Amiodarone: correlation of early and late electrophysiologic studies with outcome

Twenty-nine patients with recurrent sustained ventricular tachycardia (VT) or cardiac arrest underwent baseline, early (after 2 weeks of therapy) and late (after 5 months, mean) electrophysiologic studies during oral amiodarone therapy. Inducible sustained VT was present in all patients at baseline study, in 21 of 22 at early and in 26 of 29 at late study. The cycle length of induced VT increased from 263 +/- 60 msec at baseline study to 305 +/- 58 msec at early follow-up study and to 318 +/- 64 msec at late study (p less than .05 = baseline vs late study). The ventricular effective refractory period increased from 237 +/- 22 msec at the baseline study to 253 +/- 26 msec at early and to 268 +/- 24 msec at late study (p less than 0.05 baseline vs early, baseline vs late and early vs late study). Twenty-four patients had no recurrent VT or cardiac arrest on amiodarone (group 1). Five patients had recurrent arrhythmia (group 2). In group 1, the ventricular effective refractory period increased by 39 +/- 19 msec, but in group 2 decreased by 4 +/- 27 from baseline to late follow-up study (p less than 0.05). Similarly, in group 1 the cycle length of induced VT increased by a mean of 75 +/- 56 msec but decreased in group 2 by a mean of 11 +/- 81 msec from baseline to late follow-up study (p less than 0.05). From the above findings we conclude: Chronic electrophysiologic effects of amiodarone are not completely manifest after 2 weeks of oral therapy.(ABSTRACT TRUNCATED AT 250 WORDS)