Quantitative Measures of Coronary Stenosis Severity by 64-Slice CT Angiography and Relation to Physiologic Significance of Perfusion in Nonobese Patients: Comparison with Stress Myocardial Perfusion Imaging

¹ Department of Cardiology, Yokosuka Kyosai Hospital, Yokosuka, Japan
² Department of Nephrology and Cardiology, International Medical Center of Japan, Tokyo, Japan
³ Department of Cardiology, University of Tsukuba Graduate School of Comprehensive Human Science, Tsukuba, Japan
⁴ Department of Cardiovascular Medicine, Tokyo Medical and Dental Postgraduate School of Medicine, Tokyo, Japan

^* To whom correspondence should be addressed. E-mail: asato{at}yf6.so-net.ne.jp.

	Abstract

Coronary stenosis severity by 64-slice CT angiography (CTA) is acceptably correlated with intravascular ultrasound. Stress myocardial perfusion imaging using SPECT is an established method for assessment of the functional significance of coronary stenosis. Our aim was to assess a clinical validation of quantitative measurements of coronary stenosis severity by 64-slice CTA and the relation to the physiologic significance of myocardial perfusion. Methods: One hundred four patients with suspected coronary artery disease underwent 64-slice CTA and stress ²⁰¹Tl SPECT. The stenosis severities of 105 coronary lesions assessed by CTA with sufficient image quality were compared with the results of stress ²⁰¹Tl SPECT. The body mass index (BMI) of the patients was 23.8 kg/m² (range, 21.1–25.6 kg/m²). Results: Reversible defects began to increase progressively when the area of stenosis was at least 60%, and the prevalence of these reversible defects and their severity significantly increased as the degree of stenosis increased. When stenosis severity by CTA is < 60%, ischemia is seldom observed; when stenosis severity is 80%, ischemia is common (86%). For intermediate stenosis severity values of 60%–70%, the prevalence of reversible defects was 9 of 27 vessels (33%), and for stenosis severity values of 70%–80%, the prevalence was 20 of 37 vessels (54%). When evaluating the diagnostic accuracy of stenosis severity by CTA to identify patients with ischemia excluding all nonevaluable vessels, applying stenosis thresholds of >70% results in 79% sensitivity, 92% specificity, 66% positive predictive value, and 96% negative predictive value. A lesion minimal luminal cross-sectional area of < 3.7 mm² was a good accurate cutoff value for significant coronary narrowing using stress SPECT, with a sensitivity of 88% and specificity of 83% by receiver-operating-characteristic analysis. Conclusion: Despite an excellent negative predictive value to rule out the presence of ischemia, 64-slice CTA alone is a poor discriminator of the functional significance of myocardial ischemia in a highly selected patient population with a low BMI.

Key Words: CT angiography, imaging, ultrasound, coronary stenosis, perfusion

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