Cardiac ischaemia induces vagally mediated lower oesophageal sphincter relaxation.

Gastro-oesophageal reflux and coronary artery disease frequently coexist. Direct stimulation of myocardial vagal receptors impairs lower oesophageal sphincter (LOS) function but the effect of cardiac ischaemia has not been examined. Eight adult mongrel dogs were studied under general anaesthesia. Each underwent occlusion of the left circumflex coronary artery before and after bilateral cervical vagotomy. Blood pressure, heart rate and LOS responses were measured. Median (range) LOS tone was significantly reduced by coronary artery occlusion, from 9 (6-14) to 6 (3-8) sphinctometer units (P < 0.01). This was accompanied by a reduction in heart rate (P < 0.05) and blood pressure (P < 0.01). After bilateral cervical vagotomy the same ischaemic insult produced no significant alteration in LOS tone or heart rate. These data suggest a direct vagal reflex to explain the high incidence of gastro-oesophageal reflux in patients with coronary artery disease.