Effect of inter-swallow interval on striated esophagus peristalsis; a comparative study with smooth muscle esophagus

Abstract

Background: Effect of inter-swallow interval on the contractility of smooth muscle esophagus is well-documented. However, the effects on peristalsis of the striated esophagus have not been systematically studied. A better understanding of striated esophagus motor function in health and disease may enhance the interpretation of manometric studies and inform clinical care. The aim of this study was to assess the effect of inter-swallow interval on striated esophagus compared to findings with that of the smooth muscle esophagus.

Methods: We performed two sets of studies to (1) determine the effect of various inter-swallow interval in 20 healthy volunteers and (2) assess the effect of ultra-short swallow intervals facilitated by straw drinking in 28 volunteers. We analyzed variables using ANOVA with Tukey's pairwise comparison and paired t-test.

Key results: Unlike smooth muscle esophagus, the striated esophagus contractile integral did not change significantly for swallow intervals ranging from 30 to 5 s. On the contrary, striated esophagus demonstrated absent or reduced peristalsis in response to ultra-short (<2 s) intervals during straw-facilitated multiple rapid swallows.

Conclusions and inferences: Striated esophagus peristalsis is subject to manometrically observed inhibition during swallows with ultra-short intervals. Inter-swallow intervals as short as 5 s that inhibit smooth muscle esophagus peristalsis do not inhibit striated muscle peristalsis. The mechanisms of these observations are unknown but may relate to central or myenteric nervous system influences or the effects of pharyngeal biomechanics.

Keywords: MRS sequences; manometry; peristalsis; smooth muscle esophagus; striated muscle esophagus.

Figure 1:

Examples of the effect of 5 second inter-swallow interval on St.Eso and Sm.Eso contractile integrals. As seen at this interval the Sm.Eso was either completely inhibited or reduced whereas the St.Eso Contractile Integral was preserved. A and C represent the baseline swallows at 30 second intervals; B and D represent swallows at 5 second intervals.

Figure 2:

Effect of swallow interval on Sm.Eso average contractile integral in supine (2A) and upright (2B) positions. Sm.Eso contractile integral was higher in supine than in upright position for all inter-swallow intervals. Furthermore, in both positions, there was a direct relationship between magnitude of Sm.Eso CI and duration of inter-swallow interval in that the shorter the duration, the lower the CI.

Figure 3:

Effect of swallow interval on St.Eso average CI in supine (3A) and upright (3B) positions. St.Eso CI in supine position was significantly higher than in upright position for all swallow intervals. However, contrary to Sm.Eso in both positions, St.Eso CI was not significantly affected by inter-swallow intervals ranging from 30 to 5 seconds.

Figure 4:

Example of the effect of Multiple Rapid Swallow (with inter-swallow intervals of less than two seconds) on St.Eso peristalsis. As seen at this rate, the St.Eso is completely inhibited as studied by manometry. Figure 1A shows the HRM isocontour plot and figure 1B shows the corresponding line graph.

Figure 5:

Schematic diagram of St.Eso and Sm.Eso concordance and discordance of CI augmentation or reduction responses to MRS challenge. Concordance and discordance between St.Eso and Sm.Eso were frequently demonstrated in response to MRS.

Figure 6:

Residual CI for St.Eso and Sm.Eso: Average residual esophageal body contractile integral during MRS is shown. Sm.Eso exhibited lower CI during MRS which suggests more susceptibility to inhibition compared to St.Eso in both upright and supine positions.*p<0.05 for St.Eso vs Sm.Eso; †p<0.05 for supine vs upright position.