Author Affiliations: Pacing Defibrillator and Leads Branch, Division of Cardiovascular Devices, Office of Device Evaluation, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland.
Sipahi et al reported in their meta-analysis of 5 cardiac resynchronization therapy (CRT) trials that QRS duration was an important predictor of response to CRT.1 They concluded that patients with a QRS of 150 milliseconds (ms) or greater had a reduction in heart failure events, whereas those with a QRS less than 150 ms did not. Unfortunately, there was no analysis of QRS morphology, eg, type of bundle branch block. Although they proposed a future meta-analysis to further refine QRS duration cutoffs, they failed to mention that QRS morphology may be equally or more important than QRS duration.
Selzman K, Shein M. QRS Morphology Rather Than QRS Duration for Predicting CRT Response. Arch Intern Med. 2011;171(20):1861-1862. doi:10.1001/archinternmed.2011.516