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 mmHg cm(-1) s(-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 ± 135.1 mmHg cm(-1)  s(-1) , segment 3: 2115.2±218.6 mmHg cm(-1) s(-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.