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Abstract Background CT-Simulated Pressure Loss Index (CT-SPLI) is a novel coronary-artery-specific index, based on computational hemodynamics. Quantifying the spatial distribution of hyperemic epicardial flow resistances, it enables phenotyping of coronary artery disease (CAD) as diffuse or focal. We investigated the interplay between CAD phenotypes with myocardial perfusion and myocardial blood flow and the diagnostic performance of CT-SPLI using PET-myocardial perfusion imaging (MPI) as reference. Methods Retrospectively, 54 patients with suspected CAD referred for hybrid CCTA and 13N-NH3-PET-MPI between 2015-2021 were included. CT-SPLI was calculated (XFFR, GE Healthc.) in all coronaries with plaques and lumen diameter narrowing of 25-90%. Based on the presence of plaques with ≥50% stenosis, arteries were classified as stenotic or non-stenotic. Using fusion with CCTA, each artery was assigned to the respective myocardial territory. Abnormal PET-MPI was defined as a. presence of regional myocardial ischemia, or b. regionally reduced stress myocardial blood flow (sMBF ≤1.86ml/min/gr) or c. regionally reduced myocardial blood flow reserve (MFR ≤2) or d. a composite of regionally abnormal myocardial-perfusion and/or impaired-blood flow. Results 54 patients (mean age 61±9.9 years; 72% male) were included. 105 arteries were analyzed and 30 (29%) of them subtended ischemic myocardium, 30 (29%) subtended myocardium with reduced sMBF and 25 (24%) subtended myocardium with reduced MFR. Median CT-SPLI was 0.48 0.26,0.60 and coronaries were phenotyped as diffuse (CT-SPLI≤0.48) or focal (CT-SPLI0.48). No difference was observed in the frequency of stenotic lesions between arteries with diffuse vs focal CAD phenotype (60% vs 45% p=0.57). Coronaries subtending ischemic myocardium, myocardium with reduced sMBF and reduced MFR, had lower CT-SPLI values compared to those subtending normal myocardium (0.36 vs 0.52, 0.41 vs 0.49 and 0.39 vs 0.50, respectively; all p0.01). Arteries with diffuse CAD were more associated with ischemia (x2 =11, p=0.0009), reduced sMBF (x2 =6.1, p=0.014) and reduced MFR (x2 =7.8, p=0.005) compared to arteries with focal CAD. Similarly, coronaries subtending myocardium with pathological perfusion and/or blood flow had lower CT-SPLI values compared to normal myocardium (0.38 vs 0.55, p0.0001). Diffusely diseased arteries were predominantly associated with regionally pathological myocardial-perfusion and/or blood flow (x2 =19.1, p0.0001). The AUC ROC of CT-SPLI to detect regionally ischemic myocardium and/or impaired blood flow was 0.793 with 84.6% sensitivity and 67.9% specificity. Conclusions Coronaries with diffuse CAD phenotype are more often associated with myocardial ischemia and pathological myocardial blood flow compared to those with focal CAD phenotype. Non-invasive assessment of CT-SPLI can provide novel insights in the interactions between coronary atherosclerosis, myocardial perfusion and myocardial blood flow.Figure 1
Steffek et al. (Thu,) studied this question.