Amiodarone: Risk factors for recurrence of symptomatic ventricular tachycardia identified at electrophysiologic study

Ventricular tachycardia induced by programmed electrical stimulation during amiodarone therapy often does not preclude a good clinical response. The purpose of this study was to determine whether use of discriminant analysis could distinguish patients who remained asymptomatic from those who subsequently developed symptomatic ventricular tachycardia or cardiac arrest. Studies were performed in 37 patients with sustained ventricular tachycardia who still had ventricular tachycardia induced during programmed electrical stimulation during amiodarone therapy. The mean follow-up time was 14.1 ± 1.3 months (± SEM). Twenty-three patients remained asymptomatic, whereas 14 patients had symptomatic recurrence of their ventricular tachycardia. In patients with recurrence of arrhythmia compared with asymptomatic patients, administration of amiodarone caused a longer ventricular effective refractory period (296 ± 8 versus 271 ± 7 ms, p < 0.05) and a greater change in corrected QT [QT_c] interval (90 ± 18 versus 44 ± 9 ms, p < 0.02), but no difference in the decrease in premature ventricular complexes after treatment with amiodarone. During amiodarone therapy, nonbundle branch reentrant repetitive ventricular responses were induced by a single ventricular extrastimulus during sinus rhythm in 9 of 14 patients with recurrent arrhythmias compared with 2 of 21 asymptomatic patients (p = 0.001). Also, less aggressive pacing techniques were required to induce ventricular tachycardia in 9 of 14 symptomatic patients compared with 4 of 23 asymptomatic patients (p < 0.02). A discriminant analysis using the presence of nonbundle branch reentrant repetitive ventricular responses, change in method of ventricular tachycardia induction and either the change in QT_c interval or ventricular effective refractory period correctly identified clinical outcome in 90% of the patients, and all patients with recurrent arrhythmias were classified correctly. It is concluded that electrophysiologic testing during amiodarone therapy can provide data that identify patients who appear to be at risk for development of ventricular tachycardia after hospital discharge.