QRS complexes during left bundle branch block ( LBBB ) and CRT were analyzed in 375 patients with ejection fraction 35 % and New York Heart Association class III-IV ( Leiden study : n = 226 ) as well as in patients with ejection fraction 40 % and New York Heart Association class I-II ( REVERSE trial : n = 149 ) for predictors of 10 % reduction in left ventricular end-systolic volume at 6 months .