Characteristics of transient lower esophageal sphincter relaxation in humans.

Transient lower esophageal sphincter relaxations (TLESR) were studied in 10 normal healthy subjects. Electrical activity of mylohyoid muscle measured by an electromyogram (MEMG), pressures from pharynx, three esophageal sites, lower esophageal sphincter, and stomach were simultaneously recorded for 1 h, while fasting and 3 h after an 850 kcal meal. Reflux of acid into esophagus and/or occurrence of belching accompanying a TLESR was also monitored. TLESRs occurred with an equal frequency in fasting and postprandial state (6.2 vs. 6.4 h). However, frequency of an acid reflux during a TLESR was much greater postprandially than after fasting (44.8 vs. 9.6%). Belching coincided with 8% of TLESRs. A small MEMG complex and a small pharyngeal complex were present at onset of TLESR in 41.6 and 26.9% of instances, respectively. TLESRs were then categorized as either postswallow, if it occurred within 10 s of a preceding swallow-induced LES relaxation, or isolated, if its onset to previous swallow was greater than 10 s. Esophageal contractions were noticed at onset of 84% of isolated TLESRs. When present at two distal sites, this contraction was always of a simultaneous nature. Esophageal contractions at onset of postswallow TLESR were less frequent (33.3%) but when present were usually observed at the proximal esophageal site. At completion of a TLESR, the LES never recovered without an associated esophageal contraction, the latter was either swallow mediated or a spontaneous simultaneous esophageal contraction. Our data indicate that 1) MEMG and pharyngeal motor events may accompany TLESRs; and 2) esophageal contraction frequently heralds the onset, and it always occurs at completion of a TLESR.(ABSTRACT TRUNCATED AT 250 WORDS)