Impact of sublingual nitroglycerin dosage on FFR CT assessment and coronary luminal volume–to–myocardial mass ratio

Objectives Fractional flow reserve computed tomography (FFR CT ) depends upon nitroglycerin (NTG) inducing maximal hyperemia. However, the impact of NTG dosages on FFR CT analysis including coronary volume–to–mass ratio (V/M) is unknown. Methods Eighty patients with repeat coronary CT angiograms (CCTAs) with different sublingual spray NTG doses (0.4 mg and 0.8 mg) were retrospectively analyzed with 45 patients excluded. Patient and scan demographics, post-stenosis and nadir FFR CT values, coronary volume, and coronary volume–to–mass ratio (V/M) were compared at initial CCTA (0.4 mg NTG) and follow-up CCTA (0.8 mg NTG). Differences were compared by Wilcoxon signed-rank test. Results Thirty-five patients were included (time between CCTAs, 3.9 ± 1.6 years). Segment involvement score was 2.4 ± 3.3 and 2.8 ± 3.4 at initial and repeat CCTA (0.4 and 0.8 mg NTG), respectively ( p = 0.004). There was similar image quality (4.1 ± 0.7 vs 4.1 ± 0.8; p = 0.51). Nadir FFR CT values did not differ in the left (0.4 mg, 0.80 ± 0.08 vs 0.8 mg, 0.80 ± 0.03; p = 0.66), right (0.4 mg, 0.90 ± 0.04 vs 0.8 mg, 0.90 ± 0.06; p = 0.25), or circumflex coronaries (0.4 mg, 0.87 ± 0.06 vs 0.8 mg, 0.88 ± 0.06; p = 0.34). Post-stenosis FFR CT values did not differ ( p = 0.65). Coronary volume increased with 0.8 mg of NTG (2639 ± 753 mm 3 vs 2844.8 ± 827 mm 3 ; p = 0.009) but V/M ratio did not ( p = 0.20). Conclusions Use of 0.8 mg versus 0.4 mg of NTG in routine clinical CCTAs significantly increased coronary volume determined from FFR CT analysis but did not alter FFR CT or V/M. Further evaluation of repeat CCTAs in a more contemporaneous fashion using varied nitrate doses and disease severity is needed. Key Points • Fractional flow reserve from computed tomography ( FFR CT ) is a noninvasive method for evaluating the coronary arteries and relies on nitroglycerin ( NTG ) to induce coronary vasodilation , but the impact of different NTG dosages is unknown . • Retrospective analysis evaluated use of different NTG doses on FFR CT . • Increased NTG dose increased coronary luminal volume on FFR CT analysis , but did not change FFR CT values .