Reverse electrical remodeling by cardiac resynchronization therapy: prevalence and clinical impact.
BACKGROUND
Cardiac resynchronization therapy (CRT) improves left ventricular ejection fraction (LVEF) in patients with congestive heart failure, LV systolic dysfunction, and a wide QRS complex. Previous reports suggest that CRT may also induce electrical remodeling but the impact on clinical outcome remains unknown.


OBJECTIVE
We sought to determine (1) if chronic CRT induces a relevant shortening of the intrinsic QRS (iQRS), (2) whether changes in the native conduction system correlate with clinical or echocardiographic response to CRT, and (3) to identify predictors of iQRS width shortening.


METHODS
We prospectively included 85 consecutive patients with left bundle-branch block who received a CRT device in 3 French centers. NYHA class, iQRS duration, LVEF, and left ventricular volumes were assessed before and 1 year after CRT implantation. Clinical and echocardiographic CRT responders were defined respectively as NYHA class improvement >1 class without heart failure hospitalization and an increase of LVEF by ≥10% and/or a decrease in LVESV by ≥15%. Electrocardiographic responders were defined as a decrease in iQRS duration by ≥20 ms.


RESULTS
Baseline and 1-year follow-up mean iQRS durations were, respectively, 168.0 ± 19.7 ms and 149.6 ± 31.6 ms (P < 0.0001). Electrocardiographic response, observed in 43/85 patients (51%), was associated with a greater rate of clinical (P = 0.035) and echocardiographic (P = 0.023) response. Younger age, male gender, and longer baseline QRS width were independent predictors of electrocardiographic response.


CONCLUSIONS
CRT decreases iQRS duration. A reduction of at least 20 ms in iQRS duration is associated with better clinical and echocardiographic response.
INSERM U642, Rennes, France Université de Rennes 1, LTSI, Rennes, France.
Frederic A
FA
Sebag
Raphael P
RP
Martins
Pascal
P
Defaye
Françoise
F
Hidden-Lucet
Philippe
P
Mabo
Jean-Claude
JC
Daubert
Christophe
C
Leclercq
D000200:Action Potentials; D000368:Aged; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy; D016009:Chi-Square Distribution; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D005602:France; D006329:Heart Conduction System / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011446:Prospective Studies; D020127:Recovery of Function; D013318:Stroke Volume; D013997:Time Factors; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D016277:Ventricular Function, Left; D020257:Ventricular Remodeling