FLECAINIDE-INDUCED INCREASE IN QRS DURATION AND PROARRHYTHMIA DURING EXERCISE

In patients taking flecainide, exercise-induced arrhythmias are believ ed to be related to QRS widening at rest and during exercise. Out aim was to determine, retrospectively, predictive factors of flecainide-in duced (a) QRS widening at rest and during exercise, and (b) proarrhyth mia (PA) during exercise. Flecainide was administered to 119 patients for atrial and/or ventricular arrhythmias who performed a maximal trea dmill test. A total of 63 patients had a normal heart (defined by the absence of structural heart disease and an ejection fraction greater t han or equal to 55% by echocardiography and/or cardiac catheterisation ), 26 had coronaropathy, 18 valvulopathy and 3 had both, and 7 had dil ated and 2 hypertrophic cardiomyopathy. The mean dosage of flecainide was 190 or 200 +/- 10 mg/day. Previous myocardial infarction (MI) was a predictive variable of flecainide-induced QRS widening at rest (p = 0.04). During exercise, the risk factors of QRS widening were previous MI (p = 0.008), angina without previous MI (p = 0.009), structural he art disease (p = 0.001) and a bundle branch block at rest (p = 0.01). PA or exercise occurred in 7 patients. Structural heart disease (p = 0 .04) and an impaired left ventricular ejection fraction (LVEF) [p = 0. 02] were predictive variables of PA. AII patients with left ventricula r dysfunction and PA had a QRS widening with flecainide at rest greate r than or equal to 25%. The risk factors of QRS widening at rest and d uring exercise with flecainide were distinct from those of PA on exerc ise. In patients with an impaired LVEF, a flecainide-induced QRS widen ing of 25% at rest was the threshold value beyond which there was a hi gh risk of PA during exercise. This study was retrospective and not a double-blind trial, therefore the results need to be corroborated in a prospectively designed trial.