The rhythm and rate of distension-induced esophageal contractility: A physiomarker of esophageal function

A Standardized Approach to Performing and Interpreting Functional Lumen Imaging Probe Panometry for Esophageal Motility Disorders: The Dallas Consensus

BACKGROUND & AIMS

Functional lumen imaging probe (FLIP) panometry provides assessment of the esophagogastric junction opening and esophageal body contractile activity during an endoscopic procedure and is increasingly being incorporated into comprehensive esophageal motility assessments. The aim of this study was to provide a standardized approach and vocabulary to the procedure and interpretation and update the motility classification scheme.

METHODS

A working group of 19 FLIP panometry experts convened in a modified Delphi consensus process to produce and assess statements on the FLIP panometry procedure and interpretation. Three rounds of voting were conducted on an agreement scale of 1-9 for appropriateness, followed by face-to-face discussions and an opportunity for revisions of statements. The "percent agreement" was the proportion of votes with score ≥7 indicating level of agreement on appropriateness.

RESULTS

A total of 40 statements were selected for final inclusion in the Dallas Consensus, including FLIP panometry protocol, interpretation of esophagogastric junction opening and contractile response, and motility classification scheme. Key statements included: "FLIP panometry should be interpreted in the context of the clinical presentation, the accompanying EGD [esophagogastroduodenoscopy] findings and other relevant complementary testing" (median response 9.0; 100% agreement). "A major motor disorder is unlikely in the setting of a 'normal' FLIP panometry classification" (median response 9.0; 94% agreement). "Diminished or absent contractile response with reduced esophageal opening (ie, nonspastic obstruction) supports the diagnosis of a disorder of EGJ [esophagogastric junction] outflow" (median response 8.5; 94% agreement).

CONCLUSIONS

The standardized approach for performance and interpretation of the Dallas Consensus can facilitate use of FLIP panometry in broad clinical settings.

Direct and Retrograde Wave Propagation in Unidirectionally Coupled Wilson-Cowan Oscillators

Some biological systems exhibit both direct and retrograde propagating signal waves despite unidirectional coupling. To explain this phenomenon, we study a chain of unidirectionally coupled Wilson-Cowan oscillators. Surprisingly, we find that changes in the homogeneous global input to the chain suffice to reverse the wave propagation direction. To obtain insights, we analyze the frequencies and bifurcations of the limit cycle solutions of the chain as a function of the global input. Specifically, we determine that the directionality of wave propagation is controlled by differences in the intrinsic frequencies of oscillators caused by the differential proximity of the oscillators to a homoclinic bifurcation.

Disorders of secondary peristalsis are associated with the development of esophagitis

BACKGROUND

Disorders of primary peristalsis are associated with a higher percent time pH <4 in the esophagus suggesting poor acid clearance. However, there are no studies of secondary peristalsis and its relationship to microscopic or erosive esophagitis. The goal of this study was to determine the relationship between secondary peristalsis using functional luminal imaging probes (EndoFLIP) and the presence or absence of esophagitis.

METHODS

We reviewed the endoscopic and EndoFLIP 2.0 tracings for 103 consecutive patients including those with a history of upper gastrointestinal surgery undergoing upper endoscopy. Esophagogastric junction (EGJ) distensibility and diameter, repetitive antegrade contraction (RACs) presence and frequency, and occlusive diameters were measured. Measurements were then compared between patients with and without microscopic and/or erosive esophagitis. Means were compared using t-tests. Proportions were compared using Chi-Squared analyses.

KEY RESULTS

One hundred and three patients were included (mean age: 14.4 + 6.4 years). Ten patients had erosive esophagitis and 28 patients had microscopic esophagitis. Erosive and microscopic esophagitis were associated with abnormal or absent of RACs (p < 0.001). Occlusive diameters were higher in patients with esophagitis compared to those without (p < 0.001). There was no relationship between EGJ distensibility and the presence of erosive or microscopic esophagitis (p = 0.4). The absence of RACs was the only independent predictor of esophagitis (erosive and microscopic), after controlling for age, proton pump inhibitors (PPI) use and EGJ distensibility (p < 0.001).

CONCLUSIONS & INFERENCES

Abnormal secondary peristalsis is associated with microscopic and gross esophagitis, suggesting that EndoFLIP should be part of the diagnostic algorithm for esophagitis.

