Assessment of esophageal body peristaltic work using functional lumen imaging probe panometry

Automatic three-dimensional reconstruction of the oesophagus in achalasia patients undergoing POEM: an innovative approach for evaluating treatment outcomes

BACKGROUND AND AIMS

Peroral endoscopic myotomy (POEM) is a standard treatment option for achalasia patients. Treatment response varies due to factors such as achalasia type, degree of dilatation, pressure and distensibility indices. We present an innovative approach for treatment response prediction based on an automatic three-dimensional (3-D) reconstruction of the tubular oesophagus (TE) and the lower oesophageal sphincter (LES) in patients undergoing POEM for achalasia.

METHODS

A software was developed, integrating data from high-resolution manometry, timed barium oesophagogram and endoscopic images to automatically generate 3-D reconstructions of the TE and LES. Novel normative indices for TE (volume×pressure) and LES (volume/pressure) were automatically integrated, facilitating pre-POEM and post-POEM comparisons. Treatment response was evaluated by changes in volumetric and pressure indices for the TE and the LES before as well as 3 and 12 months after POEM. In addition, these values were compared with normal value indices of non-achalasia patients.

RESULTS

50 treatment-naive achalasia patients were enrolled prospectively. The mean TE index decreased significantly (p<0.0001) and the mean LES index increased significantly 3 months post-POEM (p<0.0001). In the 12-month follow-up, no further significant change of value indices between 3 and 12 months post-POEM was seen. 3 months post-POEM mean LES index approached the mean LES of the healthy control group (p=0.077).

CONCLUSION

3-D reconstruction provides an interactive, dynamic visualisation of the oesophagus, serving as a comprehensive tool for evaluating treatment response. It may contribute to refining our approach to achalasia treatment and optimising treatment outcomes.

TRIAL REGISTRATION NUMBER

22-0149.

Assessing mechanical function of peristalsis with functional lumen imaging probe panometry: Contraction power and displaced volume

BACKGROUND AND AIMS

The distal contractile integral (DCI) quantifies the contractile vigor of primary peristalsis on high-resolution manometry (HRM), whereas no such metric exists for secondary peristalsis on functional lumen imaging probe (FLIP) panometry. This study aimed to evaluate novel FLIP metrics of contraction power and displaced volume in asymptomatic controls and a patient cohort.

METHODS

Thirty-five asymptomatic controls and adult patients (with normal esophagogastric junction outflow/opening and without spasm) who completed HRM and FLIP panometry were included. The patient group also completed timed barium esophagram (TBE). Contraction power (estimate of esophageal work over time) and displaced volume (estimate of contraction-associated fluid flow) were computed from FLIP. HRM was analyzed per Chicago Classification v4.0.

KEY RESULTS

In controls, median (5th-95th percentile) contraction power was 27 mW (10-44) and displaced volume was 43 mL (17-66). 95 patients were included: 72% with normal motility on HRM, 17% with ineffective esophageal motility (IEM), and 12% with absent contractility. Among patients, DCI was significantly correlated with both contraction power (rho = 0.499) and displaced volume (rho = 0.342); p values < 0.001. Both contraction power and displaced volume were greater in patients with normal motility versus IEM or absent contractility, complete versus incomplete bolus transit, and normal versus abnormal retention on TBE; p values < 0.02.

CONCLUSIONS

FLIP panometry metrics of contraction power and displaced volume appeared to effectively quantify peristaltic vigor. These novel metrics may enhance evaluation of esophageal motility with FLIP panometry and provide a reliable surrogate to DCI on HRM.

