Usefulness of QRS duration to predict response to cardiac resynchronization therapy in patients with end-stage heart failure.

Despite current selection criteria, 20% to 30% of patients treated with cardiac resynchronization therapy (CRT) do not benefit. It has been suggested that QRS duration may not be the optimal criterion to select patients for CRT. The objective of this study was to systematically evaluate the predictive value of QRS duration for response to CRT in a large group of consecutive patients. A total of 242 patients with heart failure scheduled for implantation of a CRT device were studied. Selection criteria for CRT included moderate to severe heart failure (New York Heart Association classes III to IV), left ventricular ejection fraction (LVEF)<or=35%, and QRS duration>120 ms. Before CRT implantation, QRS duration and clinical status were assessed, and 2-dimensional echocardiography (LV volumes and LVEF) was performed. Clinical status and changes in LVEF and LV volumes were reassessed at 6-month follow-up. After 6 months of CRT, 68% of patients were classified as clinical responders (improvement of >or=1 grade in New York Heart Association class) and 60% as echocardiographic responders (decrease>10% in LV end-systolic volume). At baseline, no significant differences were observed in QRS duration between clinical responders and nonresponders and between echocardiographic responders and nonresponders. No significant relation was demonstrated between baseline QRS duration and improvement in clinical and echocardiographic variables at 6-month follow-up. In conclusion, baseline QRS duration is not predictive for clinical and echocardiographic responses to CRT at 6-month follow-up. Better predictors for CRT response are needed.