Abstract： Objective Myocardial functional outcome after revascularization of coronary chronic total occlusion (CTO) was prospectively predicted using extracellular volume fraction (ECV) based on cardiovascular magnetic resonance (CMR). Methods Thirty patients with CTO underwent CMR before and 6 months after percutaneous coronary intervention (PCI) were enrolled. The CMR scan protocol included cine, pre?contrast and post?contrast T1 mapping and late gadolinium enhancement (LGE). Ejection fraction (EF) and segmental wall thickening (SWT) were calculated using CVI 42 software. SWT less than 45% indicated myocardial segment dysfunction. According to the American Heart Association (AHA) scientific statement, the dysfunctional segments assigned to CTO vessel were selected, and three baseline imaging markers, ECV, transmural extent of infarction (TEI) and unenhanced rim thickness (RIM) were respectively evaluated. The myocardial segments were divided into two subgroups, group with well?developed collaterals and group with poorly?developed collaterals, based on the collateral circulation using Rentrop classification. Baseline and follow?up values of SWT and EF were evaluated using paired Student′s t?test. Using an increase in SWT>10% as standard reference, ROC analysis was conducted to describe the predictive performance of baseline markers. A mixed linear model was used to probe the relationship between collateral circulation and SWT. Stepwise logistic regression analysis was used to determine the independent predictors of regional functional recovery. The differences of EF between poorly?developed and well?developed collaterals were compared by Student t test. Results The baseline mean segmental wall thickening (SWT) of the dysfunctional segments increased from 21.6% (9.7%, 33.3%) to 38.4% (19.0%, 51.2%) after PCI (Z=-6.869, P<0.001), and EF was also significantly higher compared with baseline (54.5%±8.5 % vs. 50.7%± 6.6%, t=-5.706, P<0.001). ECV showed good performance in predicting functional recovery with cutoff value 34.7%, area under ROC curve (AUC) 0.86, sensitivity 91%, and specificity 66%. The AUC of ECV was superior to TEI and RIM (AUC: 0.75 and 0.73, all P value<0.01). The segments with well?developed collaterals were associated with a higher SWT at follow?up [46.6% (36.6%, 64.2%) vs. 33.5% (12.8%, 47.8%),F=5.791, P=0.02]. Logistic regression analysis demonstrated that mean segmental ECV was the only independent predictors of regional functional outcome after PCI (OR=0.83, 95% confidence interval: 0.77—0.89; P<0.001). Conclusions ECV by CMR may provide incremental value for the prediction of regional functional recovery in CTO patients, and baseline collateral circulation correlates with the regional systolic function after revascularization.