Subendocardial Systolic Hypoperfusion in Stenotic Coronary Territories: Demonstration by 256-Slice Coronary CT Angiography

Purpose: We propose a new, Myocardial Perfusion Imaging (MPI) with coronary CTA, and investigate the diagnostic ability of subendocardial hypoperfusion for Coronary Artery Disease (CAD) based on degree of coronary stenosis. Methods: In twenty CAD patients, Coronary CTA and Invasive Coronary Angiography (CAG) were performed. CT-Myocardial Perfusion Image (MPI) was reconstructed at 4 cardiac phases (0%, 40%, 60%, and 80% of the R-R interval), applying CT number measured in Hounsfield Unit (HU) as an estimate of perfusion. A myocardial segment with subendocardial low attenuation at endsystole was defined as subendocardial-systolic-hypoperfusion (SSH). Results: Using >50% stenosis on CAG as standard, SSH diagnosed stenotic coronary territories with 63% sensitivity, 82% specificity, and 70% accuracy. Using >75% stenosis on CAG as standard, SSH diagnosed stenotic coronary territories with 73% sensitivity, 80% specificity, and 77% accuracy. The use of the SSH sign led to accurate diagnosis (result of CAG) in 9 of 60 territories (15%), which could not be assessed due to severe coronary calcification. Conclusion: SSH is frequently seen in the stenotic coronary territories. SSH might provide powerful information when the assessment of coronary artery is made difficult by severe calcification.