[Plaque features in saphenous vein graft evaluated by virtual histology intravascular ultrasound]

Objective: To investigate the features of plaques of saphenous venous graft (SVG) with virtual histology intravascular ultrasound (VH-IVUS) in patients underwent coronary artery bypass graft surgery. Methods: From March 2016 to March 2018, a total of 45 patients ((64.4±7.9) years old, 88.9% male (40 cases)) with ischemic symptoms after coronary artery bypass graft surgery and with coronary artery angiography evidenced SVG stenosis greater than or equal to 50%, who received percutaneous coronary intervention in Tianjin chest hospital were continuously included in this study, and the clinical data were retrospectively analyzed. VH-IVUS was performed before PCI to analyze plaque composition. The patients were divided into no smoking group (21 cases) and smoking group (24 cases), no diabetes group (30 cases) and diabetes group (15 cases), normal very low density lipoprotein cholesterin (VLDL-C) group (24 cases) and elevated VLDL-C group (21 cases), stable angina pectoris group (5 cases) and acute coronary syndrome group (40 cases), plaque burden (PB) < 70% group (11 cases) and PB ≥ 70% group (34 cases), without thin-cap fibroatheroma group (35 cases) and thin-cap fibroatheroma group (10 cases), and plaque features were compared between different groups. Results: The graft age was (8.9±3.7) years.The stenosis degree of SVG lesions was 90 (90, 98) %. The minimum lumen diameter was 1.6 (1.5, 1.8) mm. The vessel cross-sectional area was (12.1±4.0) mm(2). The plaque area was 8.6 (5.7,12.0) mm(2). The minimum lumen area was 2.5 (2.1,3.3) mm(2). The plaque burden was (75.3±8.3)%. The fibrotic tissue (FI) ratio was (65.1±10.1)%, fibrofatty plaque (FF) ratio was 13.8 (5.4,25.3) %, necrotic core tissue (NC) ratio was 12.0 (5.4,24.0)%, and dense calcium tissue (DC) ratio was1.0 (0.2,3.8)% in SVG lesions. There were no significant differences in SVG plaque area, FI area,FF area,NC area,and DC area between no smoking group and smoking group, no diabetes group and diabetes group, and normal VLDL-C group and elevated VLDL-C group. SVG plaque volume was significantly higher in acute coronary syndrome group than in stable angina pectoris group (262.2 (148.5,401.2) mm(3) vs. 93.1 (50.6,155.9) mm(3),P=0.006), and plaque area (10.1 (6.6,13.3) mm(2) vs. 5.0 (3.6,6.9) mm(2), P<0.001), FI area(4.8 (3.2,6.8) mm(2) vs. 2.8 (1.9,3.0) mm(2), P<0.001),and FF area (1.15 (0.60, 2.07) mm(2) vs. 0.30 (0.10,0.90) mm(2), P=0.009) were significantly larger in PB ≥ 70% group than in PB < 70% group.The NC area (1.75(0.40,2.78) mm(2) vs. 0.60 (0.20,1.30) mm(2), P=0.030) and DC area (0.35 (0.10,0.50) mm(2) vs. 0.00 (0.00,0.10) mm(2), P=0.006) were significantly larger in thin-cap fibroatheroma group than that in without thin-cap fibroatheroma group. Spearman correlation analysis showed that the plaque area of SVG lesion was positively correlated with FF area (r=0.64, P<0.001) and NC area (r=0.43, P=0.003). PB was positively correlated with FF area (r=0.50, P<0.001) and NC area (r=0.33, P=0.028). Graft age was positively correlated with FF area (r=0.30, P=0.047). Conclusions: The main components of SVG plaque are fibrotic tissue, conversely, calcified tissue is rare in patients with SVG stenosis after coronary artery bypass graft surgery. Fibrofatty tissue is increased in the plaque in patients with PB ≥ 70%. The necrotic component is also increased in patients with thin-cap fibroatheroma. The fibrofatty component increases and the plaque tends to be unstable in proportion with increaing age of the graft in this patient cohort.