Age Affects Esophageal Secondary Peristalsis More Than Primary as Assessed by FLIP Panometry and High-resolution Manometry

Age-related changes in esophageal function involve increased rates of dysmotility with advancing age (sometimes described as presbyesophagus).1-4 Specifically, advanced age has been associated with increased lower esophageal sphincter (LES) pressure and decreased peristaltic vigor.1-4 However, the mechanisms underlying these changes, including the relative relationship of primary peristalsis and secondary peristalsis over the lifespan, remain incompletely understood. Current approaches assess primary peristalsis using high-resolution manometry (HRM), with esophageal motility disorders defined using the Chicago Classification version 4.0 (CCv4.0), and secondary peristalsis using functional lumen imaging probe (FLIP) panometry.5,6 Although HRM and FLIP panometry motility diagnoses are often analogous, they can sometimes differ. For example, abnormal secondary peristalsis can occur when primary peristalsis is normal, which has been associated with reflux and non-obstructive dysphagia.7,8 This study aimed to examine the effect of age on primary peristalsis and secondary peristalsis.

Intestinal organ chips for disease modelling and personalized medicine

Alterations in intestinal structure, mechanics and physiology underlie acute and chronic intestinal conditions, many of which are influenced by dysregulation of microbiome, peristalsis, stroma or immune responses. Studying human intestinal physiology or pathophysiology is difficult in preclinical animal models because their microbiomes and immune systems differ from those of humans. Although advances in organoid culture partially overcome this challenge, intestinal organoids still lack crucial features that are necessary to study functions central to intestinal health and disease, such as digestion or fluid flow, as well as contributions from long-term effects of living microbiome, peristalsis and immune cells. Here, we review developments in organ-on-a-chip (organ chip) microfluidic culture models of the human intestine that are lined by epithelial cells and interfaced with other tissues (such as stroma or endothelium), which can experience both fluid flow and peristalsis-like motions. Organ chips offer powerful ways to model intestinal physiology and disease states for various human populations and individual patients, and can be used to gain new insight into underlying molecular and biophysical mechanisms of disease. They can also be used as preclinical tools to discover new drugs and then validate their therapeutic efficacy and safety in the same human-relevant model.

Enhancing Chicago Classification diagnoses with functional lumen imaging probe-mechanics (FLIP-MECH)

BACKGROUND

Esophageal motility disorders can be diagnosed by either high-resolution manometry (HRM) or the functional lumen imaging probe (FLIP) but there is no systematic approach to synergize the measurements of these modalities or to improve the diagnostic metrics that have been developed to analyze them. This work aimed to devise a formal approach to bridge the gap between diagnoses inferred from HRM and FLIP measurements using deep learning and mechanics.

METHODS

The "mechanical health" of the esophagus was analyzed in 740 subjects including a spectrum of motility disorder patients and normal subjects. The mechanical health was quantified through a set of parameters including wall stiffness, active relaxation, and contraction pattern. These parameters were used by a variational autoencoder to generate a parameter space called virtual disease landscape (VDL). Finally, probabilities were assigned to each point (subject) on the VDL through linear discriminant analysis (LDA), which in turn was used to compare with FLIP and HRM diagnoses.

RESULTS

Subjects clustered into different regions of the VDL with their location relative to each other (and normal) defined by the type and severity of dysfunction. The two major categories that separated best on the VDL were subjects with normal esophagogastric junction (EGJ) opening and those with EGJ obstruction. Both HRM and FLIP diagnoses correlated well within these two groups.

CONCLUSION

Mechanics-based parameters effectively estimated esophageal health using FLIP measurements to position subjects in a 3-D VDL that segregated subjects in good alignment with motility diagnoses gleaned from HRM and FLIP studies.

Endoscopic impedance planimetry versus high-resolution manometry (HRM) for pre-operative motility evaluation in anti-reflux surgery

INTRODUCTION

Pre-operative evaluation of patients with gastroesophageal reflux disease (GERD) includes assessment of esophageal motility. High-resolution manometry (HRM) is the gold standard; endoscopic impedance planimetry (IP) with Endoflip 2.0 is increasingly utilized in esophageal disorders of motility. We hypothesized that normal IP motility would correlate with normal HRM motility and tested this in a prospective cohort study.

METHODS

Patients presenting for surgical evaluation of GERD between 9/2020 and 10/2021 were prospectively enrolled under an IRB-approved protocol. Patients with prior esophageal/gastric surgery, known motility disorders, or large paraesophageal hernias were excluded. All underwent HRM and IP, with normal motility defined by Chicago 3.0 classification for HRM and the presence of repetitive antegrade contractions for IP. Logistic regression and t test were used to analyze the data; p value < 0.05 was considered significant.

RESULTS

Of 63 patients enrolled, 48 completed both IP and HRM testing. The cohort was 50% male with a median age of 52.5 [42.0, 66.0] years, mostly ASA class 1-2 (75.1%, n = 36) and had an average BMI of 31.4 ± 6.3 kg/m2. Normal motility tracings were in 62.5% of IP and 75% of HRM tests. Using HRM as the gold standard, IP detected normal motility with a sensitivity of 65.8% and a specificity of 50% (positive predictive value 83.3%, negative predictive value 27.8%). Normal IP was not statistically significant in predicting normal HRM (OR 3.182, 95% CI 0.826-12.262, p = 0.0926). Tolerability of IP was significantly better than HRM with lower rates of discomfort (10.9% vs. 93.4%, p < 0.0001) and higher willingness to repeat testing (100% vs. 47.8%, p < 0.0001).

