The magnitude of the bradycardia induced by face immersion in patients convalescing from myocardial infarction.

Twenty patients who had suffered myocardial infarction within the previous 3 to 13 days performed face immersion with breath-holding. The maximum reduction in heart rate was 17 +/- 9 beats-min--1 (mean +/- SD). When compared with 24 patients without evidence ischaemic heart disease, they behaved more like younger patients (22 +/- 6) than patients in the same age range (7 +/- 6). A greater vagal response for age after infarction may reflect persistent hypersensitivity of a reflex designed to protect the myocardium during cardiogenic shock.