Comparison of high-dose with low-dose subcutaneous heparin to prevent left ventricular mural thrombosis in patients with acute transmural anterior myocardial infarction.

We performed a double-blind randomized trial comparing high doses of subcutaneous heparin (12,500 units every 12 hours) with low doses (5000 units every 12 hours) for 10 days in the prevention of left ventricular mural thrombosis in 221 patients with acute anterior myocardial infarction. Left ventricular mural thrombosis was observed by two-dimensional echocardiography on the 10th day after infarction in 10 of 95 patients (11 percent) in the high-dose group and in 28 of 88 patients (32 percent) in the low-dose group (P = 0.0004). One patient in the high-dose group and four in the low-dose group had nonhemorrhagic strokes (P = 0.17). One patient in the low-dose group had a fatal pulmonary embolism. There was no difference in the frequency of hemorrhagic complications, which occurred in six patients in the high-dose group and four in the low-dose group. The mean (+/- SEM) plasma heparin concentration was 0.18 +/- 0.017 U per milliliter in the high-dose group and 0.01 +/- 0.005 U per milliliter in the low-dose group (P less than 0.0001). In the high-dose group, the mean plasma heparin concentration was 0.10 +/- 0.029 U per milliliter among patients with abnormal two-dimensional echocardiograms, as compared with 0.19 +/- 0.019 U per milliliter among patients with normal echocardiograms (P = 0.01). We conclude that heparin administered subcutaneously in a dosage of 12,500 units every 12 hours to patients with acute anterior transmural myocardial infarction is more effective than a lower dosage (5000 units every 12 hours) in preventing left ventricular mural thrombosis.

Randomized placebo-controlled trial of propafenone for treatment of atrial tachyarrhythmias after cardiac surgery.

Fourteen patients with atrial fibrillation or flutter and a ventricular rate of greater than or equal to 120 beats/min occurring after cardiac surgery entered a double-blind placebo-controlled conditional crossover trial of intravenous propafenone. Patients randomly received either propafenone (2 mg/kg body weight) or placebo during a 10 minute intravenous infusion. If 20 minutes after the initiation of this infusion there was no conversion to sinus rhythm, the patient received a second intravenous infusion over 10 minutes (either propafenone or placebo, whichever was not given first). The electrocardiogram was recorded continuously throughout the study. Fourteen patients received propafenone and 10 received placebo. No patient's rhythm converted to sinus rhythm after placebo. In six patients (43%) (p less than 0.001), the arrhythmia converted to sinus rhythm between 5 and 10 minutes after the end of the propafenone infusion. After propafenone, the ventricular response to atrial fibrillation or flutter decreased significantly from 141.6 +/- 15.2 to 116.0 +/- 15.5 beats/min. Ventricular rate did not change after placebo. The mean propafenone plasma concentration was 3.46 +/- 2.17 mg/liter. The only side effect of propafenone noted was a decrease in systolic blood pressure of 9 +/- 9 mm Hg. Propafenone was useful for management of atrial fibrillation after cardiac surgery both for control of rapid ventricular response and for conversion to sinus rhythm.