Amiodarone for control of sustained ventricular tachyarrhythmia: clinical and electrophysiologic effects in 51 patients.

We evaluated the electrophysiologic effects of amiodarone and its ability to control ventricular arrhythmia in a selected group of 51 patients with refractory sustained ventricular arrhythmia. Amiodarone in doses of 400 to 800 mg/day prolonged refractoriness in the atria, atrioventricular (AV) node, and ventricle as well as conduction through the AV node and His-Purkinje system. Although it had no effect on measurements of sinus nodal function (sinus nodal recovery time and sinoatrial conduction time), it prolonged the sinus cycle length and 2 patients required a permanent pacemaker for symptomatic sinus bradycardia. Amiodarone did not alter the ease of inducibility in any consistent manner, and only 5 of 43 patients (12%) who had inducible ventricular tachycardia before amiodarone therapy had none induced during amiodarone treatment. The clinical effectiveness of amiodarone could be evaluated in 46 patients followed up for 8.6 +/- 6 months (range 0.5 to 22). It provided effective therapy in 23 patients (50%), partly effective therapy in 13 (28%), and was ineffective in 10 (22%). Adverse effects were noted in 28 of 51 patients (55%), and in 11 of these (22%) the drug had to be discontinued because of adverse effects. We conclude that amiodarone is a useful agent for the treatment of refractory sustained ventricular arrhythmia. Its use should be reserved for patients with life-threatening sustained arrhythmia because of the significant incidence of adverse effects. Furthermore, good clinical response can be observed in patients receiving amiodarone in spite of continued inducibility.