The results from EchoCRT fit well with the results of a meta-analysis that my associates and I recently ran on data from 3,782 heart failure patients treated with CRT in five trials sponsored by Medtronic. The results showed that QRS duration was a powerful predictor of the effects of CRT on morbidity and mortality.
The meta-analysis results confirmed the benefit of CRT in patients with mild, moderate, or severe heart failure symptoms, in sinus rhythm, and with a QRS duration of at least 140 msec, and in these patients CRT is standard of care. The results also showed that the benefits from CRT diminish as the QRS duration goes below 140 msec. Patients with a QRS duration of 130-139 msec are in a gray zone. If they need a defibrillator, then making it a CRT device makes sense, but if no device implant is planned then continued attempts at medical treatment are probably better than going to CRT.
I would avoid CRT in patients with a QRS of less than 130 msec, and now the EchoCRT results show evidence of harm in these patients. A lot of patients with a QRS duration of 120-129 msec have been receiving CRT devices when the chances of benefit are small. This might be a treatment of last resort, but only when you have exhausted all the other treatment alternatives.
The meta-analysis also showed that QRS duration was the only independent predictor of CRT outcomes (Eur. Heart J. 2013 [doi:10.1093/eurheartj/eht290]). QRS morphology – whether or not there is a left bundle branch block – was not a significant factor relative to QRS duration. The EchoCRT results also showed that echocardiography used to diagnose left-ventricular dyssynchrony failed to identify a subgroup of patients with a narrow QRS duration who benefited from CRT.
Dr. John G.F. Cleland is professor of medicine at the University of Hull (England). He has been a consultant to Biotronik, St. Jude, and Medtronic. He made these comments in an interview.
