Although conventional manometry set the basis for the diagnosis of esophageal motility disorders, the large axial spacing between recording sites leaves large portions of the esophagus unevaluated and vulnerable to movement artifact. However, continuous spatiotemporal representations of pressure through the esophagus recorded with high-resolution manometry offers greater detail and improved accuracy for many of the most important measurements of esophageal motor function. This review describes how the new classification schemes for esophageal pressure topography have evolved from conventional criteria and focuses on how esophageal pressure topography has improved the ability to subcategorize conventional manometric diagnoses into new functional phenotypes.
Key points
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Diagnostic schemes for conventional manometry and esophageal pressure topography (EPT) rely on measurements of key variables and descriptions of patterns of contractile activity. However, the enhanced assessment of esophageal motility and sphincter function available with EPT has led to the further characterization of clinically relevant phenotypes.
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Differentiation of achalasia into subtypes provides a method to predict the response to treatment.
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A diagnosis of diffuse esophageal spasm represents a unique clinical phenotype when defined by premature esophageal contraction (measured via distal latency) instead of when defined by rapid contraction (measured by contractile front velocity and/or wave progression) alone.
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Defining hypercontractile esophagus with a single swallow with a significantly elevated distal contractile integral, as opposed to using a mean value more than a predetermined 95th percentile, may define a more specific clinical syndrome characterized by chest pain and/or dysphagia.
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EPT correlates of the conventional manometric diagnosis of ineffective esophageal motility include weak and frequent-failed peristalsis; however, the clinical significance of these diagnoses is not completely understood.
Introduction
In 2001, based on a review of the literature to date, Spechler and Castell proposed a classification scheme for esophageal motility disorders incorporating defined conventional manometry (CM) criteria. This description was the state-of-the-art description of manometry at the time. However, the investigators recognized that the clinical significance of any observed manometric findings may be limited because the abnormalities were often reported to occur with poor correlation to symptoms, and therapeutic corrections of manometric findings often did not lead to improvement in symptoms.
A few years after that review, high-resolution manometry (HRM) and esophageal pressure topography (EPT) started to appear on the scene, both in research and clinical practice. HRM is comprised of multiple, closely spaced pressure sensors (usually 1 cm apart) that record pressure without significant gaps in data along the length of the esophagus. This data can be modified using interpolation to generate EPT plots that are color coded, spatiotemporal representations of pressure recordings in the esophagus (Clouse plots). This technology lends itself to an objective assessment of EPT metrics that have been integrated into a new classification scheme for esophageal motility disorders, referred to as the Chicago classification scheme. As clinical and research experience grows with HRM, the Chicago classification scheme has been intermittently updated in an attempt to improve its representation of clinically relevant phenotypes. The goal of this review is to compare conventional and HRM classification schemes for esophageal motility disorders and to illustrate how these new clinical phenotypes on EPT have evolved from previous definitions used by Spechler and Castell for CM.
Introduction
In 2001, based on a review of the literature to date, Spechler and Castell proposed a classification scheme for esophageal motility disorders incorporating defined conventional manometry (CM) criteria. This description was the state-of-the-art description of manometry at the time. However, the investigators recognized that the clinical significance of any observed manometric findings may be limited because the abnormalities were often reported to occur with poor correlation to symptoms, and therapeutic corrections of manometric findings often did not lead to improvement in symptoms.
A few years after that review, high-resolution manometry (HRM) and esophageal pressure topography (EPT) started to appear on the scene, both in research and clinical practice. HRM is comprised of multiple, closely spaced pressure sensors (usually 1 cm apart) that record pressure without significant gaps in data along the length of the esophagus. This data can be modified using interpolation to generate EPT plots that are color coded, spatiotemporal representations of pressure recordings in the esophagus (Clouse plots). This technology lends itself to an objective assessment of EPT metrics that have been integrated into a new classification scheme for esophageal motility disorders, referred to as the Chicago classification scheme. As clinical and research experience grows with HRM, the Chicago classification scheme has been intermittently updated in an attempt to improve its representation of clinically relevant phenotypes. The goal of this review is to compare conventional and HRM classification schemes for esophageal motility disorders and to illustrate how these new clinical phenotypes on EPT have evolved from previous definitions used by Spechler and Castell for CM.