Endoluminal Procedures and Devices for Esophageal Tract Investigation: A Critical Review

Diseases of the esophageal tract represent a heterogeneous class of pathological conditions for which diagnostic paradigms continue to emerge. In the last few decades, innovative diagnostic devices have been developed, and several attempts have been made to advance and standardize diagnostic algorithms to be compliant with medical procedures. To the best of our knowledge, a comprehensive review of the procedures and available technologies to investigate the esophageal tract was missing in the literature. Therefore, the proposed review aims to provide a comprehensive analysis of available endoluminal technologies and procedures to investigate esophagus health conditions. The proposed systematic review was performed using PubMed, Scopus, and Web of Science databases. Studies have been divided into categories based on the type of evaluation and measurement that the investigated technology provides. In detail, three main categories have been identified, i.e., endoluminal technologies for the (i) morphological, (ii) bio-mechanical, and (iii) electro-chemical evaluation of the esophagus.

A mechanics-based perspective on the function of the esophagogastric junction during functional luminal imaging probe manometry

The esophagogastric junction (EGJ) is located at the distal end of the esophagus and acts as a valve allowing swallowed food to enter the stomach and preventing acid reflux. Irregular weakening or stiffening of the EGJ muscles results in changes to its opening and closing patterns which can progress into esophageal disorders. Therefore, understanding the physics of the opening and closing cycle of the EGJ can provide mechanistic insights into its function and can help identify the underlying conditions that cause its dysfunction. Using clinical functional lumen imaging probe (FLIP) data, we plotted the pressure-cross-sectional area loops at the EGJ location and distinguished two major loop types-a pressure dominant loop and a tone dominant loop. In this study, we aimed to identify the key characteristics that define each loop type and determine what causes the inversion from one loop to another. To do so, the clinical observations are reproduced using 1D simulations of flow inside a FLIP device located in the esophagus, and the work done by the EGJ wall over time is calculated. This work is decomposed into active and passive components, which reveal the competing mechanisms that dictate the loop type. These mechanisms are esophageal stiffness, fluid viscosity, and the EGJ relaxation pattern.

Peristaltic regimes in esophageal transport

A FLIP device gives cross-sectional area along the length of the esophagus and one pressure measurement, both as a function of time. Deducing mechanical properties of the esophagus including wall material properties, contraction strength, and wall relaxation from these data are a challenging inverse problem. Knowing mechanical properties can change how clinical decisions are made because of its potential for in-vivo mechanistic insights. To obtain such information, we conducted a parametric study to identify peristaltic regimes by using a 1D model of peristaltic flow through an elastic tube closed on both ends and also applied it to interpret clinical data. The results gave insightful information about the effect of tube stiffness, fluid/bolus density and contraction strength on the resulting esophagus shape through quantitive representations of the peristaltic regimes. Our analysis also revealed the mechanics of the opening of the contraction area as a function of bolus flow resistance. Lastly, we concluded that peristaltic driven flow displays three modes of peristaltic geometries, but all physiologically relevant flows fall into two peristaltic regimes characterized by a tight contraction.

A mechanics-based perspective on the pressure-cross-sectional area loop within the esophageal body

Introduction: Plotting the pressure-cross-sectional area (P-CSA) hysteresis loops within the esophagus during a contraction cycle can provide mechanistic insights into esophageal motor function. Pressure and cross-sectional area during secondary peristalsis can be obtained from the functional lumen imaging probe (FLIP). The pressure-cross-sectional area plots at a location within the esophageal body (but away from the sphincter) reveal a horizontal loop shape. The horizontal loop shape has phases that appear similar to those in cardiovascular analyses, whichinclude isometric and isotonic contractions followed by isometric and isotonic relaxations. The aim of this study is to explain the various phases of the pressurecross-sectional area hysteresis loops within the esophageal body. Materials and Methods: We simulate flow inside a FLIP device placed inside the esophagus lumen. We focus on three scenarios: long functional lumen imaging probe bag placed insidethe esophagus but not passing through the lower esophageal sphincter, long functional lumen imaging probe bag that crosses the lower esophageal sphincter, and a short functional lumen imaging probe bag placed in the esophagus body that does not pass through the lower esophageal sphincter. Results and Discussion: Horizontal P-CSA area loop pattern is robust and is reproduced in all three cases with only small differences. The results indicate that the horizontal loop pattern is primarily a product of mechanical conditions rather than any inherently different function of the muscle itself. Thus, the distinct phases of the loop can be explained solely based on mechanics.