CONCLUSION

Esophageal motility testing with Endoflip 2.0 is well tolerated by patients. The low specificity (50%), poor negative predictive value (27.8%), and lack of statistically significant concordance between IP and HRM raises concern for the reliability of this test as a stand-alone replacement for HRM in the pre-operative evaluation for GERD.

Esophageal biomechanics assessed by impedance planimetry (EndoFLIPTM) in healthy subjects and in patients with eosinophilic esophagitis. Normality values

BACKGROUND

active eosinophilic esophagitis is associated with esophageal caliber, distensibility and motility changes that may be reversed with treatment.

OBJECTIVES

to study esophageal diameter, distensibility and contractility in healthy subjects compared to patients with eosinophilic esophagitis, both before and after treatment.

METHODS

a quasi-experimental study, EndoFLIP™, was used to analyze the esophageal body and esophago-gastric junction (EGJ) in all three groups, and a program was designed to obtain esophageal diameter, distensibility and contractility values.

RESULTS

ten healthy volunteers (24-61 years, six men) and nine patients with eosinophilic esophagitis (21-52 years, seven men) were included. The esophagogastric junction distensibility index was 5.07 mm2/Hg in the control subjects, 2.40 mm2/Hg in the subjects with eosinophilic esophagitis before treatment and 2.46 mm2/Hg after treatment. The distensibility plateau was 20.02 mm, 15.43 mm and 17.41 mm, respectively, and the diameter was 21.90 mm, 17.73 mm and 18.30 mm, showing significant differences (p < 0.05), except between control subjects and patients after treatment (p = 0.079). Repetitive antegrade contractions developed in 90 % of control subjects, 66.7 % of eosinophilic esophagitis patients before treatment and 88.9 % of the latter after treatment (p > 0.05).

CONCLUSIONS

esophago-gastric junction distensibility index, distensibility plateau and diameter values were higher in controls than in patients, although six weeks of treatment seems a short period to observe significant changes in esophageal biomechanics. Repetitive antegrade contractions are the predominant pattern in healthy subjects and eosinophilic esophagitis. We provide normality values for esophageal biomechanics, measured by impedance planimetry in our setting.

The broad impact of functional lumen imaging probe panometry in addition to high-resolution manometry in an esophageal clinical practice

High-resolution manometry (HRM) with the Chicago Classification (CC) is the standard paradigm to define esophageal motility disorders. Functional lumen imaging probe (FLIP) panometry utilizes impedance planimetry to characterize esophageal compliance and secondary peristalsis. The aim of this study was to explore the clinical impact of FLIP panometry in addition to HRM. A retrospective chart review was performed on FLIP panometry cases utilizing the 322N catheter. Cases with prior foregut surgeries or botulinum injection within 6 months of FLIP panometry were excluded. EGJ-diameter and distensibility index (DI) and secondary contraction patterns at increasing balloon volumes were recorded. An EGJ-DI of ≥2.8 mm2/mm Hg at 60 mL was considered as a normal EGJ distensibility. CC diagnosis, Eckhardt score, Brief Esophageal Dysphagia Questionnaire, and clinical outcomes were obtained for each FLIP case. A total of 186 cases were included. Absent contractility and achalasia types 1 and 2 showed predominantly absent secondary contraction patterns, while type 3 had a variety of secondary contractile patterns on FLIP panometry. Among 77 cases with EGJ outflow obstruction (EGJOO), 60% had a low EGJ-DI. Among those with no motility disorder or ineffective esophageal motility on HRM, 27% had a low DI and 47% had sustained contractions on FLIP, raising concern for an esophageal dysmotility process along the achalasia and/or spastic spectrum. FLIP panometry often confirmed findings on HRM in achalasia and absent contractility. FLIP panometry is useful in characterizing EGJOO cases. Spastic features on FLIP panometry may raise concern for a motility disorder on the spastic spectrum not captured by HRM. Further studies are needed on FLIP panometry to determine how to proceed with discrepancy with HRM and explore diagnoses beyond the CC.