Methodology: CM and HRM
The procedure for both types of manometry begins with the placement of the manometry catheter transnasally until the distal pressure sensors cross the esophagogastric junction (EGJ) and enter the stomach. The comparative measurements made with CM and HRM are displayed in Table 1 .
| Esophageal Motility Characteristic | CM Measurement | HRM Measurement |
|---|---|---|
| LES relaxation | ||
| LES relaxation with swallow | IRP | |
| Normal a | Complete (<8 mm Hg more than gastric pressure) | <15 mm Hg |
| Peristaltic propagation | ||
| Wave progression between pressure sensors 8 and 3 cm above the LES | CFV | |
| Normal a | 2–8 cm/s (UES to LES) | <9 cm/s |
| (no corresponding CM metric) | DL | |
| Normal a | ≥4.5 s | |
| Contractile vigor | ||
| Mean distal wave maximum amplitude of pressure sensors 8 and 3 cm above the LES | DCI | |
| Normal a | 30–180 mm Hg | 450–5000 mmHg-s-cm |
In CM, a pull-through technique is used to determine the position of the lower esophageal sphincter (LES) pressure by identifying the pressure inversion point and a high-pressure zone. The pressure sensor is then left positioned in the LES, and the basal pressure is recorded over at least 2 minutes with minimal swallowing. Once the baseline recording is complete, LES relaxation is measured during at least 5 wet (5 mL water) swallows with the pressure sensor maintained at the position where the middle of the LES high-pressure zone was recorded. Peristaltic function is typically assessed with pressure sensors spaced anywhere from 3 to 5 cm apart, with a repositioning of the pressure sensors into the body or by simultaneous pressure recording at the LES using a sleeve or single sensor.
In HRM, the distal end of the catheter is passed into the gastric compartment below the LES and hiatal canal, and no pull through is required because the catheter can provide recording from the stomach through the esophagus into the oropharynx. During an HRM study, EPT plots, also known as Clouse plots, are generated by computer software during 10 wet (5 mL water) swallows, and there is no need to perform different steps in the evaluation because all variables can be assessed during the single swallows.
Analysis of an EPT study is performed using a stepwise approach that focuses on an algorithm-based scheme that first defines patients based on EGJ relaxation pressures and subsequently uses individual swallow patterns defined by EPT metrics to further subclassify patients into specific categories.
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Step 1: Assessment of EGJ pressure morphology at baseline
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The first step of the analysis process focuses on describing the pressure morphology of the EGJ to determine whether a hiatus hernia is present and where the pressure inversion point is located because this can have dramatic effects on the measures of EGJ function. The baseline end-expiratory pressure and inspiratory augmentation are recorded to assess the integrity of the crural diaphragm as an extrinsic sphincter.
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Step 2: Assessing EGJ relaxation and bolus pressure dynamics through the EGJ
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Patients are defined as having normal or abnormal EGJ relaxation using the integrated relaxation pressure (IRP). The IRP is the lowest mean EGJ pressure for 4 contiguous or noncontiguous seconds during the deglutitive period. As demonstrated in Fig. 1 , the IRP has replaced the conventional measures of nadir or end-expiratory LES relaxation pressure on CM because EPT evaluation made it quite clear that the pressure measured through the EGJ during swallowing was heavily reliant on intrabolus pressure and was not a pure measure of LES relaxation.
Fig. 1
Assessment of EGJ relaxation. Nadir LES pressure (CM line tracing, purple ) and IRP ( dotted white boxes indicating lowest LES pressure segments over 4 noncontiguous seconds) are demonstrated in a normal swallow. IRP 4.8 mm Hg. Nadir LES pressure 0.3 mm Hg more than gastric pressure. The nadir pressure is likely a measurement of intragastric pressure.
