Abstract Background/Introduction Non-invasive, quantitative and objective phenotyping of the longitudinal distribution of coronary artery disease (CAD) is feasible using the CCTA-based Simulated Pressure Loss Index (CT-SPLI) a novel metric derived from CT-based fractional flow reserve (CT-FFR) estimates. By combining the magnitude and extend of longitudinal epicardial pressure losses, CT-SPLI provides a continuous metric from 0 to 1; values close to 0 represent diffuse CAD, whereas values close to 1 represent focal CAD. Purpose The aim of this study is to describe the associations of non-invasively assessed CAD phenotypes with myocardial ischemia and pathological myocardial blood flow derived from positron emission tomography/computed tomography-myocardial perfusion imaging (PET/CT-MPI). Methods A total of 169 patients who underwent hybrid CCTA and 13N-NH3 PET/CT-MPI for evaluation of suspected chronic coronary syndrome were retrospectively included. CT-FFR analysis and CT-SPLI calculation were performed in 362 coronary arteries with plaques and luminal diameter stenosis ≥ 20% to 90%. Patterns of CAD at the arterial level were categorised into diffuse, mixed, and focal based on the tertiles of the CT-SPLI distribution. Using fusion with CCTA, each artery was assigned to its corresponding myocardial territory and the presence of concordant myocardial ischemia on PET/CT-MPI was assessed by two independent readers. Regionally impaired regional myocardial blood flow was defined as stress myocardial blood flow (sMBF) ≤1.86 ml/min/g or myocardial flow reserve (MFR) ≤2.0. Results Mean CT-SPLI was 0.50 ±0.15 and coronaries were phenotyped as diffuse CAD (CT-SPLI ≤0.43), mixed CAD (0.43 CT-SPLI ≤ ct-spli ≤0.58)0.58). In total, 36 arteries (10%) subtended ischemic myocardium, 153 (42.3%) subtended myocardium with reduced sMBF and 81 (22.4%) subtended myocardium with reduced MFR. Higher rates of myocardial ischemia were observed in arteries with diffuse disease, affecting 17.2% compared to mixed and diffuse CAD (11.7% and 0.8% respectively). Logistic regression identified CT-SPLI as an independent predictor of ischemia (OR 0.01, 95% CI 0.00–0.04; p0.001), and with an area under the ROC curve of 0.79 (95% CI: 0.58 - 0.90; p=0.001), outperforming traditional variables including CT-FFR, stenosis severity, and coronary calcium score. Similarly, diffuse disease was significantly associated with impaired myocardial blood flow: 51.6% had diminished stress MBF (vs. 36.7% mixed and 38.3% focal; p=0.035), while 48.1% had impaired MFR (vs. 25.9% for both mixed and focal; p=0.008). ≤0.58). p=0.001) Conclusion CT-SPLI-based diffuse pattern of CAD is associated with myocardial ischemia and impaired myocardial blood flow more frequently compared to mixed and focal CAD phenotypes. CT-SPLI can provide valuable non-invasive insights into the physiological relevance of CAD.
Moysidis et al. (Thu,) studied this question.