Impact of nitroglycerin on machine-learning fractional flow reserve in coronary computed tomography (CT)-angiography

Background: Nitroglycerin administration prior to examination improves stenosis assessment of coronary computed tomography (CT) angiography (CCTA). However, whether nitroglycerin influences CT-derived fractional flow reserve (FFR, CT-FFR) evaluation remains unclear. This study aimed to investigate the effect of nitroglycerin on diagnostic performance of CT-FFR. Methods: In this single-center retrospective study, 107 consecutive patients suspected of coronary artery disease (CAD) with nitroglycerin administration prior to CCTA in 2019 were matched to 107 patients without nitroglycerin in 2016 from Fuwai Hospital. All patients underwent CCTA and invasive FFR in a month. Vessel-based and patient-based accuracy and diagnostic performance of CT-FFR were compared between the two groups, as well as image quality, coronary artery diameter and evaluability. Quantitative variables were compared by Kruskal-Wallis H test. Categorical variables and rates were compared by chi 2 2 test or Fisher exact test. Results: A total of 214 patients (56.1 +/- 8.9 years, 155 male) with 237 target lesion vessels were analyzed, including 120 vessels in nitroglycerin and 117 vessels in non-nitroglycerin group. Per-vessel based accuracy of CT-FFR was higher in nitroglycerin group {80.0% [95% confidence interval (CI): 71.7-86.7%] vs. 68.4% (59.1-76.7%), P=0.041}. On a per-patient basis, nitroglycerin administration improved the accuracy [83.2% (74.7-89.7%) vs. 68.2% (58.5-76.9%), P=0.01], specificity [82.7% (69.7-91.8%) vs. 61.9% (48.8-73.9%), P=0.01], positive predictive value (PPV) [83.6% (73.6-90.4%) vs. 58.6% (50.0-66.9%), P=0.004], and area under the curve (AUC) [0.83 (0.75-0.89) vs. 0.71 (0.61-0.79), P=0.03] of CT-FFR. Vessel diameters (left main arteries: 4.3 vs. 3.8 mm, P<0.001; left anterior descending arteries: 3.1 vs. 2.9 mm, P=0.001; left circumflex arteries: 2.9 vs. 2.7 mm, P=0.01; right coronary arteries: 3.7 vs. 3.4 mm, P=0.001) and number of evaluable coronary arteries (11.0 vs. 8.0, P<0.001) were larger in nitroglycerin group. Conclusions: Nitroglycerin administration prior to CCTA has positive effects on diagnostic performance of CT-FFR.