Vectorcardiographic QRS area is associated with long-term outcome after cardiac resynchronization therapy

BACKGROUND Recent studies have suggested that vectorcardiographic measures predict left ventricular (LV) reverse remodeling and clinical outcome in patients receiving cardiac resynchronization therapy (CRT). OBJECTIVES The objectives of this study were to compare predictive abilities of different vectorcardiographic measures (QRS area and sum absolute QRS-T integral) and transformation methods (Kors and inverse Dower) and to assess the independent association between the best predictor and outcomes in CRT recipients. METHODS This retrospective study included CRT recipients with a digital baseline electrocardiogram, QRS duration >= 120 ms, and ejection fraction <= 35%. The end point was a composite of heart transplantation, LV assist device implantation, or all-cause death. Analyses were performed for the overall cohort and for a prespeci-fied subgroup of patients with left bundle branch block (LBBB). RESULTS Of 705 included patients with a mean age of 66.6 +/- 11.5 years, 492 (70%) were men, 374 (53%) had ischemic heart disease, and 465 (66%) had LBBB. QRS area from vectorcardiograms derived via the Kors transformation demonstrated the best predictive value. In multivariable Cox regression, patients with a smaller QRS area (<= 95 mu Vs) had an increased hazard in the overall cohort (adjusted hazard ratio 1.65; 95% CI 1.25-2.18 P<.001) and in the LBBB subgroup (adjusted hazard ratio 1.95; 95% CI 1.38-2.76 P<.001). QRS area was associated with outcome in patients with QRS duration,150 ms (unadjusted hazard ratio 3.85; 95% CI 2.02-7.37 P<.001) and in patients with QRS duration >= 150 ms (unadjusted hazard ratio 1.76; 95% CI 1.32-2.34 P<.001). CONCLUSION Vectorcardiographic QRS area is associated with survival free from heart transplantation and LV assist device implantation in CRT recipients.