High resolution manometry patterns distinguish acid sensitivity in non-cardiac chest pain

Background High resolution manometry (HRM) has demonstrated two distinct smooth muscle contraction segments in the esophageal body; changes in these segments typify certain esophageal disorders. We investigated segmental characteristics in subgroups of non-cardiac chest pain (NCCP). Methods 32 NCCP subjects were segregated into a GERD group (ambulatory pH testing off antisecretory therapy showing elevated total acid exposure time, AET≥4.0% and positive symptom association probability, SAP) and an acid sensitive group (normal AET and positive SAP). HRM Clouse plots were analyzed; smooth muscle segment lengths, pressure amplitude peaks were measured for segment 2 and segment 3 (proximal and distal smooth muscle segments). Pressure volumes were determined in mmHgcm ^-1s ^-1 for each peristaltic segment, and ratios of segment 3:segment 2 calculated. Values were compared to a cohort of 14 normal controls. Key Results A distinctive shift in peak contraction amplitude to segment 3 was evident in the acid sensitive group (segment 2, 100.03± 11.06mmHg, segment 3, 145.23±10.29mmHg, P=0.006). Pressure volumes were similarly shifted to segment 3 (segment 2: 855.3±135.1mmHgcm ^-1s ^-1, segment 3: 2115.2±218.6mmHgcm ^-1s ^-1, P<0.005). In contrast, peak amplitude and pressure volume were near equal in the two segments in GERD and control groups. A threshold segment 3:segment 2 pressure volume ratio of 1.9 had the best performance characteristic for segregating acid sensitivity subjects from all GERD and control subjects. Conclusions & Inferences Shift in contractile vigor to the third peristaltic segment may be seen in acid sensitive subjects. HRM characteristics of smooth muscle contraction segments are of value in making this determination.