Predicting hyperresponse among pacemaker-dependent nonischemic cardiomyopathy patients upgraded to cardiac resynchronization.

INTRODUCTION: Right ventricular (RV) pacing engenders left ventricular (LV) dyssynchrony and may diminish LV systolic function, promote adverse cardiac remodeling, and foster heart failure (HF). This process may be reversible in some pacemaker-dependent patients upgraded to cardiac resynchronization therapy (CRT). We examined the clinical characteristics of pacemaker-dependent patients who exhibit hyperresponse (i.e., normalization of LV function) with CRT upgrade. METHODS AND
RESULTS: We identified 51 chronically RV-paced patients with no coronary artery disease, LV ejection fraction (EF) ≤ 35%, and severe HF symptoms who were upgraded to CRT-defibrillators (CRT-D). Echocardiograms were performed before and ≥6 months after CRT. Patients with follow-up LVEF ≥ 50% were deemed hyperresponders. Clinical outcomes of death, cardiac transplant, mechanical circulatory support, and HF hospitalizations were assessed. Fifteen patients were CRT hyperresponders; all demonstrated ≥15% relative LV end-systolic volume decrease. Hyperresponders had smaller baseline LV dimensions and shorter known cardiomyopathy duration than nonhyperresponders (P < 0.01). The best predictors of hyperresponse using receiver operating characteristic analysis were LV end-systolic dimension <48 mm (area under the curve [AUC] 0.92, P < 0.001), LV end-diastolic dimension <58 mm (AUC 0.86, P < 0.001), and cardiomyopathy duration <24 months (AUC 0.82, P < 0.001). No hyperresponders died, received a cardiac transplant, or required mechanical circulatory support during 42 ± 22 months follow-up, whereas 5 nonhyperresponders died, 2 underwent transplant, and 1 required an assist device (log rank P = 0.049).
CONCLUSION: Among chronically RV paced patients who are upgraded to CRT-D, smaller baseline LV dimensions and shorter known cardiomyopathy duration predict hyperresponse. Hyperresponders have excellent long-term survival.