The major aims of this investigation were (i) to establish normal limits of peristaltic integrity in EPT terms based on a systematic analysis of a large series of control subjects; and (ii) to develop a classification scheme for weak peristalsis based on a comparison between control subjects and a cohort of patients with unexplained non-obstructive dysphagia intended for use in clinical EPT studies. The major findings were that the segmental architecture of peristalsis was highly stereotyped among subjects as were defects in that architecture associated with IBT for individual subjects: large (> 5 cm) and small (2–5 cm) breaks in the 20 mm Hg isobaric contour of the peristaltic contraction. Although encountered in only about one-third of the 113 patients studied, frequent large and small breaks in the 20 mm Hg isobaric contour were significantly more common in the dysphagia patients than in control subjects. Failed peristalsis, the other mechanism of IBT observed in the HRIM studies occurred no more frequently in the dysphagia population than in the control subjects. Based on these observations, we propose an EPT classification of weak peristalsis based on the occurrence of breaks in the 20 mm Hg isobaric contour wherein weak peristalsis with large breaks is defined by those occurring with > 20 % of swallows and weak peristalsis with small breaks defined by those occurring with > 30 % of swallows.
A common indication for esophageal function testing is in the evaluation of unexplained dysphagia. Findings of indisputable significance are the detection of major motor disorders or absent peristalsis. However, those findings are relatively uncommon. More frequent is the finding of hypotensive or mildly disordered peristalsis, the significance of which is less certain (14
). Acknowledging that caveat, IBT seems a reasonable surrogate end point for gauging the adequacy of peristalsis. IBT occurs more frequently with weak peristalsis. Kahrilas et al.
) reported that IBT invariably occurred in distal esophagus when peristaltic amplitude was < 20 mm Hg, whereas it rarely occurred when the peristaltic amplitude was 31–45 mm Hg. Moreover, IBT is associated with dysphagia. In a study of 350 patients, IBT occurred in 51 % of patients with dysphagia compared with 30 % of patients without dysphagia (6
). Consequently, we evaluated EPT defects associated with IBT in HRIM studies as potentially linked to dysphagia. Consistent with previous investigations (7
), we found that failed peristaltic contractions and EPT plots with breaks in the 20 mm Hg isobaric contour were associated with IBT. EPT plots with breaks > 5 cm (large) were nearly uniformly associated with IBT; 2–5 cm (small) breaks were variably associated with IBT (). Topography plots without breaks or with breaks in the 20 mm Hg isobaric contour < 2 cm in length uniformly achieved complete bolus transit.
Previous impedance manometry studies found that 30 % of swallows with IBT to be the upper limit of normal (10
). The normative data in generally support that finding. However, we found that although small and large breaks in 20 mm Hg IBC occurred more frequently in the dysphagic patients than in the control subjects, this was not so for failed peristalsis. A caveat to this is that patients with absent peristalsis (100 % failed) were considered to have a major motility disturbance and excluded from this analysis at the outset. Consequently, in the proposed classification, frequently failed peristalsis was considered as its own entity and not included as an element in definition of weak peristalsis ().
The finding that frequent large or small breaks in the 20 mm Hg IBC occurred significantly more frequently in a carefully selected patient population with unexplained dysphagia suggests that this mechanism may explain dysphagia in some patients with normal esophagogastric junction relaxation, no hiatal hernia, no stricture or ring, no finding suggestive of eosinophilic esophagitis, and no major motility disorder. Although this was possibility suggested in a previous case report (7
) and in an analysis of transition zone defects (18
), this is the first study to our knowledge that systematically evaluated these phenomena in a large cohort of patients with unexplained dysphagia.
This study has limitations, one of which is potential age bias between control subjects (mean 27 years, range 19–48 years) and dysphagia patients (mean 46 years, range 21–76 years). Subdividing the dysphagia group into those younger or older than 45 years, we found no significant age effect, but the possibility of bias remains, and including older control subjects into a subsequent analysis could potentially increase the number of swallows with breaks in the 20 mm Hg isobaric contour defining weak peristalsis. Another potential limitation of the study was that the HRIM analysis was based on only 16 normal subjects studied with the Sierra HRIM device. However, the HRIM data were largely confirmatory of previous results obtained with another HRIM system (Medical Measurements Systems, Enschede, The Netherlands) in a similar analysis of another 24 subjects (10
). Finally, the use of provocative testing with solid or volume challenge in correlation with symptom assessment may be shown to improve the diagnostic yield of EPT studies in the future (19
In summary, we utilized a large set of control subjects to define the stereotypic features of EPT common among subjects and then to define normal limits for EPT features associated with IBT as verified by HRIM. The defining features of weak peristalsis (), frequent large or small breaks in the 20 mm Hg isobaric contour, occurred significantly more frequent in dysphagia patients than in control subjects making this a potential explanation for unexplained dysphagia. The therapeutic implications of these findings, both with respect to tolerance of antireflux surgery and responsiveness to pharmacological intervention with pro-motility drugs will need to be the focus of future research.
WHAT IS CURRENT KNOWLEDGE
- Esophageal peristaltic amplitudes > 30 mm Hg are normally associated with complete bolus transit, but impedance studies suggest that this threshold poorly predicts incomplete bolus transit (IBT).
- Esophageal pressure topography (EPT) studies demonstrate a segmental architecture of peristalsis characterized by non-uniform peristaltic amplitude with discrete segments of contraction and intervening pressure troughs.
- High-resolution impedance manometry shows that IBT occurs at pressure troughs in EPT plots and with failed peristalsis.
WHAT IS NEW HERE
- Computer simulation was used to extract the stereotypic features of EPT plots in control subjects and establish normal limits for failed peristalsis and for the dimensions and occurrence of critical pressure troughs in peristalsis.
- Large (> 5 cm) and small (2–5 cm) pressure troughs in the 20 mm Hg isobaric contour of peristalsis, but not failed peristalsis, occurred more frequently in patients with unexplained non-obstructive dysphagia than in control subjects.
- A classification scheme for peristaltic integrity is proposed in EPT terms establishing quantitative and qualitative limits for pressure troughs and failed peristalsis intended for use in clinical EPT studies.