This in vivo correlation between ICUS and EBCT demonstrates that EBCT is a noninvasive method that helps to visualize the atherosclerotic process by localization and quantification of coronary artery calcifications. EBCT detects calcified plaques with high accuracy. Plaques without ultrasound signs of calcifications can be detected by EBCT but with lower sensitivity but equivalent specificity.

Background-Myocardial fractional flow reserve (FFR) is based on pressure measurements. We have now sought to establish a Doppler-based concept of relative flow velocity reserve (RFVR) for the functional assessment of stenosis severity in epicardial coronary arteries. A clear threshold value to discriminate the functional severity of a coronary stenosis does not exist for coronary flow velocity reserve (CVR) based on intracoronary Doppler measurements. In contrast, the concept of FFR, which is based on intracoronary pressure measurements, has been extensively validated. An FFR value below 0.75 reliably indicates a significant stenosis. Methods and Results-RFVR is calculated as the ratio between distal CVR in the stenosed target vessel and distal CVR in a nonstenotic reference vessel. In 21 patients, RFVR was determined in 24 target vessels by use of intracoronary adenosine and correlated to the FFR, determined as the ratio of mean poststenotic to aortic pressures, in the target vessel. Stenosis severity was classified according to quantitative coronary angiography analysis. Reference diameter was 3.0Ϯ0.4 mm (meanϮSD), and area stenosis was 74Ϯ15% (range, 40% to 95%). CVRs in the target and reference vessels were 2.1Ϯ0.5 and 2.6Ϯ0.

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