Influence of prophylactic furosemide on arrhythmias in acute myocardial infarction--a controlled study.

In a prospective controlled study the frequency of arrhythmias during the early phase of acute myocardial infarction (AMI) was evaluated in 73 consecutive patients randomly assigned to either high or low dose furosemide prophylaxis. The high dose group (HDG) received 120 mg and the low dose group (LDG) 20 mg furosemide i.v. during the initial 24 hours in hospital. Increased diuresis, haemoconcentration and augmented heart rates were found in the HDG. No electrolyte disorders separated the groups. Hypokalemia was seen in two HDG patients and in one LDG patient on admission, and in two and three patients respectively after 24 hours. Continuous ECG recordings at a paper speed of 10 mm s-1 were obtained from all patients. Two patients in the HDG had ventricular fibrillation, none in the LDG. The number of patients with various arrhythmias was not significantly different in the two groups. Supraventricular tachyarrhythmias were more common in the HDG, whereas ventricular tachycardia and ventricular extrasystoles were seen more often in the LDG. We conclude that heart rate and recurrence of tachyarrhythmias in AMI may be influenced by furosemide therapy, seemingly through mechanisms other than electrolyte imbalance.