Prognostic value of the changes in the mode of ventricular tachycardia induction during therapy with amiodarone or amiodarone and a class 1A antiarrhythmic agent

The prognostic value of 3 previously reported programmed stimulation efficacy criteria was studied in 70 patients taking amiodarone for sustained ventricular tachycardia (VT). At baseline all patients had VT inducible by programmed stimulation. After amiodarone loading (935 ± 271 mg/day for 16 ± 7 days), efficacy of amiodarone was determined by 3 programmed stimulation criteria (criterion I = VT not inducible or 15 beats or less; criterion II = VT not inducible or harder to induce; criterion III = VT not easier to induce). Amiodarone was effective in 12, 25 and 49 of 70 patients by criteria I, II and III, respectively. There were 16 recurrences or cardiac arrest during the follow-up period (19 ± 19 months). Actuarial arrhythmia-free survival rates at 1 and 2 years were: 90% and 90% in patients with efficacy by criterion I and 78% and 78% in patients with inefficacy, respectively; 84 % and 84% in patients with efficacy by criterion II and 78% and 78% in patients with inefficacy, respectively; and 80% and 80% in patients with efficacy by criterion III and 79% and 79% in patients with inefficacy, respectively (difference not significant for all). From the results of follow-up at 2 years, sensitivities of criteria I, II and III were 92%, 75% and 33%, respectively. Specificities were 17%, 26% and 70%, respectively, and predictive accuracies were 43%, 43% and 67%, respectively. Thus, patients with efficacy by criterion I appear to have a better prognosis when compared with patients with inefficacy. However, many patients with inefficacy by criterion I had a good outcome (nonspecificity). Criteria II and III based on the changes in the mode of VT induction may not predict clinical outcomes. Criterion II is sensitive but nonspecific and criterion III is specific but insensitive.