Effects of intravenous nitroglycerin on ventricular ectopic beats in acute myocardial infarction.

Ventricular premature beats (VPBs) in 21 consecutive patients with acute myocardial infarction (AMI) were continuously recorded on magnetic tape by means of an automatic arrhythmia monitor and counted manually. The patients were sequentially assigned to either a control (n = 11) or nitroglycerin group (n = 10). Both groups were comparable for age as well as for onset, localization, and extension of infarction. Recording in the control groups was begun at a mean of 9.3 hours following onset of infarction as obtained from patient history. This interval was 12.0 hours in the nitroglycerin group. At the start of therapy, the number of VPBs was identical in both groups. Ten patients received a mean of 2.1 mg of nitroglycerin per hour intravenously for 48 hours, whereas the control group received no specific therapy. The number of VPBs in the control group increased progressively until the sixth hour of registration and reached a maximum of 165% of the baseline value before subsequently declining. Nitroglycerin administration was associated with a significantly more rapid reduction in ventricular arrhythmias: 6 hours after onset of recording, the number of VPBs had declined to 39% of the baseline value (p less than 0.05 compared to control group). This study demonstrates that nitroglycerin reduces ventricular ectopic beats in the acute phase of myocardial infarction.