Background: Previous studies have shown that cardiac resynchronization therapy (CRT) improves cardiac performance and decreases mortality and hospital admission rates. However, it is not yet clear which patients will benefit from the procedure the most. The purpose of the study was to identify the pre-implant characteristics that better predict which patients will have the best outcome after CRT.
Methods: In this observational study, 156 patients were studied with echocardiography and a 6-minute walking test at baseline and 12 months after CRT.
Results: After CRT, we observed an increase in left ventricular ejection fraction (+29.6%, P < .0001), a decrease in left ventricular end systolic volume (-26.4%, P < .0001), in the proportion of patients with grade 2-4 mitral regurgitation (from 47.1% to 34.0%, P = .002), and with NYHA functional class III-IV (from 83.2% to 11.6%, P < .0001), an increase in exercise tolerance (+31.1%, P < .0001). Sixty-two patients had a marked increase in left ventricular ejection fraction (> 10 units); the only independent predictor of a marked effect of CRT was the nonischemic etiology of heart failure. In patients with ischemic cardiomyopathy, the benefit on ejection fraction correlates inversely with the extension of the ischemic damage.
Conclusions: CRT improves left ventricular function and exercise tolerance in the long term. The nonischemic etiology of the cardiomyopathy is the only independent predictor of a marked effect of CRT; this is probably due to the absence of ischemic, nonviable scar tissue in these patients.