Abstract 19211: The Relationship Between Anatomical and Functional Coronary Artery Disease Severity and Transmural Myocardial Blood Flow Distribution

Abstract

Objectives: To determine the impact of lesion severity as assessed by the fractional flow reserve (FFR) on the transmural perfusion gradient (TPG) using H215O positron emission tomography (PET) imaging in patients evaluated for coronary artery disease (CAD). Background: Myocardial ischemia occurs principally in the subendocardial layer, whereas conventional myocardial perfusion imaging provides no information on the transmural myocardial blood flow (MBF) distribution. Methods: Sixty-six patients evaluated for CAD were prospectively enrolled and underwent H215O PET imaging for quantification of TPG. Subsequently, invasive coronary angiography was performed and FFR obtained in all coronary arteries irrespective of the PET imaging results. Results: Thirty (45%) patients were diagnosed with significant CAD (i.e. FFR ≤ 0.80), whereas on a per vessel analysis (n=198), 53 (27%) displayed a positive FFR. Hyperemic MBF decreased significantly from 3.09 ± 1.16 to 1.67 ± 0.57 mL·min-1·g-1 (p < 0.001) in nonischemic and ischemic myocardium, respectively. The TPG decreased during hyperemia as compared with baseline (1.20 ± 0.14 vs. 0.94 ± 0.17, p<0.001), and was lower in arteries with a positive FFR (0.97 ± 0.16 vs. 0.88 ± 0.18, p<0.01). A TPG threshold of 0.94 yielded anc accuracy to detect CAD of 59%, which was inferior to transmural MBF with an optimal cutoff of 2.20 mL·min-1·g-1 and an accuracy of 85% (p < 0.001). Conclusions: Cardiac H215O PET imaging is able to detect TPGs and demonstrates a significantly lower hyperemic TPG in ischemic myocardium. However, the diagnostic accuracy of TPG seems to be limited compared to quantitative transmural MBF.