A comparison of outcomes for patients receiving implantable cardioverter defibrillators for primary vs secondary-prevention.

OBJECTIVE

Compare characteristics and outcomes of patients receiving implantable cardioverter defibrillators (ICDs) for primary vs secondary cardiac arrest prevention.

METHODS

Patients in this cohort study were identified from a prospectively collected ICD database from June 1999 to August 2003 and divided into groups based on whether they received their ICD for primary or secondary-prevention of cardiac arrest. Patient follow-up continued until August of 2006 and the occurrence of appropriate ICD shocks, inappropriate ICD shocks, and mortality were compared between groups.

RESULTS

Of the 437 patients, 80.8% were male, 70.3% had coronary disease, and the mean age was 65.7+/-13.1 years. At baseline, primary-prevention patients had lower left ventricular ejection fraction (LVEF), use of a single chamber device and utilization of beta blockers and antiarrhythmics while having a greater use of biventricular pacing as compared to secondary-prevention patients. Over the first 12 months after implantation, the primary-prevention group was 43.0% less likely to receive an appropriate shock for ventricular arrhythmias (P=0.002) and 34.2% less likely to have an appropriate shock over the entire follow-up period (P=0.018). The incidence of inappropriate ICD shocks over the first 12 months after implantation and over the entire follow-up period was similar between groups (P=0.900 and P=0.217, respectively) as was mortality (P=0.228 and P=0.757, respectively).

CONCLUSIONS

Primary-prevention patients are characteristically different in numerous ways from secondary-prevention patients, but despite having a greater risk of experiencing appropriate shocks, exhibit a similar risk of inappropriate shocks and mortality over an average follow-up time exceeding 41 months.