Advances in the Diagnosis and Management of Achalasia and Achalasia-Like Syndromes: Insights From HRM and FLIP

High-resolution manometry, Chicago Classification v4.0, the functional lumen imaging probe, Panometry, and peroral endoscopic myotomy (POEM) are all now integral parts of the landscape for managing achalasia or, more precisely, achalasia-like syndromes. This narrative review examines the impact of these innovations on the management of achalasia-like syndromes. High-resolution manometry was the disruptive technology that prompted the paradigm shift to thinking of motility disorders as patterns of obstructive physiology involving the esophagogastric junction and/or the distal esophagus rather than as siloed entities. An early observation was that the cardinal feature of achalasia-impaired lower esophageal sphincter relaxation-can occur in several subtypes: without peristalsis, with pan-esophageal pressurization, with premature (spastic) distal esophageal contractions, or even with preserved peristalsis (esophagogastric junction outlet obstruction). Furthermore, there being no biomarker for achalasia, no manometric pattern is perfectly sensitive or specific for 'achalasia' and there is also no 'gold standard' for the diagnosis. Consequently, complimentary physiological testing with a timed barium esophagram or functional lumen imaging probe are employed both to improve the detection of patients likely to respond to treatments for 'achalasia' and to characterize other syndromes also likely to benefit from achalasia therapies. These findings have become particularly relevant with the development of a minimally invasive technique for performing a tailored esophageal myotomy, POEM. Now and in the future, optimal achalasia management is to render treatment in a phenotype-specific manner, that is, POEM calibrated in a patient-specific manner for obstructive physiology including the distal esophagus and more conservative strategies such as a short POEM or pneumatic dilation for obstructive physiology limited to the lower esophageal sphincter.

Validation of Clinically Relevant Thresholds of Esophagogastric Junction Obstruction Using FLIP Panometry

BACKGROUND & AIMS

This study aimed to assess the accuracy of functional luminal imaging probe (FLIP) panometry to detect esophagogastric junction (EGJ) obstruction assigned by high-resolution manometry (HRM) and the Chicago Classification version 4.0 (CCv4.0).

METHODS

Six hundred eighty-seven adult patients who completed FLIP and HRM for primary esophageal motility evaluation and 35 asymptomatic volunteers (controls) were included. EGJ opening was evaluated with 16-cm FLIP during sedated endoscopy via EGJ-distensibility index (DI) and maximum EGJ diameter. HRM was classified according to CCv4.0 and focused on studies with a conclusive disorder of EGJ outflow (ie, achalasia subtypes I, II, or III; or EGJ outflow obstruction with abnormal timed barium esophagogram) or normal EGJ outflow.

RESULTS

All 35 controls had EGJ-DI >3.0 mm²/mmHg and maximum EGJ diameter >16 mm. Per HRM and CCv4.0, 245 patients had a conclusive disorder of EGJ outflow, and 314 patients had normal EGJ outflow. Among the 241 patients with reduced EGJ opening (EGJ-DI <2.0 mm²/mmHg and maximum EGJ diameter <12 mm) on FLIP panometry, 86% had a conclusive disorder of EGJ outflow per CCv4.0. Among the 203 patients with normal EGJ opening (EGJ-DI ≥2.0 mm²/mmHg and maximum EGJ diameter ≥16 mm) on FLIP panometry, 99% had normal EGJ outflow per CCv4.0.

CONCLUSIONS

FLIP panometry accurately identified clinically relevant conclusive EGJ obstruction as defined by CCv4.0 in patients evaluated for esophageal motor disorders. Thus, FLIP panometry is a valuable tool for both independent and complementary evaluation of esophageal motility.

The Utility of Functional Luminal Imaging Probes Measurements to Diagnose Dysmotility and Their Relationship to Impaired Bolus Clearance

BACKGROUND

Functional luminal imaging probes (FLIP) have been used by multiple centers to assess esophagogastric junction (EGJ) function in patients at risk for esophageal obstruction but its role in diagnosing peristaltic disorders is less well studied. In particular, there are no studies comparing the sensitivity of FLIP to diagnose motility abnormalities and impaired bolus transit by high-resolution esophageal manometry with impedance.

METHODS

We prospectively recruited 42 patients undergoing high-resolution esophageal manometry with impedance (HRIM) who also underwent FLIP between 2018 and 2020. HRIM parameters were analyzed using Swallow Gateway software to determine peristaltic and lower esophageal sphincter pressure measurements as well as bolus flow parameters. FLIP tracings were analyzed for the presence of repetitive antegrade contractions (RACs), EGJ distensibility, and associated parameters.

RESULTS

Forty-two patients were included (11 controls, 7 achalasia, 16 fundoplication, 8 dysmotility). The mean age of patients was 10.1 ± 0.9 years. There were significant differences in bolus flow parameters across diagnosis with longer bolus presence (BPT) in control patients compared with fundoplication and dysmotility patients. There was a significant correlation between EGJ diameter, EGJ distensibility and bolus flow time (BFT) for solid foods (r2 > 0.518, P < 0.02). The presence of RACs and EGJ relaxation during RACs was associated with a greater BFT and BPT across textures (P < 0.05). Forty-two percentage of patients with absent RACs, however, had clear peristalsis by HRIM.

