Acute hemodynamic effects of intravenous encainide in patients with heart disease

Encainide, a new antiarrhythmic drug, was given intravenously (0.9 mg/kg) to 18 patients over 15 minutes to evaluate the hemodynamic effects. Hemodynamics and drug plasma concentrations were measured during and 30 minutes postdrug infusions. Encainide infusion was associated with a decrease in cardiac index from 2.6 +/- 0.7 to 2.4 +/- 0.7 L/min/m2 (p less than .05), a significant decrease in stroke work index and left ventricular end-diastolic pressure, and with a rise in systemic vascular resistance. There was no change in systemic or pulmonary arterial pressure, left ventricular dp/dt, or pulmonary vascular resistance. The patients were studied 30 to 60 minutes after cardiac angiography. Comparison of hemodynamic values obtained preangiography with those obtained postangiography (before, during, and after drug infusion) strongly suggests that many of the observed effects were due to radiographic contrast media (initial osmotic volume loading and subsequent diuresis). We conclude that if encainide has any significant hemodynamic effects after intravenous use, it is a modest decrease in cardiac output, possibly as a result of decreased left ventricular filling pressure.