Address correspondence to: Amit Patel, MD, Assistant Professor of Medicine, Division of Gastroenterology, Duke University School of Medicine, DUMC Box 3913, Durham, NC 27710, USA. Email: amit.patel@duke.edu © The Author(s) 2020. Published by Oxford University Press on behalf of International Society for Diseases of the Esophagus. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com Diseases of the Esophagus (2020)33,1–6 DOI: 10.1093/dote/doaa063 Original Article Esophageal contractile segment impedance from high-resolution impedance manometry correlates with mean nocturnal baseline impedance and acid exposure time from 24-hour pH-impedance monitoring Anthony Horton, 1,2 Shai Posner, 1,2 Brian Sullivan, 1,2 Jennifer Cornejo, 2 Andrea Davis, 2 Monika Fields, 2 Thasha McIntosh, 2 Ziad Gellad, 1,2 Rahul Shimpi, 1 C. Prakash Gyawali, 3 Amit Patel, 1,2 1 Division of Gastroenterology, Duke University School of Medicine, Durham, NC, USA, 2 Division of Gastroenterol- ogy, Durham Veterans Affairs Medical Center, Durham, NC, USA, and 3 Division of Gastroenterology, Washington University School of Medicine, St Louis, MO, USA SUMMARY. Esophageal baseline impedance (BI) acquired during esophageal contraction (contractile segment impedance [CSI]) is proposed to improve BI accuracy in gastroesophageal reflux disease (GERD). We evaluated associations between CSI and conventional and novel GERD metrics. We analyzed high-resolution impedance manometry (HRIM) and ambulatory pH-impedance studies from 51 patients (58.6 ± 1.5 years; 26% F) with GERD symptoms studied off antisecretory therapy. Patients with achalasia or absent contractility were excluded. CSI (averaged across 10 swallows) and BI-HRIM (from the resting landmark phase) were acquired from the distal impedance sensors (distal sensor and 5 cm above the lower esophageal sphincter). Acid exposure time (AET) and mean nocturnal baseline impedance (MNBI) were calculated. Associations between CSI, BI-HRIM, MNBI, and AET were evaluated using correlation (Pearson) and receiver operating characteristic (ROC) analysis. Presenting symptoms included heartburn (67%), regurgitation (12%), cough (12%), and chest pain (10%). CSI-distal and CSI-5 each correlated with BI-HRIM, AET, and distal MNBI. Associations with AET were numerically stronger for CSI-distal (r =−0.46) and BI-HRIM-distal (r =−0.44) than CSI-5 (r =−0.33), BI-HRIM-5 (r =−0.28), or distal MNBI (r < −0.36). When compared to AET <4%, patients with AET >6% had significantly lower CSI- distal and BI-HRIM-distal values but not CSI-5, BI-HRIM-5, or MNBI. ROC areas under the curve for AET >6% were numerically higher for CSI-distal (0.81) than BI-HRIM-distal (0.77), distal MNBI (0.68–0.75), CSI-5 (0.68), or BI-HRIM-5 (0.68). CSI from HRIM studies inversely correlates with pathologic AET and has potential to augment the evaluation of GERD. KEY WORDS: gastroesophageal reflux disease, ambulatory reflux monitoring, pH-impedance monitoring, contractile segment impedance, distal baseline impedance, mean nocturnal baseline impedance. INTRODUCTION When esophageal symptoms suspicious for gastroe- sophageal reflux disease (GERD) persist despite a trial of antisecretory therapy and upper endoscopy is negative, esophageal function testing is typically performed for evaluation of symptoms. 1 – 3 In addi- tion to ruling out confounding diagnoses (such as achalasia spectrum disorders or rumination) and assessing peristaltic performance, esophageal manometry localizes the lower esophageal sphincter (LES) for proper positioning of the pH or pH- impedance catheter. 4, 5 Ambulatory reflux monitoring assesses reflux burden using acid exposure time (AET) and reflux-symptom association (RSA) with symptom index (SI) and symptom association probability (SAP), with the purpose of phenotyping GERD to guide management and predict treatment outcomes. 6 , 7 However, catheter-based ambulatory reflux mon- itoring results in patient discomfort and disruption of daily routines and only provides cross-sectional assessment of reflux burden accurate for the day of monitoring, without insight on day-to-day variations in acid burden or long-term mucosal injury from reflux. Consequently, esophageal baseline impedance (BI) has emerged as a surrogate for esophageal mucosal integrity, which may equate with longitudinal reflux injury over time and may predict GERD treatment outcomes with potentially less cumbersome 1 Downloaded from https://academic.oup.com/dote/article/33/12/doaa063/5865407 by guest on 27 June 2022