Gastric dilation during stimulation of cardiac sensory receptors.

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Abstract
Gastrointestinal symptoms are more common in patients with inferoposterior myocardial infarction than in patients with anterior infarction. These symptoms are often associated with bradycardia and hypotension, which may be caused by stimulation of sensory endings in the heart. If stimulation of cardiac sensory receptors (the Bezold-Jarisch reflex) in dogs produces gastric responses, and if stimulation of receptors in the inferoposterior wall of the left ventricle produces larger gastric responses than stimulation of receptors in the anterior wall were studied. Gastric dilation was measured from increases in volume of a gastric balloon maintained at constant distending pressure. Cardiac sensory receptors in the inferoposterior wall (circumflex coronary artery) and in the anterior wall (anterior descending artery) were stimulated separately by intracoronary injection of veratridine in choralose-anesthetized dogs. Intracoronary injection of veratridine produced bradycardia, hypotension and gastric dilation. Decreases in heart rate and increases in gastric volume produced by injection of veratridine into the circumflex artery were greater than those that resulted from injection into the anterior descending artery (32 .+-. 10 ml vs. 14 .+-. 5 ml, respectively; P < 0.05). Flow in these 2 beds and the weight of myocardium perfused by each vessel were not different. Diaphragmatic vagotomy abolished the gastric response but not the bradycardiac or hypotensive response to intracoronary injection of veratridine. Intracoronary administration of lidocaine and bilateral cervical vagotomy blocked all reflex responses to intracoronary veratridine. Stimulation of cardiac receptors with vagal afferent pathways but veratridine in the dog evokes reflex gastric and circulatory responses in anesthetized dogs. These responses are greater during stimulation of cardiac receptors in the inferoposterior wall. A similar reflex may contribute to the nausea and vomiting in the early stages of inferoposterior myocardial infarction.