Extraordinarily Favorable Left Ventricular Reverse Remodeling through Long‐Term Cardiac Resynchronization: Super‐Response to Cardiac Resynchronization

BACKGROUND: Some chronic heart failure (CHF) patients show remarkable improvement in left ventricular (LV) remodeling after cardiac resynchronization therapy (CRT), for unclear reasons. This study aimed at identifying predictors of an extraordinarily favorable response to CRT. METHODS: We studied 136 CRT patients (104 men, median 66 years, QRS 162 ms, left ventricular ejection fraction 24 ± 7%, 70% coronary disease, all left bundle branch block [LBBB]). We measured LV end diastolic diameter (LVEDD) before and after long-term (9.4 ± 6.3 months) CRT. At baseline, LV pre-ejection interval (LVPEI), interventricular mechanical delay (IVMD), LV dyssynchrony (standard deviation of electromechanical delays [SDEMD] in eight LV segments), exercise capacity (pVO(2)), and ventilatory efficiency (VE/VCO(2)) were assessed. Patients with a LVEDD reduction beyond the 80th percentile (high responders [HR]) were compared to low responders (LR). RESULTS: In the HR group (n = 22), LVEDD was reduced from 71 to 52 mm (LR 64-61 mm, P < 0.001). HR had predominantly nonischemic heart disease (HR: 72%, LR: 44%, P = 0.019), tended to have a wider QRS (HR: 178 ms, LR: 162 ms, P = 0.066), had a longer LVPEI (HR: 179 ms, LR: 155 ms, P = 0.004), wider IVMD (HR: 60 ms, LR 48 ms, P = 0.05), larger LVEDD (P = 0.002), higher SDEMD (HR: 69 ms, LR: 46 ms, P = 0.044), but higher pVO(2) (HR: 17.5 mL/min/kg, LR: 13.5 mL/kg/min, P = 0.025) and lower VE/VCO(2) (HR: 31, LR: 35, P = 0.043), all compared to LR patients. CONCLUSION: Extraordinarily favorable reverse LV remodeling through CRT in CHF and LBBB appears to require a particularly dilated LV due to nonischemic heart disease with pronounced electromechanical alteration, but with a fairly preserved functional capacity before CRT.