Implantable cardioverter-defibrillator patients who are upgraded and respond to cardiac resynchronization therapy have less ventricular arrhythmias compared with nonresponders.

OBJECTIVES: The purpose of this study was to evaluate the impact of upgrading implantable cardioverter-defibrillator (ICD) therapy to cardiac resynchronization therapy (CRT) combined with defibrillator (CRT-D) on the occurrence of ventricular arrhythmia (VA) and appropriate ICD therapies.

BACKGROUND: CRT has been shown to improve left ventricular (LV) systolic function and induce reverse LV remodeling. In addition, it has been hypothesized that CRT may reduce the incidence of VA.

METHODS: Heart failure patients receiving an upgrade from ICD to CRT-D were evaluated. Patients were considered responders to CRT if LV end-systolic volume reduced ≥15% at 6 months of follow-up. Episodes of VA, triggering device therapy (anti-tachycardia pacing and shocks) were recorded before and after upgrade for the overall population. In addition, these outcomes were compared between CRT responders and nonresponders during the follow-up period after CRT response was assessed.

RESULTS: One hundred fifteen patients (93 males [81%], age 65 ± 12 years) were evaluated during a mean follow-up of 54 ± 34 months before CRT-D upgrade and 37 ± 27 months after upgrade. In CRT responders (n = 70), the frequency of VA requiring appropriate device therapy demonstrated a trend toward a decrease from 0.51 ± 0.79 to 0.30 ± 0.59 per patient per year after CRT-D upgrade (p = 0.052). In CRT nonresponders (n = 45), the frequency of VA requiring appropriate device therapy significantly increased from 0.40 ± 0.69 to 1.21 ± 2.53 per patient per year after CRT-D upgrade (p = 0.014).

CONCLUSIONS: After upgrade from ICD to CRT-D, nonresponders to CRT showed a significant increase in VA burden requiring appropriate device therapy.