[Effects of oral and injectable flecainide in patients with an accessory atrioventricular pathway].

Flecainide, a new Vaughan-Williams Class Ic anti-arrhythmic agent, was used in 21 patients with an accessory AV conduction pathway which was apparent in 16 cases (WPW syndrome), latent in 1 case and concealed in 4 cases (block in the anterograde direction). Seventeen patients had spontaneous and inducible arrhythmias; 13 supraventricular tachycardias (SVT) due to orthodromic reentry including the accessory AV pathway and 4 atrial arrhythmias. Intravenous flecainide (2 mg/kg over 5 minute period) terminated the 13 cases of SVT in an average of 3 minutes by depressing then blocking retrograde conduction in the accessory pathway and 3 out of 4 cases of atrial arrhythmias. Conduction in the accessory pathway was blocked in the anterograde direction in 75% of cases and depressed in the rest; it was blocked in the retrograde direction in about half the cases and depressed in the rest. Intravenous flecainide completely prevented the induction or arrhythmias in 13 out of 17 patients (76%). Oral flecainide blocked the accessory pathway in the anterograde direction in 68.7%, and in the retrograde direction in 62% of patients, and prevented arrhythmias during provocative testing in 82% of patients (14 out of 17). With an average follow-up of 20.7 +/- 2.6 months with oral doses adapted to body weight and to the response to IV flecainide only one recurrence of atrial fibrillation was observed, a 100% prevention of spontaneous SVT and 94% prevention of all arrhythmias (16 out of 17 cases). The predictive value for the response to oral therapy of the tests of regularisation of SVT by IV flecainide and of the tests of non-provocation of SVT with oral or IV flecainide was excellent (100%). The cardiac tolerance was very good in these 21 patients (17 of whom had no valvular or myocardial lesion). There were 6 minor cases of general intolerance to oral therapy which were not dose related, only 1 of which required interruption of therapy. Flecainide appears one of the best choices for the treatment of preexcitation syndromes and their related arrhythmias at the present time.