Bradycardia and its complications in the prehospital phase of acute myocardial infarction

Abstract

To elucidate the mechanisms of sudden death in the prehospital phase of acute myocardial infarction, the records of 84 patients with acute myocardial infarction transported by the mobile coronary care unit of Montgomery County, Maryland, were studied. Twenty patients (24 percent) had bradycardia, 10 receiving no pharmacologic therapy other than narcotic drugs. All 20 survived transportation and hospitalization, whereas 7 of the 64 patients without bradycardia died. Ten (12 percent) had systolic blood pressure values of 90 mm Hg or less, and bradycardia was an associated finding in five. Thus, in a suburban-metropolitan population of the United States, bradycardia occurs frequently during the prehospital phase of acute myocardial infarction. Although the overall incidence of hypotension is low by the time a patient calls for medical aid, hypotension is not uncommon in patients with bradycardia. The therapeutic implications of these observations depend on an elucidation of the natural history of acute myocardial infarction with bradycardia in the presence and absence of hypotension.