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 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 fraction 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 RESULTS

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 less than 0.001), a fall in stroke work index from 26 to 18 g.m/m2 (mean change 8 +/- 2; P less than 0.001), and an increase in left ventricular filling pressure from 19 to 22 mm Hg (mean change 3 +/- 2; P less than 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.