The QRS interval in patients treated with resynchronization therapy: which value

The electrocardiogram (ECG) was introduced into clinical practice more than 100 years ago and despite increased sophistication in diagnostic methods the 12-lead ECG remains an important refer- ence step in patient evaluation today. In heart failure (HF) patients, a simple 12-lead ECG provides important information that can be integrated with the clinical evaluation in order to predict patient outcome. In a cross-sectional analysis of HF patients, stratified according to New York Heart Association (NYHA) functional class, Stelbrink et al. 1 reported that a more advanced NYHA class is associated with a more pro- longed PR interval and a wider QRS interval. The relationship between ECG parameters and patient outcome was the subject of a series of longitudinal studies, 2,3 which provided evidence that a wide QRS interval is associated with a worse prognosis, independently of the degree of left ventricular dysfunction. 4,5 On the other hand, QRS duration is also an important predictor of the development of congestive HF. For this purpose, in a series of 351 patients who had undergone coronary artery bypass grafting, Biffi et al.6creported that the independent predictors of congestive HF at follow-up were diabetes, history of stroke, and also QRS duration. Specifically, in this study, 51% of patients with a QRS duration of 140 ms before surgery developed con- gestive HF at follow-up; whereas only 24% of patients with a QRS duration of ,140 ms developed congestive HF (P , 0.05