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Step 3: Assess integrity of the peristaltic wave
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Once the IRP is measured, esophageal peristaltic integrity is characterized to determine if the peristaltic activity is intact, failed, or associated with small (2–5 cm) or large (>5 cm) peristaltic breaks in the 20-mm Hg isobaric contour. This step is performed before any other measurements are made because the subsequent measurements depend on the presence of intact or preserved peristaltic integrity in the distal esophagus. This metric is similar to using a 30-mm Hg threshold at 3 and 8 cm above the proximal border of the LES to define effective swallows. However, the isobaric contour tool provides a more complete assessment of the swallow as demonstrated in Fig. 2 .
Fig. 2
Peristaltic integrity. A Clouse plot of a swallow with a large (5.1 cm axial length) peristaltic defect in the 20-mm Hg isobaric contour is displayed. CM line tracings at 3 and 8 cm would not normally detect this defect in the transition zone. Black lines indicate the CM recording sites with their position from the LES (eg, 3 cm, as labeled).
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Step 4: Determine the location of the contractile deceleration point (CDP)
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The CDP is defined as the inflection point along the contractile wavefront defined by the 30-mm Hg isobaric contour tool where the greatest deceleration occurs and the function of the esophagus converts from a stripping wave to a compartmentalized ampulla to promote emptying of the remaining bolus ( Fig. 3 ). This landmark is in close proximity to the proximal border of the LES during maximal shortening and is usually associated with maximal concurrent axial contraction of the esophageal body. The CDP should be localized within the third contractile segment defined by Clouse, and there is no method or measure on CM that localizes the CDP.
Fig. 3
Propagation of peristalsis. The EPT metrics of CDP, distal latency (DL), contractile front velocity (CFV), and the CM wavefront progression are displayed on a normal swallow. The CDP ( red circle ) is located at the intersection of the CFV tangent ( white dashed line ) and the velocity tangent of the terminal segment of esophageal peristalsis ( solid white line ), which correlates with emptying of the esophageal ampulla. The DL ( purple arrow ) is defined as the time from the initiation of the swallow to the CDP and measures 7 seconds in the swallow. The wavefront progression ( black dashed line ) is determined from CM line tracings (measuring 5.0 cm/s) and is comparable to the CFV (3.4 cm/s) in EPT.
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Step 5: Assess propagation
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Propagation and timing of peristalsis is defined by assessing the distal latency to determine whether the swallow is premature and possibly associated with impaired inhibitory function of the esophageal body. It is defined as the interval between upper esophageal relaxation and the CDP, as demonstrated in Fig. 3 . There is no correlate to this metric in CM.
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Velocity of the stripping wave is determined by an assessment of the contractile front velocity (CFV). It is defined as the slope of the tangent approximating the 30-mm Hg isobaric contour between the proximal pressure trough and the contractile deceleration point. This measurement is akin to the measurement of velocity using the pressure sensor located 3 and 8 cm above the proximal aspect of the LES on CM. It is interesting that the 3-cm point used on CM closely approximates the CDP; thus, this measure has good correlation with CFV.
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Step 6: Measure contractile vigor
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Contractile vigor has been revised to objectively measure all of the contractile activity within the domain of the distal smooth muscle esophagus below the transition zone. The transition zone is typically localized approximately 6 cm below the lower border of the Upper esophageal sphincter (UES) and represents the first pressure trough between segments 1 and 2 on the Clouse plot. The metric used to quantify the contractile activity between the transition zone and proximal aspect of the EGJ is termed the distal contractile integral (DCI), and it uses the space time domain of the second and third contractile segments to provide a single number that quantifies contractile vigor ( Fig. 4 ). The DCI is used in place of measuring the mean value of the highest wave amplitude at 3 and 8 cm above the proximal aspect of the LES on CM. The EPT plots also allow a qualitative assessment of the contraction that helps define focal contractile abnormalities and disorders associated with LES after contraction.
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