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Evidence for Electrical Remodeling of the Native Conduction System with Cardiac Resynchronization Therapy
Author(s) -
HENRIKSON CHARLES A.,
SPRAGG DAVID D.,
CHENG ALAN,
CAPPS MELISSA,
DEVAUGHN KATHLEEN,
MARINE JOSEPH E.,
CALKINS HUGH,
TOMASELLI GORDON F.,
BERGER RONALD D.
Publication year - 2007
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.2007.00717.x
Subject(s) - medicine , cardiac resynchronization therapy , cardiology , qrs complex , left bundle branch block , ejection fraction , heart failure , ischemic cardiomyopathy , bundle branch block , right bundle branch block , electrical conduction system of the heart , electrocardiography , qt interval
Background:Cardiac resynchronization therapy (CRT) improves hemodynamics and decreases heart failure symptoms. However, the potential of CRT to bring about electrical remodeling of the heart has not been investigated.Methods and Results:We studied 25 patients, of whom 17 had a nonischemic cardiomyopathy, and 8 had an ischemic cardiomyopathy; 16 had left bundle branch block (LBBB), 1 right bundle branch block (RBBB), and 8 nonspecific intraventricular conduction delay. During routine device clinic visits, patients with chronic biventricular pacing (>6 months) were reprogrammed to VVI 40 to allow for native conduction to resume. After 5 minutes of native rhythm, a surface electrocardiogram (ECG) was recorded, and then the previous device settings were restored. This ECG was compared to the preimplant ECG. Preimplant mean ejection fraction was 19% (range, 10%–35%), and follow‐up mean ejection fraction was 35% (12.5%–65%). Mean time from implant to follow‐up ECG was 14 months (range, 6–31). The QRS interval prior to CRT was 155 ± 29 ms, and shortened to 144 ± 31 ms (P = 0.0006), and the QRS axis shifted from −1 ± 59 to −26 ± 53 (P = 0.03). There was no significant change in PR or QTc interval, or in heart rate.Conclusion:CRT leads to a decrease in the surface QRS duration, without affecting other surface ECG parameters. The reduced electrical activation time may reflect changes in the specialized conduction system or in intramyocardial impulse transmission.