Interaction of Left Ventricular Remodeling and Regional Dyssynchrony on Long-Term Prognosis after Cardiac Resynchronization Therapy

BACKGROUND: Left ventricular (LV) remodeling in heart failure (HF) manifested by chamber dilatation is associated with worse clinical outcomes. However, the impact of LV dilatation on the association of measures of dyssynchrony with long-term prognosis and resynchronization potential after cardiac resynchronization therapy (CRT) remains unclear.

METHODS: Two hundred sixty CRT patients in New York Heart Association classes II to IV, with ejection fractions ≤ 35% and QRS intervals ≥ 120 msec, were prospectively studied. Quantitative echocardiographic assessment of LV volumes and mechanical dyssynchrony by radial strain was conducted at both baseline and 6-month follow-up. Primary outcome events were predefined as death or HF hospitalization, and secondary outcome events were defined as all-cause death over the 4 years after CRT.

RESULTS: Patients were divided into two groups using the median of the baseline indexed LV end-diastolic volume (EDVI). Patients with less dilated left ventricles (EDVI < 90 mL/m(2)) had improved prognosis compared to those with severely dilated left ventricles (EDVI ≥ 90 mL/m(2)) for both primary (adjusted hazard ratio [HR], 2.20; 95% CI, 1.44-3.38; P < .01) and secondary (adjusted HR, 1.94; 95% CI, 1.21-3.11; P < .01) events. Similarly, reduction in baseline dyssynchrony was associated with good prognosis for both the primary (HR, 0.39; 95% CI, 0.23-0.68; P = .001) and secondary (HR, 0.41; 95% CI, 0.22-0.75; P = .004) events. A linear association was found between each 10% reduction in dyssynchrony and events (P < .01). Notably, patients with less dilated left ventricles had nearly fourfold more frequent improvement in dyssynchrony compared to those with severely dilated left ventricles (odds ratio, 4.10; 95% CI, 1.81-9.28; P < .01). No other baseline prognostic marker was associated with the resynchronization ability of CRT.

CONCLUSIONS: Patients with severe LV remodeling (EDVI ≥ 90 mL/m(2)) have a poor prognosis following CRT device implantation. This is most likely due to impaired resynchronization efficacy.