Incidence and clinical significance of multiple consecutive, appropriate, high-energy discharges in patients with implanted cardioverter-defibrillators

Background Some patients with an automatic implantable cardioverter-defibrillator (ICD) suffer multiple appropriate, consecutive, high-energy discharges (MCDs) during follow-up. Such events might represent resistant ventricular arrhythmias and might have prognostic significance. Methods and Results Eighty consecutive patients with an ICD were followed up for up to 82 months (mean, 21 +/- 19 months). Thirty-eight patients had survived an out-of-hospital cardiac arrest and 42 had recurrent ventricular tachycardia. During follow-up, 16 patients had MCD (group A), 26 patients had episodes of single appropriate discharges (group B), and 38 patients had no appropriate discharges (group C). Group A patients had worse functional status (P=.001), lower left ventricular ejection fractions (LVEFs) (P=.001), and lower survival rates (log rank, P=.003) than the remaining two groups of patients. Cox analysis showed LVEF (P=.001) to be an independent predictor of MCD. Independent predictors of death or heart transplant were MCD (P=.001), female sex (P=.001), age(P=.001), history of cardiac arrest (P=.003), and functional status (P=.003). The only independent predictor of total mortality was female sex (P=.002). Independent predictors of cardiac death were MCD (P=.007) and female sex (P=.018). Independent predictors of arrhythmic death were age (P=.001), female sex (P=.02), and MCD (P=.023). Conclusions In patients with an ICD, the development of MCD is an independent predictor of cardiac and arrhythmic mortality. If this finding is confirmed in larger studies, it may help to identify patients in whom other therapeutic alternatives, ie, heart transplantation, should be considered during follow-up after ICD implantation.