Burden of Ventricular Arrhythmias in Cardiac Resynchronization Therapy Defibrillation and Implantable Cardioverter-Defibrillator Recipients with Recovered Left Ventricular Ejection Fraction: The Additive Role of Speckle-Tracking Echocardiography

Abstract

Patients with heart failure undergoing cardiac resynchronization therapy with or without defibrillator function may exhibit recovery of left ventricular ejection fraction (LVEF) during follow-up. Mechanical dispersion (MD; the SD of time to peak longitudinal strain by two-dimensional speckle-tracking echocardiography) is a known predictor of life-threatening ventricular arrhythmias (VAs). Relationships among LVEF recovery, changes in MD, and incidence of VA are still not extensively investigated. In this retrospective study, recipients of cardiac resynchronization therapy defibrillation (n=183) or implantable cardioverter-defibrillators only (n=87) underwent conventional and speckle-tracking echocardiography, both at baseline and after 10 to 12months, and were followed clinically. Both a ≥10% increase in LVEF and a final LVEF > 35% defined echocardiographic response (EchoResp). Reduction in MD ≥10 msec defined MD response (MDResp). Risk for appropriate implantable cardioverter-defibrillator therapy for VAs was assessed using a multivariable Cox hazard model. The prevalence of EchoResp+ and MDResp+ was 39% and 46%, respectively. During follow-up (49.8±33.5months), 74 VA events occurred. The incidence rate (per 100 patient-years) of VAs was lowest in the EchoResp+/MDResp+group (1.66%; 95% CI, 0.69%-3.99%), highest in the EchoResp-/MDResp- group (12.8%; 95% CI, 9.53%-17.2%; P<.0001), and intermediate in the EchoResp-/MDResp+ (5.5%; 95% CI, 3.3%-9.4%) or EchoResp+/MDResp- (5.3%; 95% CI, 3.0%-9.4%) group. Multivariable analysis showed that higher MD at follow-up (>71.4 msec) was associated with VAs independent of whether final LVEF was below or above the guideline-reported cutoff of 35% (P<.05). Among ICD recipients, improvements in both left ventricular function and MD are associated with reduced risk for VAs. In patients whose follow-up LVEFs improved to >35%, risk for VAs, although substantially decreased, remained elevated in the presence of still elevated MD.