Background: Intravascular ultrasound (IVUS) offers a new modality by which to image the vessel wall in high resolution. The aim of the study was to classify atherosclerotic lesions using IVUS according to American Heart Association (AHA) recommendation.
Methods: IVUS was performed using a 20 or 30 MHz mechanically rotated catheter in 190 patients (aged from 35 to 75 years, mean 59 +/- 9 years) who presented with suspicion of coronary artery disease based on clinical examination.
Results: Of the 190 patients, 49 (26%) (group A) were found to have normal or nearly normal coronary arteries, whereas the other 141 (74%) (group B) had significant angiographic stenosis (> 50% luminal narrowing). IVUS image interpretation was based on the recommendation of the Committee on Vascular Lesions of the Council on Atherosclerosis (AHA). In group A, a total of 822 segments were evaluated with IVUS; 444 (54%) were found to have plaque formation. Among these 444 segments, type II lesions were found in 145 (33%), type III lesions in 110 segments (25%), type IV and Va lesions in 169 segments (38%), and type Vb in 18 segments (4%). The severity of plaque area stenosis increased from type II to IV. In group B, only the most stenotic segments (n = 141) on angiography were selected for analysis. No significant differences were found among different lesion types with respect to the severity of plaque area stenosis. Type Vb and Vc lesions presented mainly, but not exclusively, as stable angina, whereas type VI lesions presented mainly as unstable angina. Some patients (12%) with stable angina had complicated lesions (type VIa-VIc).
Conclusions: It is now possible to use intravascular ultrasound to classify atherosclerotic lesions according to the AHA recommendations that were based on histological examination. Standardized reports of IVUS can now be based on these recommendations. Even in angiographically normal coronary arteries, advanced atherosclerotic lesions are found, explaining the potential risk of acute coronary syndromes in this group of patients. In patients with angiographically severe coronary disease, clinical symptoms correlate mainly with plaque characteristics, rather than with the severity of stenosis.