Impact of Degree of Left Ventricular Remodeling on Clinical Outcomes From Cardiac Resynchronization Therapy

Objectives: This study tested the hypothesis that the extent of left ventricular (LV) eccentric structural remodeling in heart failure with reduced ejection fraction (HFrEF) is directly associated with clinical event responses to cardiac resynchronization therapy (CRT). Background: Whether the severity of LV structural remodeling influences CRT treatment effects is unknown. Methods: COMPANION (Comparison of Medical Therapy, Pacing and Defibrillation in Heart Failure) trial data were analyzed retrospectively. Left ventricular internal dimensions at end diastole indexed by body surface area (LVEDDI) were measured pre-randomization by 2-dimensional echocardiography. LVEDDI values were stratified around the median value of 35 mm/m ² , and CRT (including CRT-P [CRT with only pacing capability] and/or CRT-D [CRT with an implantable defibrillator]) treatment effects were assessed and compared by LVEDDI group. Patients assigned to these treatments were compared to those undergoing optimal pharmacologic therapy (OPT) for the outcomes of all-cause mortality (ACM) or ACM and heart-failure hospitalization (ACM/HFH). Results: In the LVEDDI ≥35 mm/m ² group (n = 614), CRT vs. OPT was associated with a lower ACM/HFH hazard ratio (HR) (HR: 0.53; 95% confidence interval [CI]: 0.40 to 0.70; p <0.001), whereas in the LVEDDI <35 mm/m ² group, the CRT vs. OPT ACM/HFH hazard ratio was not statistically significant (HR: 0.80; 95% CI: 0.59 to 1.08; p = 0.15). For ACM alone, in the LVEDDI ≥35 mm/m ² group, the hazard ratio for CRT-P was 0.59 (95% CI: 0.39 to 0.90; p = 0.012) and for CRT-D 0.50 (95% CI: 0.32 to 0.77; p = 0.002). Neither of the CRT groups showed a statistically significant reduction in ACM in the LVEDDI <35 mm/m ² group. Conclusions: Larger versus smaller LVEDDIs are associated with a reduction in ACM with CRT-P or CRT-D treatment, and with a more effective reduction in ACM/HFH for the combined CRT treatment groups.