Author + information
- John E. Madias, MD∗ ()
- ↵∗Division of Cardiology, Elmhurst Hospital Center, 79-01 Broadway, Elmhurst, New York 11373
Zusterzeel et al. (1) reported in the September 2, 2014, issue of the Journal on the predictive merits of QRS morphology and QRS duration (QRSd) following implementation of cardiac resynchronization therapy (CRT), analyzing 31,892 patients from the National Cardiovascular Data Registry (NCDR) Implantable Cardioverter-Defibrillator registry. They found that among patients with left bundle branch block (LBBB), mortality is lower in women than men, but this is not the case for patients with non-LBBB QRS morphologies, regardless of the QRSd. In both sexes, longer QRSd in the LBBB cohorts was associated with lower mortality for both men and women; women with LBBB and QRSd of 140 to 159 ms had a lower mortality than men with similar QRS morphology and QRSd, although this was not the case in patients with QRSd of ≥150 ms.
Women have shorter QRSd than men, and this has been often attributed to their smaller ventricles (1); however, there is another mechanism producing additional shortening of the QRSd, which is dependent on QRS amplitude (QRSa) and leads to an apparent shortening of the QRSd (2–4). Accordingly, if QRSd is corrected for the corresponding QRSa in the patients of the NCDR, the results might be different than reported herein. In addition, attributing the mortality improvement in patients receiving CRT only to the QRS morphology (i.e., LBBB) and the QRSd underemphasizes the issue of the effectiveness of the CRT, based on the appropriate positioning of the left ventricular (LV) epicardial pacing leads and the timing of the stimulation of the LV and right ventricle. Regarding the later, perhaps data on the CRT biventricular pacing-based QRSd (5), if available in the NCDR, may enhance the value of the authors’ contribution.
- American College of Cardiology Foundation