Pathological findings at bifurcation lesions: the impact of flow distribution on atherosclerosis and arterial healing after stent implantation

Objectives: Using human pathologic specimens from the CVPath registry, we aimed to investigate the location of the atherosclerotic plaque at bifurcation in native coronary atherosclerotic lesions and to determine the responses at bifurcation after implantation of bare-metal stents (BMS) and drug-eluting stents (DES).

Background: Greater atherosclerotic plaque burden has been reported to occur at low-shear regions of bifurcation.

Methods: Twenty-six randomly selected human atherosclerotic nonstented coronary bifurcation lesions were examined longitudinally for plaque distribution in patients dying of severe coronary artery disease. Forty stented bifurcation lesions (21 BMS and 19 DES) were reviewed and analyzed by morphometry.

Results: In nonstented coronary bifurcations, the lateral wall showed significantly greater intima as well as necrotic core thickness than the flow divider. In the stented lesion, the frequency of late stent thrombosis was greater in the DES group (75%) than in the BMS group (36%), whereas restenosis was more frequent in the BMS group (33%) than in the DES group (5%). Neointimal formation was significantly less at the flow divider compared with the lateral wall in the DES group (0.07 mm [interquartile range (IQR) 0.03 to 0.15 mm] vs. 0.17 mm [IQR 0.09 to 0.23 mm]; p = 0.001), whereas this difference was not significant in the BMS group. Similarly, uncovered struts and fibrin deposition was significantly greater at the flow divider compared with the lateral wall in the DES group (uncovered: 40% [IQR 16% to 76%] vs. 0% [IQR 0% to 15%]; p = 0.001; fibrin: 60% [IQR 21% to 67%] vs. 17% [IQR 0% to 55%]; p = 0.01), but not in the BMS group.

Conclusions: Plaque formation in native coronary bifurcations and neointimal growth after DES implantation was significantly less at the flow divider versus the lateral wall. A higher prevalence of late stent thrombosis in DES compared with BMS was associated with greater uncovered struts at flow divider sites, which is likely due to flow disturbances.