EFFICACY AND SAFETY OF COMBINATION THERAPY WITH AMIODARONE AND TYPE-IAGENTS FOR TREATMENT OF INDUCIBLE VENTRICULAR-TACHYCARDIA

In a prospective study the efficacy of amiodarone in combination with the three Class I drugs mexiletine, flecainide, or encainide was evalu ated consecutively in 12 patients with recurrent ventricular tachycard ias (VT) by programmed stimulation. None of the tested drug combinatio ns suppressed induction of sustained VT. The combination of amiodarone with Class IC drugs flecainide and encainide prolonged the cycle leng th of VT significantly, whereas the combination with mexiletine did no t have the same degree of slowing on the VT cycle length. Several proa rrhythmic effects occurred during the combination therapy with encaini de: (1) frequent, spontaneous recurrences of hemodynamically well tole rated VT in four patients; (2) enhanced inducibility of VT in three pa tients; (3) impaired termination of VT in three patients. Though a mar ked increase in QRS and QTc intervals was observed by combined treatme nt with encainide, no significant correlation could be established bet ween aggravation of arrhythmia and plasma levels of encainide, degree of QRS widening, JT or QTc prolongation. The only predictor for the oc currence of proarrhythmic events was found in left ventricular ejectio n fraction. These findings suggest that in patients refractory to amio darone alone or a combination with mexiletine, the combined treatment of amiodarone with other Class IC drugs prolongs the VT cycle length b ut does not suppress induction of VT during programmed stimulation. Co mbination therapy of amiodarone with encainide was associated with a h igh incidence of proarrhythmic effects.