Correlation of Electrical and Mechanical Reverse Remodeling after Cardiac Resynchronization Therapy

Abstract

Cardiac resynchronization therapy (CRT) improves clinical outcome in many patients with refractory heart failure (HF). This study examined whether CRT is associated with reverse electrical remodeling by surface electrocardiogram (ECG). Consecutive CRT recipients at the University of Pittsburgh Medical Center with >90 days of follow-up were included in this analysis. ECG data were abstracted from medical records. Subjects with a relative increase of > or =15% in left ventricular ejection fraction (LVEF) after CRT were considered responders. A total of 113 patients (age 69 +/- 11 years, men 70%, white 92%) were followed for a mean duration of 407 +/- 290 (92-1439) days. Overall, LVEF increased after CRT (29 +/- 13% vs 24 +/- 9%; P < 0.01) and 50% of patients were responders. The mean native QRS interval among responders was higher than in nonresponders (163 +/- 32 ms vs 148 +/- 29 ms; P < 0.01). More than 3 months after CRT, there was no change in the paced QRS duration compared to baseline. Paced QRS duration, however, decreased among responders and increased among nonresponders and was significantly different by response status (P < 0.001). There was a significant correlation between increase in LVEF and decrease in paced QRS width in the overall population (r =-0.3; P < 0.01). Among responders to CRT, the paced QRS width decreases significantly, whereas it increases among nonresponders. Given the paced nature of the QRS, the improved conduction probably reflects enhanced cell-to-cell coupling after CRT as opposed to improved conduction within the His-Purkinje system. These findings have significant implications as to the mechanisms of benefit from CRT.