Small Doses of Subcutaneous Heparin, Plasma Free-Fatty-Acids, and the Incidence of Ventricular Arrhythmias in Patients with Acute Myocardial Infarction

The frequency of deep vein thrombosis (DVT) diagnosed with the ¹²⁵I-fibrinogen technique in patients with acute myocardial infarction (AMI) has been found to be reduced frcm about 20% without anticoagulation to about 5% with warfarin or small doses of subcutaneous heparin.

A somewhat higher incidence of ventricular tachycardia in patients with AMI treated with small doses of subcutaneous heparin has been reported. A possible mechanism might be heparin-induced activation of lipoprotein lipase with consequent increase of plasma free-fatty-acids (FFA), which have been found to be arrhythmogenic in patients with AMI.

In the present prospective trial, 99 patients with AMI and a history of less than 12 hours were allocated at random to treatment with subcutaneous heparin 5000 IU twice daily, or warfarin. In a randomized subsample of 21 patients fasting FFA analyses were performed before and 2 hours after the administration of anticoagulants on day 1 and 2.

No measurable increase in FFA concentrations was demonstrated in the heparin-treated patients, in spite of a significant influence on the thrombin clotting time.

The frequency of ventricular arrhythmias as detected by continous tape recordings was equal in the two treatment groups.

It is concluded that subcutaneous heparin 5 000 IU every 12 hours seems to be a safe measures of prophylaxis against venous thromboembolic ccmplications in patients with AMI.