Distensibility of the ascending aorta, measured non-invasively, was compared with values obtained by invasive techniques in 46 males (30 patients with coronary artery disease and 16 age-matched normal subjects). Aortic diameters were measured at a level 3 cm above the aortic valve using both echocardiographic and angiographic techniques. Aortic distensibility was calculated from the aortic diameters and aortic pressure or brachial artery pressure using the formula: 2 x (change in aortic diameter)/(diastolic aortic diameter) x (change in aortic pressure). Distensibility of the ascending aorta determined non-invasively was closely related to that obtained by direct measurements (r = 0.949, P less than 0.001). Patients with coronary artery disease had similar pressures, but markedly lower distensibility than normal subjects, as shown by both invasive and non-invasive techniques. The results indicate that aortic distensibility in patients with coronary artery disease can be obtained non-invasively with a high degree of accuracy.

, when the echolucent area to plaque ratio is greater than 38.5 (17.1)%, and when the fibrous cap is thinner than 0.7 mm. IVUS can identify plaque rupture and vulnerable plaques. This may influence patient management and treatment. (Heart 1999;81:621-627) Keywords: intravascular ultrasound; atherosclerosis; unstable angina; myocardial infarction; plaque rupture Plaque rupture and the subsequent thrombus formation are major events which lead to complex lesions and contribute to the pathogenesis of acute coronary syndromes such as unstable angina, myocardial infarction, and sudden death.1-5 After plaque rupture, the atheroma can be washed out and an open cavity remains.1 5 6 Coronary angiography, which provides a silhouette of the vessel lumen, can only indirectly suggest plaque rupture in the form of a filling defect caused by intraluminal thrombus or a contrast filled crater from deep ulceration. Intravascular ultrasound (IVUS) oVers a new method of for visualising the coronary artery wall, plaque morphology, and plaque composition, 9-14 and as such has the potential to identify plaque disruption, as reported in a preliminary study. 15The purposes of the present study were first, to visualise the characteristics of ruptured plaques and second, to correlate the plaque characteristics with clinical symptoms and to establish a quantitative index of plaque vulnerability with IVUS. Methods PATIENTSIn our cardiovascular catheterisation laboratory, we used IVUS after coronary angiography to examine 144 consecutive patients (aged from 35 to 75 years) who present with angina associated with ischaemic ECG changes on exercise. To evaluate unstable patients (within two weeks), we used the clinical classification proposed by Braunwald. 16 All patients provided written informed consent for IVUS examination. Patients with acute myocardial infarction and in an unstable situation, such as cardiogenic shock, who were not suitable for IVUS, were not included.

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