Effect of lateral wall scar on reverse remodeling with cardiac resynchronization therapy.

BACKGROUND: Up to 50% of patients do not respond to cardiac resynchronization therapy (CRT). Recent work has focused on quantifying left ventricular (LV) scar, with conflicting results. Some studies have shown that the global extent of LV scar is important, whereas others found the size of the septal or lateral wall scar to be key. OBJECTIVE: This study sought to examine the relative importance of the size and distribution of LV scar in determining reverse remodeling to CRT. METHODS: Forty-nine patients had pre-implantation rubidium-82 and fluorine-18-fluorodeoxyglucose positron emission tomography scanning. Total and regional LV scar size were calculated. Response to CRT was pre-specified as > or =10% improvement in LV end-systolic volume and/or > or =5% absolute ejection fraction improvement. RESULTS: Responders (n = 31) had significantly less lateral wall scar than responders (5.6% compared with 24.5%, P = .008) but a similar extent of global and septal scar. In the ischemic group, responders' median lateral wall scar size was 11.2% (IQR 0.0 to 31.2), compared with 47.8% (IQR 21.2 to 73.4) P = .052. In the ischemic group, for each 5% absolute decrease in lateral scar size, the odds ratio of being a responder was 1.87 (95% CI: 1.11 to 3.15, P = .018). In the nonischemic group, median lateral wall scar size of responders was 3.4% (IQR 0.0 to 10.3) compared with the nonresponders, 14.4% (IQR 9.0 to 27.8), P = .046. CONCLUSION: Responders had significantly less lateral wall scar than nonresponders, but a similar extent of global and septal scar. This held true in both ischemic and nonischemic cardiomyopathy patients.