In vivo quantitative tissue characterization of angiographically normal coronary lesions and the relation with risk factors: a study using integrated backscatter intravascular ultrasound.

BACKGROUND Autopsy studies have shown atherosclerotic changes in angiographically normal coronary lesions (ANCL), and conventional intravascular ultrasound shows intimal thickening in these lesions, but cannot differentiate the lipid core. Accurate characterization of ANCL is essential to prevent progression to coronary artery disease. METHODS AND RESULTS ANCL (n=120) were analyzed by integrated backscatter intravascular ultrasound (IB-IVUS) in 30 patients with stable angina pectoris. Of the 120 arterial segments analyzed by IB-IVUS, 78 (65%) showed lipid cores of 0.69+/-0.35 mm2 with fibrous caps of 200+/-100 microm thick, 44 (37%) had intimal hyperplasia with a thickness of 350+/-100 microm, and 65 (54%) showed fibrosis in the intimal wall without lipid core with a thickness of 450+/-150 microm. The diabetes mellitus (DM) group (n=14) had significantly (p<0.05) bigger lipid cores (0.62+/-0.38 mm2) and thinner intimal hyperplasia (100+/-100 microm) compared with the non-DM group (0.31+/-0.33 mm2, 150+/-150 microm, respectively). The hypertension (HT) group (n=23) had significantly more intimal hyperplasia (150+/-150 microm) compared with the non-HT group (50+/-100 microm). Hyperlipidemia (n=16) or smoking (n=6) did not significantly affect tissue characteristics. CONCLUSION IB-IVUS showed various types of plaque in ANCL and the plaque characteristics were affected by DM and HT. The results provide new clinical insight into the early stage of human coronary atherosclerosis.