Effect of flecainide on left ventricular ejection fraction.

Antiarrhythmic agents may depress cardiac contractility and worsen heart failure. Flecainide is an effective antiarrhythmic drug, but when administered orally in patients with left ventricular (LV) dysfunction, its effect on LV function is unknown. To assess the effects of flecainide on cardiac function, LV ejection fraction (LVEF) was measured by radionuclide ventriculography in 36 patients with LV dysfunction (LVEF less than or equal to 40%), prior to, and 7 days after, drug therapy was initiated. To analyse the possibility of a dose-dependent effect on LVEF, 18 patients received 200 mg day-1 of flecainide and 18 patients with an identical initial LVEF (27 +/- 8 vs 27 +/- 9) (NS) received 300 mg day-1. The study was stopped in 7 patients because of severe cardiac adverse effects; in these patients the LVEF was significantly lower (15 +/- 7) than that of the 29 patients who completed the protocol (27 +/- 8) (P less than 0.01). In patients who completed the protocol, there was no significant change in LVEF either with a daily dosage of flecainide of 200 mg day-1 (27 +/- 8 vs 27 +/- 8) or with 300 mg day-1 (27 +/- 9 vs 28 +/- 13). Thus, in the patients with LV dysfunction studied, oral flecainide did not significantly affect LV function either with a low or with the usual daily dosage. However, in patients with severe impairment of LV function (LVEF less than 30%) flecainide must be used carefully owing to a higher incidence of adverse effects on cardiac rhythm.