Relationship of baseline electrocardiographic characteristics with the response to cardiac resynchronization therapy for heart failure

Prospective identification of patients most and least likely to respond to cardic resynchronization the-ropy (CRT) for congestive heart failure (CHF) will allow clinicians to target this intervention most efficiently. The authors hypothesized that EGG variables including RBBB and indicators of RV dysfunction and extensive prior myocardial infarction would correlate with diminished response to CRT This study analyzed preimplantotion ECGs in 110 patients with ICD indications and CHF due to left ventriculor systolic dysfunction randomized to active biventricular pacing in the MIRACLE ICD trial. Clinical and ECG variables on the outcome of change in peak oxygen consumption from baseline to 6 months (Delta-VO2) were evaluated. For this cohrt, average peak VO2 improved from 13.4 to 14.3 mL/kg per minute. Among clinical variables, the strongest predictors Of increasing Delta-VO2 were reduced exercise time and peak V02 at baseline. A dominant R wave in lead a VR, RBBB, and evidence of prior anterior inforction were each associated with significantly smaller average improvements in Delta-VO2 than their absence in univoriate analysis. Alternative EGG criteria, including QRS duration, had no relationship with the outcome. In a multivoriote model, only baseline VO2 (beta = -0.3, P = 0.001) and EGG evidence ofp-rior anterior infurction ( beta = - 1.3, P = 0.03) were associated with the outcome. EGG markers of anterior inforction and RV dilation mayhelp identify CHFpatients unlikely to benefitfrom biventricular pacing. Further assessment is needed of these and other predictors of therapeutic response to CRT