Cardiac resynchronization therapy improves myocardial conduction

Abstract

Background Cardiac resynchronization therapy (CRT) reverses left ventricular remodeling and improves left ventricular systolic function. However, little is known about whether CRT improves ventricular conduction. Objective To determine the relationship between CRT response and QRS narrowing. Methods The study included consecutive patients who underwent CRT with defibrillator (CRT‐D) implantation between January 2002 and December 2012 and had subsequent generator replacement (GR). At the time of GR, super‐responder was defined as those who had left ventricular ejection fraction (LVEF) of 50% or more; patients who had an LVEF of 36–49% with an increase of more than 5% were considered responders, and the others were nonresponders. All patients were assessed 6 months after CRT‐D implantation and at the time of GR. Results Of 114 study patients, 58 (50.9%) were nonresponders, 29 (25.4%) responders, and 27 (23.7%) super‐responders. QRS narrowing at 6 months was significant in super‐responders (175.4 ± 21.4 to 159.7 ± 20.7 ms, P = 0.001) and responders (169.0 ± 21.3 to 157.7 ± 17.6 ms, P = 0.008). At time of GR, only super‐responders had further QRS narrowing (159.7 ± 20.7 to 146.3 ± 19.2 ms, P < 0.001). QRS duration change after 6 months was independently associated with super‐response (hazard ratio: 1.20 for every 5 ms QRS duration narrowing; 95% confidence interval, 1.06–1.38; P = 0.005), and QRS narrowing of 10 ms or more was associated with lower risk of all‐cause mortality after GR. Conclusion Continuous QRS narrowing after CRT, as an electrical marker, is associated with a super‐response to CRT. Further QRS narrowing 6 months after CRT implantation was associated with lower risk of mortality after GR.

Association between electrical and mechanical remodeling after cardiac resynchronization therapy: systematic review and meta-analysis of observational studies

“…Reverse electrical remodeling can be also detectable in shortening of paced QRS duration during chronic CRT. Yang et al assessed changes of paced QRS during longtime follow-up and found that narrowing of paced QRS was significant in responders after 6 month of biventricular pacing and super-responders (defined as LVEF ≥ 50%) had a further reduction of paced QRS duration measured at time of generator replacement [41].…”