Normalization of left ventricular ejection fraction after cardiac resynchronization therapy also normalizes survival

Background Earlier studies in patients with reduced left ventricular ejection fraction (LVEF) ≤35% and prolonged QRS showed better survival outcomes with cardiac resynchronization therapy (CRT). Some patients respond dramatically to CRT by improving their LVEF to the normal range and are considered "super-responders." Our aim was to determine whether super-responders survival increases to levels comparable to the general population. We compared the survival of super-responders to the general population matched for age and sex. Methods Of 909 patients with CRT device implantation between September 1998 and July 2008, 814 patients had pre- and post-CRT echocardiogram. A total of 95 patients with LVEF ≥ 50% following CRT were classified as super-responders. For 92 super-responders, who had U.S. Social Security numbers, an age- and sex-matched example was selected from the Social Security Life Tables. An expected survival plot of the matched population was then compared to the actual survival of super-responders. Results Super-responders had comparable survival to the age-sex matched general population (P = 0.53), and Kaplan-Meier survival analysis in 92 patients showed that super-responders with CRT pacemakers had similar survival to those with CRT implantable cardioverter defibrillators (P = 0.77). Super-responders were more likely to be females (54% vs 25%, P < 0.001) and less likely to have significant coronary artery disease (62% vs 42%, P < 0.001). Conclusions Normalization of LVEF by CRT improves survival to levels comparable to the general population. This observation favors the concept that some CRT candidates have a cardiomyopathy likely generated by the conduction abnormality that is reversible through biventricular pacing.