CONCLUSIONS

The presence of RACs and EGJ relaxation by FLIP correlate with improved bolus flow. Patients with an absence of RACs need HRIM to confirm any diagnoses of dysmotility.

Validation of secondary peristalsis classification using FLIP panometry in 741 subjects undergoing manometry

BACKGROUND AND AIMS

This study aimed to systematically evaluate a classification scheme of secondary peristalsis using functional luminal imaging probe (FLIP) panometry through comparison with primary peristalsis on high-resolution manometry (HRM).

METHODS

706 adult patients that completed FLIP and HRM for primary esophageal motility evaluation and 35 asymptomatic volunteers ("controls") were included. Secondary peristalsis, that is, contractile responses (CRs), was classified on FLIP panometry by the presence and pattern of contractility as normal (NCR), borderline (BCR), impaired/disordered (IDCR), absent (ACR), or spastic-reactive (SRCR). Primary peristalsis on HRM was assessed according to the Chicago Classification.

RESULTS

All 35 of the controls had antegrade contractions on FLIP panometry with either NCR (89%) or BCR (11%). The average percentages of normal swallows on HRM varied across contractile response patterns from 84% in NCR, 68% in BCR, 39% in IDCR, to 11% in ACR, as did the percentage of failed swallows on HRM: 4% in NCR, 12% in BCR, 36% in IDCR, and 79% in ACR. SRCR on FLIP panometry was observed in 18/57 (32%) patients with type III achalasia, 4/15 (27%) with distal esophageal spasm, and 7/15 (47%) with hypercontractile esophagus on HRM.

CONCLUSIONS

The FLIP panometry contractile response patterns reflect a pathophysiologic transition from normal to abnormal esophageal peristaltic function with shared features with primary peristaltic function/dysfunction on HRM. Thus, these patterns of the contractile response to distension can facilitate the evaluation of esophageal motility using FLIP panometry.

Classifying Esophageal Motility by FLIP Panometry: A Study of 722 Subjects With Manometry

INTRODUCTION

Functional luminal imaging probe (FLIP) panometry can evaluate esophageal motility in response to sustained esophageal distension at the time of sedated endoscopy. This study aimed to describe a classification of esophageal motility using FLIP panometry and evaluate it against high-resolution manometry (HRM) and Chicago Classification v4.0 (CCv4.0).

METHODS

Five hundred thirty-nine adult patients who completed FLIP and HRM with a conclusive CCv4.0 diagnosis were included in the primary analysis. Thirty-five asymptomatic volunteers ("controls") and 148 patients with an inconclusive CCv4.0 diagnosis or systemic sclerosis were also described. Esophagogastric junction (EGJ) opening and the contractile response (CR) to distension (i.e., secondary peristalsis) were evaluated with a 16-cm FLIP during sedated endoscopy and analyzed using a customized software program. HRM was classified according to CCv4.0.

RESULTS

In the primary analysis, 156 patients (29%) had normal motility on FLIP panometry, defined by normal EGJ opening and a normal or borderline CR; 95% of these patients had normal motility or ineffective esophageal motility on HRM. Two hundred two patients (37%) had obstruction with weak CR, defined as reduced EGJ opening and absent CR or impaired/disordered CR, on FLIP panometry; 92% of these patients had a disorder of EGJ outflow per CCv4.0.

DISCUSSION

Classifying esophageal motility in response to sustained distension with FLIP panometry parallels the swallow-associated motility evaluation provided with HRM and CCv4.0. Thus, FLIP panometry serves as a well-tolerated method that can complement, or in some cases be an alternative to HRM, for evaluating esophageal motility disorders.

Dysphagia: Novel and Emerging Diagnostic Modalities

Among recent advances in diagnostics for dysphagia and esophageal motility disorders is the update to the Chicago Classification (version 4.0) for interpretation of high-resolution manometry (HRM) and diagnosis of esophageal motility disorders. The update incorporates application of complementary testing strategies during HRM, such as provocative HRM maneuvers, and recommendation for barium esophagram or functional luminal imaging probe (FLIP) panometry to help clarify inconclusive HRM findings. FLIP panometry also represents an emerging technology for evaluation of esophageal distensibility and motility at the time of endoscopy.

Evaluating esophageal motility beyond primary peristalsis: Assessing esophagogastric junction opening mechanics and secondary peristalsis in patients with normal manometry

BACKGROUND

Functional luminal imaging probe (FLIP) Panometry assesses the esophageal response to distention and may complement the assessment of primary peristalsis on high-resolution manometry (HRM). We aimed to investigate whether FLIP Panometry provides complementary information in patients with normal esophageal motility on HRM.

