Myocardial scarring in the left ventricular basal posterolateral region may negatively impact on response to cardiac resynchronization therapy: analysis with quantitative myocardial perfusion SPECT

Purpose: About 30% of patients with heart failure do not respond to Cardiac Resynchronization Therapy (CRT); ischemic cardiomyopathy negatively influences the response. The study objective was to determine the impact of global and regional myocardial scar burden on CRT outcomes by using AutoQUANT. Methods: We studied 38 consecutive CRT recipients (28 men; age 70±7 years old; ischemic cardiomyopathy, n= 12; Left Ventricular [LV] ejection fraction 23.5±9.4%; QRS duration 158±30ms). All the patients underwent resting 99mTc-MIBI gated-myocardial perfusion SPECT prior to CRT. The SPECT images were analyzed by AutoQUANT 7.2 to quantify the global Defect Extent (DE), an index of global scarring, as well as the regional DE in each of the 17 segments of the LV, an index of regional scar burden. CRT response was defined as a decrease of >10% in the LV end systolic volume at 6 months after CRT device implantation based on the QGS analysis of the SPECT images. Results: Twelve patients did not respond CRT. The response rate was lower in patients with ischemic cardiomyopathy than those with non-ischemic cardiomyopathy (25% vs. 85%, p<0.001). The non-responders had a higher global DE than responders (35±17% vs. 22±10%, p=0.004). The non-responders also showed higher regional DEs in the lateral adjoining areas as compared with the responders: the basal posterolateral region (45±30% vs. 14±23%, p=0.001), the mid posterolateral region (42±41% vs. 15±27%, p=0.02), and apical lateral region (41±39% vs. 16±21%, p=0.01). Logistic regression analysis disclosed the following significant predictors of negative response to CRT: global DE (crude odds ratio [OR] 1.08, 95% confidence interval [CI] 1.02-1.07, p=0.01), the basal posterolateral DE (crude OR 1.04, 95% CI 1.01-1.07, p=0.005), the mid posterolateral DE (crude OR 1.02, 95% CI 1.00-1.04, p=0.03), and apical lateral DE (crude OR 1.03, 95% CI 1.00-1.06, p=0.02). After adjusting the type of cardiomyopathies, only the basal posterolateral DE remained as a significant predictor (adjusted OR 1.04, 95% CI 1.00-1.07, p=0.03). Receiver operating characteristic curve analysis of this segment showed that the AUC was 0.828. Using a cutoff point of 23.5% provided a sensitivity of 84.0% and specificity of 76.9% for the prediction of negative response to CRT. Conclusions: Myocardial scarring assessed by myocardial quantitative perfusion SPECT may negatively impact response to CRT. The regional scar burden at the basal posterolateral wall is most likely to predict unfavorable response to CRT irrespectively of the type of cardiomyopathies.