Scar burden by myocardial perfusion imaging predicts echocardiographic response to cardiac resynchronization therapy in ischemic cardiomyopathy

Background About 30% of patients with heart failure do not respond to cardiac resynchronization therapy (CRT). We hypothesized that scar burden can predict poor response to CRT in patients with ischemic cardiomyopathy (ICM). Methods Fifty patients (age, 68.5 +/- 9.2 years; 84% men; mean left ventricular ejection fraction (LVEF), 19.7% +/- 5.2%) with ICM who underwent CRT-defibrillator implantation and (TI)-T-201 single photon emission computed tomography myocardial perfusion imaging were included. Myocardial perfusion imaging studies were read quantitatively, generating a summed perfusion score (SPS). Left ventricular (LV) lead position was determined by chest radiography. Echocardiograms were performed before and after (median, 11.0 months) CRT. Results Echocardiographic response, defined as >= 15% relative increase in LVEF, was documented in 28 (56%) patients. The mean SPS (18.8 +/- 11.3 vs 33.7 +/- 11.1; P = .000025) and the average scar density in the segments immediately adjacent to the LV lead (0.70 +/- 0.91 vs 1.64 +/- 0.82; P =.0004) were significantly lower in responders versus nonresponders. Global scar burden (r = -0.53; P = .00007), scar burden near the LV lead (r = -0.49; P = .0003), and the number of segments with a score of 4 (r = -0.53; P = .0007) inversely correlated with increase in LVEF after CRT. The hazard ratio for nonresponse increased with increasing tertiles of global SPS, scar density in the vicinity of the LV lead, and number of segments with transmural scar (ie, perfusion score = 4). Conclusions Higher overall scar burden, a larger number of severely scarred segments, and greater scar density near the LV lead tip portend an unfavorable response to CRT in ICM patients. Prospective confirmation of these findings is warranted.