arc (Fig. 7.4b). The needle driver handle opens and closes the suture arm. The suture cassette contains a suture that is attached to a tissue anchor, which acts as the tip of the suturing needle, and attaches to the suture arm. After a suture is positioned through tissue, the anchor exchange catheter allows the tip of the needle to retract and pierce additional tissue [2] (VIDEO 1).

One advantage of this suturing method is that it allows continuous or interrupted stitches to be made of various lengths [13, 20]. The endoscope does not need to be removed from the lumen for reloading needles or cinching. Furthermore, each stitch is finished with intracorporeal knot tying with a uniquely designed cinching device [20]. Since the technique is not suction based, the depth of tissue needle penetration can accurately be predicted [12].

The Amplatzer Septal Occluder is a dumbbell-shaped device composed of 2 self-expandable, umbrella-shaped disks made of nitinol mesh with polyester fabric that are constrained within a 70-cm delivery catheter and deployed over an endoscopically placed guidewire [14, 16]. The occluder is a US Food and Drug Administration-approved device for the closure of atrial septal defects [14]. The polyester fabric is sewn securely to each disk to help close the hole and serve as a foundation for growth of tissue over the occluder after placement [15, 16]. The device also possesses radiopaque marker bands that can be used under fluoroscopy [16]. Although the delivery catheter is too short to be passed through an endoscope, a guidewire can be inserted under endoscopic guidance. When the endoscope is withdrawn, the occluder can be reintroduced on the guidewire [16]. The device apposes the wall on each side of the defect, thus occluding it and creating a platform for subsequent tissue ingrowth and epithelialization [16]. These devices can be found in a variety of waist diameters and lengths depending on the defect that needs closure [2].

Some instruments are available to facilitate the use of the OTSC including reloaders, twin graspers, and anchors. Reloaders allow for mounting of additional clips onto the applicator cap after the initial clip is deployed and can be used if more than one clip is to be placed during the same phase of the procedure [2]. The twin grasper is useful for large defects and chronic defects associated with induration in light of its ability to facilitate tissue apposition before clip deployment. The anchors are used to retract fibrotic tissue into the cap. Anchors consist of a long catheter with 3 retractable needle pins that pierce the tissue when deployed to anchor the tissue. Subsequently, the tissue can be pulled into the applicator cap and the clip can be deployed [2].

The key element to technical success is the positioning of the lesion within the OTSC cap [1]. Misfiring to one side of a lesion can affect successful deployment of a second clip over the defect.

Clips such as the OTSC are more difficult to apply in cases of larger defects because of an inability to accomplish deep-tissue capture due to low closure force and restricted opening distance between the jaws of the clip [2]. Furthermore, in cases where the tissue is inflamed, indurated, and fibrotic such as the case of chronic fistulas, endoscopic clips are particularly troublesome and may result in challenging and protracted procedures, failure of adequate tissue apposition, and inability to properly deploy the OTSC [1, 2].