Abstract 906: Healing of Thin-Capped Fibroatheroma Assessed by Serial VH-IVUS Tissue Characterization

Abstract

Thin-cap fibroatheromas (TCFA) are prone to plaque rupture and thrombosis. Intravascular ultrasound (IVUS) virtual histology (VH) assesses plaque composition and lesion morphology in vivo. Methods & Results: We used serial (baseline and follow-up @11 mos) VH-IVUS to study non-culprit plaque morphology in 221 lesions (plaque burden >40%) in 106 pts. Lesions were classified into 4 types based on plaque composition; pathological intimal thickening (PIT), thin-capped fibroatheroma (TCFA), thick-capped fibroatheroma (ThCFA), fibrotic/fibrocalcific. At baseline, 21 lesions were TCFAs (confluent necrotic core contacting to the lumen). Overall during follow-up (Figure ), 16/21 (76%) TCFAs healed: 13 became ThCFAs, 2 TCFAs became PIT, 1 TCFA became fibrotic, and 5 TCFAs (24%) remains unchanged although the location of the necrotic core in contact with the lumen shifted axially. Compared to TCFAs that healed, TCFAs that remained TCFAs were more often proximal in location (distance from coronary ostium to the lesion of 19±6 vs. 41±22mm, respectively, p=0.037) and had larger lumen area (9.9±3.1 vs. 6.9±1.8 mm2, p=0.013), vessel area (22.8±6.4 vs. 15.3±2.6 mm2, p=0.001), plaque area (12.9±4.9 vs. 8.4±1.7 mm2, p=0.005), calcium area (1.3±0.6 vs. 0.6±0.3 mm2, p=0.014), and necrotic core area (2.6±1.0 vs. 1.6±0.7 mm2, p=0.015). In addition, 6 new TCFAs developed; these 6 late-developing TCFAs had the appearance of PIT at baseline (Figure ). Conclusion: Although most TCFAs seem to stabilize or heal during 12 mos follow-up, proximal TCFAs in larger vessels with more plaque and calcium and a larger necrotic core appear to heal less often and new TCFAs can develop.