[Electrophysiological effects of flecainide on stimulus-inducible ventricular tachycardia].

13 patients (54 +/- 11.8 years) with either spontaneously occurring ventricular tachycardia (N = 12) or recurrent syncope (n = 1) probably due to ventricular tachycardia were studied electrophysiologically. In all patients, ventricular tachycardia could be initiated by programmed right ventricular stimulation during the control study. Ventricular tachycardia was sustained in eleven patients and non-sustained in the remaining two. After several days of oral administration of flecainide (400 to 500 mg per day) sustained ventricular tachycardia could still be initiated in seven cases that had to be interrupted by overdrive stimulation in five cases, and by cardioversion in the remaining two. In six cases, short, self-terminating episodes of ventricular tachycardia were induced. In four patients, induction of ventricular tachycardia was unchanged or made easier, whereas in seven cases ventricular tachycardia was more difficult to induce (i.e. later during the step-like stimulation program). The mean rate of induced ventricular tachycardia decreased from 215 +/- 59.4/min (+/- S.D.) to 169 +/- 44.1/min during flecainide (p less than 0.025). The interval between the tachycardia-initiating beat and the first beat of tachycardia increased from 323 +/- 61.1 ms to 438 +/-148.3 ms (P less than 0.02). The effective refractory period of the right ventricle was prolonged from 240 +/- 20.5 ms t 279 +/- 37.3 ms (P less than 0.005). The plasma concentration of flecainide at the time of stimulation was 995 +/- 238 ng/ml. Thus, flecainide exerts a marked effect on the rate of induced ventricular tachycardia, whereas the mode of induction did not change considerably. The prophylactic effect of long-term therapy with flecainide in patients with recurrent ventricular tachycardia needs further studies.