METHODS

Adult patients that completed FLIP and had an HRM classification of normal motility were retrospectively identified for inclusion. 16-cm FLIP studies performed during endoscopy were evaluated to assess EGJ distensibility, secondary peristalsis, and identify an abnormal response to distention involving sustained LES contraction (sLESC). Clinical characteristics and esophagram were assessed when available.

KEY RESULTS

Of 164 patients included (mean(SD) age 48(16) years, 75% female), 111 (68%) had normal Panometry with EGJ-distensibility index (DI) ≥2.0 mm2 /mmHg, maximum EGJ diameter ≥16mm and antegrade contractions. Abnormal EGJ distensibility was observed in 44/164 (27%), and 38/164 (23%) had an abnormal contractile response to distension. sLESC was observed in 11/164 (7%). Among 68 patients that completed esophagram, abnormal EGJ distensibility was more frequently observed with an abnormal esophagram than normal EGJ opening: 14/23 (61%) vs 10/45 (22%); P=0.003. Epiphrenic diverticula were present in 3/164 patients: 2/3 had sLESC.

CONCLUSIONS & INFERENCES

Symptomatic patients with normal esophageal motility on HRM predominantly have normal FLIP Panometry; however, abnormal FLIP findings can be observed. While abnormal Panometry findings appear clinically relevant via an association with abnormal bolus retention, complementary tests, such as provocative maneuvers with HRM and timed barium esophagram, are useful to determine clinical context.

Chicago Classification update (version 4.0): Technical review on diagnostic criteria for achalasia

The recommended diagnostic criteria for achalasia have been recently updated by Chicago Classification version 4.0 (CCv4.0), the widely accepted classification scheme for esophageal motility disorders using metrics from high-resolution manometry (HRM). CCv4.0 continued upon prior versions by subtyping achalasia into type I, type II, and type III on HRM. The achalasia subgroup of the CCv4.0 Working Group developed both conclusive and inconclusive statements for the HRM diagnoses of achalasia subtypes. Conclusive achalasia on HRM is defined as an abnormal median integrated relaxation pressure (IRP) in the primary position of wet swallows along with 100% failed peristalsis, with type I achalasia having 100% failed peristalsis without panesophageal pressurization (PEP), type II achalasia with PEP in at least 20% of swallows, and type III achalasia having at least 20% of swallows premature with no appreciable peristalsis. An inconclusive HRM diagnosis of achalasia can arise when there is an integrated relaxation pressure (IRP) that is borderline or at the upper limit of normal in at least one position, there is an abnormal IRP in both positions but evidence of peristalsis with PEP or premature swallows, or there is peristalsis in the secondary position after apparent achalasia in the primary position. In patients with dysphagia and an inconclusive HRM diagnosis of achalasia, supportive testing beyond HRM such as a timed barium esophagram (TBE) for functional lumen imaging probe (FLIP) is recommended. The review recommends a diagnostic algorithm for achalasia, discusses therapeutic options for the disease, and outlines future needs on this topic.

Esophagogastric Junction Opening Parameters Are Consistently Abnormal in Untreated Achalasia

Achalasia is a disorder of impaired lower esophageal sphincter (LES) relaxation and failed peristalsis traditionally characterized by manometry.¹ As impaired LES relaxation is a mechanism of reduced esophagogastric junction (EGJ) opening, abnormally reduced EGJ distensibility assessed with functional luminal imaging probe (FLIP) was reported among patients with untreated achalasia.^2-5 Therefore, we aimed to describe the performance characteristics of EGJ opening parameters on FLIP panometry among a large cohort of treatment-naïve achalasia patients.

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.

Achalasia subtypes can be identified with functional luminal imaging probe (FLIP) panometry using a supervised machine learning process

BACKGROUND

Achalasia subtypes on high-resolution manometry (HRM) prognosticate treatment response and help direct management plan. We aimed to utilize parameters of distension-induced contractility and pressurization on functional luminal imaging probe (FLIP) panometry and machine learning to predict HRM achalasia subtypes.

METHODS

One hundred eighty adult patients with treatment-naïve achalasia defined by HRM per Chicago Classification (40 type I, 99 type II, 41 type III achalasia) who underwent FLIP panometry were included: 140 patients were used as the training cohort and 40 patients as the test cohort. FLIP panometry studies performed with 16-cm FLIP assemblies were retrospectively analyzed to assess distensive pressure and distension-induced esophageal contractility. Correlation analysis, single tree, and random forest were adopted to develop classification trees to identify achalasia subtypes.

KEY RESULTS

Intra-balloon pressure at 60 mL fill volume, and proportions of patients with absent contractile response, repetitive retrograde contractile pattern, occluding contractions, sustained occluding contractions (SOC), contraction-associated pressure changes >10 mm Hg all differed between HRM achalasia subtypes and were used to build the decision tree-based classification model. The model identified spastic (type III) vs non-spastic (types I and II) achalasia with 90% and 78% accuracy in the train and test cohorts, respectively. Achalasia subtypes I, II, and III were identified with 71% and 55% accuracy in the train and test cohorts, respectively.

