Adverse hemodynamic and clinical effects of encainide in severe chronic heart failure

Study Objective: To evaluate the hemodynamic effects of the antiarrhythmic drug, encainide, in the patients with severe chronic heart failure. Design: Unblinded, before-after study. Setting: Referral center for patients with heart failure. Patients: Thirty patients with severe chronic heart failure and a left ventricular ejection less than 40%. Interventions: Invasive hemodynamic measurements were done (using a balloon-tipped thermodilution catheter) before and for 3 hours after a single oral dose of 50 mg of encainide. Measurements and Main Result: Ninety to one hundred and twenty minutes after its administration, encainide produced a significant deterioration in cardiac performance, as reflected by a fall in cardiac index from 2.3 to 1.8 L/min · m² body surface (mean change 0.5 ± 0.1; P < 0.001), a fall in stroke work index from 26 to 18 g-m/m² (mean change 8 ± 2; P < 0.001), and an increase in left ventricular filling pressure from 19 to 22 mm Hg (mean change 3 ± 2; P < 0.05). These deleterious hemodynamic effects were accompanied by worsening symptoms of heart failure in 8 of the 30 patients. Serum levels of encainide and its metabolites, O-desmethylencainide and 3-methoxy-O-desmethylencainide, were within the therapeutic range in most patients. Conclusions: Encainide can cause adverse hemodynamic and clinical effects in patients with severe chronic heart failure.