Abstract 3519: Reverse Electrical Remodeling of the Native Conduction With Cardiac Resynchronization Therapy Predicts Freedom From Ventricular Tachyarrhythmias
Introduction. Anti- and proarrhythmic effects of cardiac resynchronization therapy (CRT) remain controversial. Evidence of reverse electrical remodeling of the native conduction with CRT has been recently demonstrated. We hypothesized that reverse electrical remodeling with CRT is associated with freedom from ventricular tachyarrhythmias (VT).
Methods. The width of native QRS was measured in lead II digital ECG before and at least 6 months after implantation of CRT-D device in 63 patients (mean age 66.3±13.9; 44 male [70%]) with ischemic (34 patients, 53%) or non-ischemic cardiomyopathy, left bundle branch block (LBBB) [42 patients, 67%] or nonspecific intraventricular conduction delay (21 patient, 33%), and NYHA class III–IV heart failure. Biventricular pacing was inhibited for 10 seconds during regular device clinic visit, to record native QRS. Narrowing of the native QRS duration for at least 10 ms was considered as a marker of reverse electrical remodeling. Patients were followed prospectively at least 12 months after assessment for electrical remodeling. Sustained VT that required appropriate ICD therapies and cardiovascular death served as endpoints for survival analysis.
Results. QRS duration among all patients did not change significantly 17±11 months after CRT-D implantation (149±24 before vs. 146±31 after CRT-D implantation, NS). Reverse electrical remodeling was observed in 19 (30%) patients, in whom QRS duration decreased by 28±11 ms with similar rate and QRS morphology. Native QRS duration did not change or increased by 9±16 ms in the other 44 patients (70%). Baseline mean EF was not different in patients with or without reverse electrical remodeling (23±8 vs. 25±10%, NS). During 21±5 months of follow-up 15 patients (24%) had VT events (CL 340±52 ms), and overall 8 patients (13%) died. No patient who demonstrated reverse electrical remodeling had VT events or died (p<0.001).
Conclusion. Reverse electrical remodeling of the native conduction with cardiac resynchronization therapy predicts freedom from ventricular tachyarrhythmias. We speculate that QRS narrowing is a marker of overall recovery of the arrhythmogenic substrate.