CONCLUSIONS AND INFERENCES

Using a supervised machine learning process, a preliminary model was developed that distinguished type III achalasia from non-spastic achalasia with FLIP panometry. Further refinement of the measurements and more experience (data) may improve its ability for clinically relevant application.

Normal Functional Luminal Imaging Probe Panometry Findings Associate With Lack of Major Esophageal Motility Disorder on High-Resolution Manometry

BACKGROUND & AIMS

A normal esophageal response to distension on functional luminal imaging probe (FLIP) panometry during endoscopy might indicate normal esophageal motor function. We aimed to investigate the correlation of normal FLIP panometry findings with esophageal high-resolution manometry (HRM) and outcomes of discrepant patients.

METHODS

We performed a retrospective study using data from a registry of patients who completed FLIP during sedated endoscopy. We identified 111 patients with normal FLIP panometry findings (mean age, 42 y; 69% female) and corresponding HRM data. A normal FLIP panometry was defined as an esophagogastric junction (EGJ) distensibility index greater than 3.0 mm2/mm Hg, an absence of repetitive retrograde contractions, and a repetitive antegrade contraction pattern that met the Rule-of-6s: ≥6 consecutive antegrade contractions of ≥6-cm in length, at a rate of 6 ± 3 contractions per minute. HRM findings were classified by the Chicago classification system version 3.0.

RESULTS

HRM results were classified as normal motility in 78 patients (70%), ineffective esophageal motility in 10 patients (9%), EGJ outflow obstruction in 20 patients (18%), and 3 patients (3%) as other. In patients with EGJ outflow obstruction based on HRM, the integrated relaxation pressure normalized on adjunctive swallows in 16 of 20 patients (80%), and in 8 of 9 patients (88%) who completed a barium esophagram and had normal barium clearance. Thus, although 23 of 111 patients (21%) with normal FLIP panometry had abnormal HRM findings, these HRMs often were considered to be false-positive or equivocal results. All patients with an abnormal result from HRM were treated conservatively.

CONCLUSIONS

In a retrospective cohort study, we found that patients with normal FLIP panometry results did not have a clinical impression of a major esophageal motor disorder. Normal FLIP panometry results can exclude esophageal motility disorders at the time of endoscopy, possibly negating the need for HRM in select patients.

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

The goal of this study was to conceptualize and compute measures of "mechanical work" done by the esophagus using data generated during functional lumen imaging probe (FLIP) panometry and compare work done during secondary peristalsis among patients and controls. Eighty-five individuals were evaluated with a 16-cm FLIP during sedated endoscopy, including asymptomatic controls (n = 14) and those with achalasia subtypes I, II, and III (n = 15, each); gastroesophageal reflux disease (GERD; n = 13); eosinophilic esophagitis (EoE; n = 9); and systemic sclerosis (SSc; n = 5). The FLIP catheter was positioned to have its distal segment straddling the esophagogastric junction (EGJ) during stepwise distension. Two metrics of work were assessed: "active work" (during bag volumes ≤ 40 mL where contractility generates substantial changes in lumen area) and "work capacity" (for bag volumes ≥ 60 mL when contractility cannot substantially alter the lumen area). Controls showed median [interquartile range (IQR)] of 7.3 (3.6-9.2) mJ of active work and 268.6 (225.2-332.3) mJ of work capacity. Patients with all achalasia subtypes, GERD, and SSc showed lower active work done than controls (P ≤ 0.003). Patients with achalasia subtypes I and II, GERD, and SSc had lower work capacity compared with controls (P < 0.001, 0.004, 0.04, and 0.001, respectively). Work capacity was similar between controls and patients with achalasia type III and EoE. Mechanical work of the esophagus differs between healthy controls and patient groups with achalasia, EoE, SSc, and GERD. Further studies are needed to fully explore the utility of this approach, but these work metrics would be valuable for device design (artificial esophagus), to measure the efficacy of peristalsis, to gauge the physiological state of the esophagus, and to comment on its pumping effectiveness.NEW & NOTEWORTHY Functional lumen imaging probe (FLIP) panometry assesses esophageal response to distension and provides a simultaneous assessment of pressure and dimension during contractility. This enables an objective assessment of "mechanical work" done by the esophagus. Eighty-five individuals were evaluated, and two work metrics were computed for each subject. Controls showed greater values of work compared with individuals with achalasia, gastroesophageal reflux disease (GERD), and systemic sclerosis (SSc). These values can quantify the mechanical behavior of the distal esophagus and assist in the estimation of muscular integrity.

