INTRODUCTION

Implantable cardioverter defibrillators (ICD) significantly reduce mortality in patients with left ventricular (LV) dysfunction. However, little is known of the predictors of appropriate device activation in the primary prevention population. The aim of the present study was to determine predictors of appropriate device therapy in patients receiving ICDs for primary prevention.

METHODS & RESULTS: One hundred twenty-six patients with a left ventricular ejection fraction (LVEF) of < 35% and no prior documented ventricular arrhythmias underwent ICD implantation. The ICD implanted was single chamber in 60 (48%), dual chamber in 10 (8%), and biventricular in 56 (44%) patients and programmed with a single ventricular fibrillation (VF) zone at >180 beats per minute. Mean age was 58 +/- 13 years and mean LVEF was 23 +/- 7%. Fifty-two percent had ischemic cardiomyopathy and 66% were New York Heart Association heart failure class II/III. During a mean follow-up period of 589 +/- 353 days, 17 (13%) patients received appropriate device therapy and three (4%) received inappropriate shocks. Appropriate ICD therapy was associated with reduced LVEF (mean 19.9% vs 23.7%, P = 0.02) and the patients were less likely to have received angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blockers (AIIRB) (65% vs 90%, P = 0.04). Multivariate analysis revealed lack of ACEI/AIIRB (odds ratio [OR]= 0.06, 95% confidence interval [CI]= 0.01-0.37, P = <0.01) and lower LVEF (OR = 0.88, 95% CI 0.79-0.98, P = 0.02) predicted appropriate device activation. There was no difference in transplant-free survival between the appropriate therapy and no/inappropriate therapy groups, LVEF <20% and LVEF >20% group, and lack of ACEI/AIIRB and ACEI/AIIRB group.

CONCLUSION

Appropriate device activation occurred in 13% of patients in a primary prevention population. LVEF and absence of ACEI/AIIRB predicted appropriate ICD therapy.