Rethinking QRS Duration as an Indication for CRT

Abstract

Cardiac resynchronization therapy (CRT), radiofrequency ablation for atrial fibrillation,1,2 and the invasive management of ventricular tachycardia are likely the 3 major changes that have impacted cardiac electrophysiology practice over the last 2 decades. Of these, the literature basis for CRT use is by far the strongest, and the evidence is such that the potential for benefit from left ventricular pacing for drug refractory heart failure (HF) patients is beyond question.3-5 Several major and fundamental challenges remain in terms of optimizing CRT benefit and particularly with preprocedural identification of patients most likely to benefit from this therapy. Following the course of various contentions in terms of ideal method of selecting patients,6,7 including echocardiographic parameters for mechanical dyssynchrony, has been a veritable rollercoaster ride with initial promise followed by the absence of verifiable utility in larger well-conducted studies.8 From the very earliest discussion on CRT, QRS duration was recognized as a potentially simple and intuitive variable that could guide patient selection and subsequent device optimization. However, it was quickly recognized that this parameter may be simplistic and evidence for its utility, particularly for patient selection, not forthcoming.9,10 In this issue of the Journal of Cardiovascular Electrophysiology, Stavrakis et al.11 present important findings from a well-conducted meta-analysis of 5 trials (COMPANION,12 CARE-HF,13 REVERSE,14 MADIT CRT,15 and RAFT5), specifically with regard to QRS duration and CRT benefits. In this meticulously conducted and clearly written manuscript, the authors present important evidence for their potentially practice-impacting conclusion that CRT should not be routinely considered for patients with QRS duration <150 ms. Before the readers and practitioners of electrophysiology and HF management decide on whether we rethink one of our primary indications for CRT (QRS duration ≥120 ms), it is worthwhile to examine from cardiac electrophysiology why and why not QRS duration should impact or may impact CRT benefit.