Quantitative [13N]ammonia/[18F]FDG PET/CT predicts left ventricular functional recovery after CABG in ischemic cardiomyopathy: An exploratory study

BACKGROUND: In patients with ischemic cardiomyopathy (ICM), accurate preoperative identification of viable myocardium is clinically important to identify those who are likely to benefit from coronary artery bypass grafting (CABG). Although the PET perfusion-metabolism mismatch index has long been used to assess myocardial viability, its value in predicting contractile recovery remains controversial. Quantitative metabolic indices based on standardized uptake value (SUV) may provide complementary prognostic information. METHODS: This single-center retrospective cohort study included 53 patients with ICM who underwent preoperative [13N]ammonia/[18F]FDG PET/CT followed by isolated CABG. Conventional perfusion-metabolism indices were compared with SUV-based indices. The evaluated outcomes were postoperative increases in left ventricular ejection fraction (ΔLVEF) of ≥5% and ≥10% on follow-up echocardiography, and time to first major adverse cardiovascular event (MACE). Each PET parameter was evaluated in a separate multivariable Firth-penalized logistic regression model adjusted a priori for age, baseline LVEF, history of coronary artery disease, and diabetes. The predictive performance was assessed by receiver operating characteristic analysis, and time to MACE by Cox regression with the adjustment of multiple testing and model optimism. RESULTS: Of the 53 patients, 32 (60.4%) achieved ΔLVEF ≥5% and 25 (47.2%) achieved ΔLVEF ≥10%. The infarct-to-non-infarct SUV ratio (SUVR) was associated with ΔLVEF ≥5% (odds ratio [OR] 1.94 per 0.1-unit increase, 95% confidence interval [CI] 1.28-3.25; P < 0.001; q = 0.003) and ΔLVEF ≥10% (OR 1.53, 95% CI 1.11-2.29; P = 0.004; q = 0.035). For the prediction of ΔLVEF ≥5%, SUVR had a higher area under the curve (AUC) than the mismatch index (0.83 vs 0.62; DeLong P = 0.0049; q = 0.0147). For the prediction of ΔLVEF ≥10%, the AUCs did not differ (0.73 and 0.63; DeLong P = 0.200; q = 0.383). No individual PET parameter was associated with time to first MACE in adjusted Cox models. CONCLUSIONS: SUVR showed greater discrimination for postoperative ΔLVEF ≥5% than the conventional perfusion-metabolism mismatch index. This finding supports SUVR as a quantitative adjunct to conventional PET viability assessment and warrants further multicenter validation.