Estimation of mechanical work done to open the esophagogastric junction using functional lumen imaging probe panometry

In this study, we quantify the work done by the esophagus to open the esophagogastric junction (EGJ) and create a passage for bolus flow into the stomach. Work done on the EGJ was computed using functional lumen imaging probe (FLIP) panometry. Eighty-five individuals underwent FLIP panometry with a 16-cm catheter during sedated endoscopy including asymptomatic controls (n = 14), 45 patients with achalasia (n = 15 each, three subtypes), those with gastroesophageal reflux disease (GERD; n = 13), those with eosinophilic esophagitis (EoE; n = 8), and those with systemic sclerosis (SSc; n = 5). Luminal cross-sectional area (CSA) and pressure were measured by the FLIP catheter positioned across the EGJ. Work done on the EGJ (EGJW) was computed (millijoules, mJ) at 40-mL distension. Additionally, a separate method was developed to estimate the "work required" to fully open the EGJ (EGJROW) when it did not open during the procedure. EGJW for controls had a median [interquartile range (IQR)] value of 75 (56-141) mJ. All achalasia subtypes showed low EGJW compared with controls (P < 0.001). Subjects with GERD and EoE had EGJW 54.1 (6.9-96.3) and 65.9 (10.8-102.3) mJ, similar to controls (P < 0.08 and P < 0.4, respectively). The scleroderma group showed low values of EGJW, 12 mJ (P < 0.001). For patients with achalasia, EGJROW was the greatest and had a value of 210.4 (115.2-375.4) mJ. Disease groups with minimal or absent EGJ opening showed low values of EGJW. For patients with achalasia, EGJROW significantly exceeded EGJW values of all other groups, highlighting its unique pathophysiology. Balancing the relationship between EGJW and EGJROW is potentially useful for calibrating achalasia treatments and evaluating treatment response.NEW & NOTEWORTHY Changes in pressure and diameter occur at the EGJ during esophageal emptying. Similar changes can be observed during FLIP panometry. Data from healthy and diseased individuals were used to estimate the mechanical work done on the EGJ during distension-induced relaxation or, in instances of failed opening, work required to open the EGJ. Quantifying these parameters is potentially valuable to calibrate treatments and gauge treatment efficacy for subjects with disorders of EGJ function, especially achalasia.

[Diagnosis of Dysphagia: High Resolution Manometry & EndoFLIP]

Esophageal motility disorders were re-defined when high-resolution manometry was employed to better understand their pathogenesis. Newly developed parameters including integrated relaxation pressure (IRP), distal contractile integral, and distal latency showed better diagnostic yield compared with previously used conventional parameters. Therefore, Chicago classification was formulated, and its diagnostic cascade begins by assessing the IRP value. However, IRP showed limitation due to its inconsistency, and other studies have tried to overcome this. Recent studies showed that provocative tests, supplementing the conventional esophageal manometry protocol, have improved the diagnostic yield of the esophageal motility disorders. Therefore, position change from supine to upright, solid or semi-solid swallowing, multiple rapid swallows, and the rapid drink challenge were newly added to the manometry protocol in the revised Chicago classification version 4.0. Impedance planimetry enables measurement of bag cross-sectional area at various locations. The functional lumen imaging probe (FLIP) has been applied to assess luminal distensibility. This probe can also measure pressure, serial cross-sectional areas, and tension-strain relationship. The esophagogastric junction's distensibility is decreased in achalasia. Therefore, EndoFLIP can be used to assess contractility and distensibility of the esophagus in the patients with achalasia, including repetitive antegrade or retrograde contractions. EndoFLIP can detect achalasia patients with relatively low IRP, which was difficult to diagnose using the current high-resolution manometry. EndoFLIP also provides information on the contractile activity and distensibility of the esophageal body in patients with achalasia. The use of provocative tests, newly added in Chicago classification 4.0 version, and EndoFLIP can expand understanding of esophageal motility disorders.