Repetitive Antegrade Contractions: A novel response to sustained esophageal distension is modulated by cholinergic influence

BACKGROUND & AIMS

A unique motor response to sustained esophageal distension, repetitive antegrade contractions (RACs), is observed using functional luminal imaging probe (FLIP) panometry. However, physiologic mechanisms related to this response are unexplored. This study aimed to evaluate the impact of cholinergic inhibition with atropine on the esophageal contractile response to sustained distention, including RACs, among healthy volunteers.

METHODS

8 asymptomatic volunteers (ages 22-45) were evaluated in a crossover study design with 16-cm FLIP positioned across the esophagogastric junction and distal esophagus during sedated upper endoscopy. The FLIP study involving stepwise volumetric distension was performed twice in each subject, at baseline and again after atropine (15 mcg/kg) was administered intravenously. FLIP panometry was analyzed to assess the contractile response to distension.

RESULTS

Antegrade contractions, lumen-occluding contractions, and a RAC pattern were observed in 8/8, 8/8, and 7/8(88%) subjects, respectively, at baseline and in 5/8 (63%), 2/8 (25%) and 2/8 (25%) subjects after atropine. The rate of contractions in the RAC pattern was similar (6-7 contractions per minute) before and after atropine. Compared with the baseline study, distension-induced contractility was triggered at higher fill volumes after atropine. FLIP pressures were lower in response to volumetric filling after atropine than at baseline.

CONCLUSIONS

The vigor and triggering of the esophageal contractile response to distension is reduced by cholinergic inhibition in asymptomatic controls. The observation that the rate of contractions did not change when patients developed repetitive contractile responses suggests that this rate is not modified by cholinergic inhibition once contractility is triggered.

Esophageal Functional Lumen Imaging Probe (FLIP): How Can FLIP Enhance Your Clinical Practice?

Recent innovations in esophageal diagnostic testing have enhanced gastroenterology clinical practice by facilitating more nuanced and advanced evaluation of esophageal symptoms. Among these pivotal advances is the FDA-approved functional lumen imaging probe (FLIP), which utilizes impedance planimetry via volumetric distension of a catheter-mounted balloon at the time of sedated upper endoscopy, to acquire esophageal dimensions and pressures. In real time, FLIP can display cross-sectional areas (CSA) and distensibility indices (ratios of CSA to intra-balloon pressures) throughout the esophagus, most notably at the esophagogastric junction, as well as secondary peristaltic esophageal body contractile patterns. As the use of FLIP has progressively spread and permeated into the practice of clinical gastroenterology since its introduction, increasing data on and experiences with its applications have accumulated to guide its utility in clinical practice. In this current review developed for gastroenterologists and foregut surgeons across clinical practice, we provide an introduction to FLIP technology and metrics and discuss the clinical scenarios in which performance of or referral for FLIP may be helpful in the evaluation and management of patients with commonly encountered esophageal symptoms and disorders. Specifically, we discuss the potential applications and limitations of FLIP as a complementary diagnostic modality in patients with non-obstructive dysphagia, established or suspected achalasia spectrum disorders, eosinophilic esophagitis, gastroesophageal reflux disease and those undergoing esophageal surgery.

The use of impedance planimetry (Endoscopic Functional Lumen Imaging Probe, EndoFLIP® ) in the gastrointestinal tract: A systematic review

BACKGROUND AND PURPOSE

The EndoFLIP® system is a method of delineating impedance and was first designed to investigate the characteristics of the esophago-gastric junction. In the last decade, its use was widened to investigate other sphincteric and non-sphincteric systems of the gastrointestinal tract. The objective of the present systematic review was to summarize the available data in literature on the use of the EndoFLIP® system in the gastrointestinal tract, including sphincteric and non-sphincteric regions. We performed a systematic review in accordance with recommendations for systematic review using PRISMA guidelines without date restriction, until June 2020, using MEDLINE-PubMed, Cochrane Library, and Google Scholar databases. Only articles written in English were included in the present review. Five hundred and six unique citations were identified from all database combined. Of those, 95 met the inclusion criteria. There was a lack of standardization among studies in terms of anesthetic drugs use, probe placement, and inflation protocol. In most cases, only small cohorts of patients were included. Most studies investigated the EGJ, with a potential use of the EndoFLIP® to identify a subgroup of patients with achalasia and for intraoperative assessment of treatment efficacy in achalasia. However, the use of EndoFLIP® in the esophageal body (esophageal panometry), other esophageal diseases (gastro-esophageal reflux disease, eosinophilic esophagitis), and other sphincter regions (anal canal, pylorus) will need further confirmatory studies. The EndoFLIP® system provides detailed geometric data of the gastrointestinal lumen but further works are needed to determine its use in clinical practice.