Influence of left ventricular dysfunction on flecainide therapy.

Seventy-six patients with ventricular tachyarrhythmias (40 sustained and 36 nonsustained) were treated with oral flecainide. Radionuclide left ventricular ejection fraction was 30% or less in 33 patients and greater than 30% in 43 patients. Before flecainide, compensated heart failure was present in 23 patients (ejection fraction less than or equal to 30% in 15 and greater than 30% in 8). Flecainide mean dose was 150 mg twice daily and mean plasma concentration was 720 ng/ml. New or worsened congestive heart failure occurred in seven patients on flecainide therapy, all with an ejection fraction of less than 30%; six had a previous history of compensated heart failure and of these, three died. Ejection fraction was the only independent variable that significantly influenced efficacy and tolerance of flecainide. After 1 year of therapy, efficacy and tolerance was 58% (25 of 43) in patients with an ejection fraction greater than 30% and 12% (4 of 33) in patients with an ejection fraction of 30% or less (p less than 0.001). Thus, congestive heart failure can occur during flecainide therapy, particularly in patients with a previous history of congestive heart failure and ejection fraction of less than 30%, and may particularly limit therapy in these patients. Clinical efficacy and tolerance were significantly lower in patients with an ejection fraction of less than 30%.