MODULATION OF NEUROCARDIAC FUNCTION BY ESOPHAGEAL STIMULATION IN HUMANS

1. The heart and the oesophagus have similar sensory pathways, and sen sations originating from the oesophagus are often difficult to differe ntiate from those of cardiac origin. We hypothesized that oesophageal sensory stimuli could alter neurocardiac function through autonomic re flexes elicited by these oesophageal stimuli. In the present study, we examined the neurocardiac response to oesophageal stimulation and the effects of electrical and mechanical oesophageal stimulation on the p ower spectrum of beat-to-beat heart rate variability in male volunteer s. 2. In 14 healthy volunteers, beat-to-beat heart rate compared at re st and during stimulation, using either electrical (200 mu s, 16 mA, 0 .2 Hz) or mechanical (0.5 s, 14 mi, 0.2 Hz) stimuli. The power spectru m of beat-to-beat heart rate variability was obtained and its low- and high-frequency components were determined. 3. Distal oesophageal stim ulation decreased heart rate slightly (both electrical and mechanical) (P < 0.005), and markedly altered heart rate variability (P < 0.001). Both electrical and mechanical oesophageal stimulation increased the absolute and normalized area of the high-frequency band within the pow er spectrum (P < 0.001), while simultaneously decreasing the low-frequ ency power (P < 0.005). 4. In humans, oesophageal stimulation, whether electrical or mechanical, appears to amplify respiratory-driven cardi ac vagoafferent modulation while decreasing sympathetic modulation. Th e technique provides access to vagoafferent fibres and thus may yield useful information on the autonomic effects of visceral or oesophageal sensory stimulation.