The Dynamic Nature of Coronary Artery Lesion Morphology Assessed by Serial Virtual Histology Intravascular Ultrasound Tissue Characterization

We used virtual histology intravascular ultrasound (VH-IVUS) to investigate the natural history of coronary artery lesion morphology. Plaque stability is related to its histological composition. We performed serial (baseline and 12-month follow-up) VH-IVUS studies and examined 216 nonculprit lesions (plaque burden ≥40%) in 99 patients. Lesions were classified into pathological intimal thickening (PIT), VH-IVUS–derived thin-capped fibroatheroma (VH-TCFA), thick-capped fibroatheroma (ThCFA), fibrotic plaque, and fibrocalcific plaque. At baseline, 20 lesions were VH-TCFAs; during follow-up, 15 (75%) VH-TCFAs “healed,” 13 became ThCFAs, 2 became fibrotic plaque, and 5 (25%) VH-TCFAs remained unchanged. Compared with VH-TCFAs that healed, VH-TCFAs that remained VH-TCFAs located more proximally (values are median [interquartile range]) (16 mm [15 to 18 mm] vs. 31 mm [22 to 47 mm], p = 0.013) and had larger lumen (9.1 mm2[8.2 to 10.7 mm2] vs. 6.9 mm2[6.0 to 8.2 mm2], p = 0.021), vessel (18.7 mm2[17.3 to 28.6 mm2] vs. 15.5 mm2[13.3 to 16.6 mm2]; p = 0.010), and plaque (9.7 mm2[9.6 to 15.7 mm2] vs. 8.4 mm2[7 to 9.7 mm2], p = 0.027) areas; however, baseline VH-IVUS plaque composition did not differ between VH-TCFAs that healed and VH-TCFAs that remained VH-TCFAs. Conversely, 12 new VH-TCFAs developed; 6 late-developing VH-TCFAs were PITs, and 6 were ThCFAs at baseline. In addition, plaque area at minimum lumen sites increased significantly in PITs (7.8 mm2[6.2 to 10.0 mm2] to 9.0 mm2[6.5 to 12.0 mm2], p < 0.001), VH-TCFAs (8.6 mm2[7.3 to 9.9 mm2] to 9.5 mm2[7.8 to 10.8 mm2], p = 0.024), and ThCFAs (8.6 mm2[6.8 to 10.2 mm2] to 8.8 mm2[7.1 to 11.4 mm2], p < 0.001) with a corresponding decrease lumen areas, but not in fibrous or fibrocalcific plaque. Most VH-TCFAs healed during 12-month follow-up, whereas new VH-TCFAs also developed. PITs, VH-TCFAs, and ThCFAs showed significant plaque progression compared with fibrous and fibrocalcific plaque.