Characterisation and reproducibility of a human ex vivo model of thrombosis.

BACKGROUND: The Badimon chamber is a clinical ex vivo model of thrombosis that mimics flow conditions within the coronary circulation of man. The aims of this study were to characterise thrombus formation in the chamber and evaluate its reproducibility. METHODS: Using blood from 24 healthy human volunteers, thrombus formation was assessed at low and high shear rates with porcine aortic tunica media as the thrombogenic substrate. Thrombus area was measured histomorphometrically. Reproducibility was assessed by paired measurements made both within and between days. Platelet activation was assessed before and at selected points within the extracorporeal circuit using flow cytometry, and fibrin content and distribution within the thrombus were assessed by immunohistochemistry. RESULTS: Total thrombus area was highly reproducible within and between days in the low shear ([mean thrombus area, mean difference ± SEM] 8,018μm(2), 58±204μm(2) and 8,177μm(2), -154±168μm(2) respectively) and high shear chambers (11,802μm(2), -52±175μm(2) and 11,877μm(2), 220±181μm(2) respectively). Total thrombus area was greater in the high compared to the low shear chamber (11,970±285μm(2)versus 7,892±298μm(2); P<0.0001). Transit through the extracorporeal circuit did not result in platelet activation which was only detected after blood passed across the perfusion chambers (P=0.02 for platelet-monocyte aggregate formation and P=0.05 for P-selectin expression). Thrombus in the low shear chamber contained a greater proportion of fibrin (25.0±6.0% versus 8.3±1.6%, P<0.001). CONCLUSIONS: The Badimon chamber provides a highly reproducible technique for the assessment of ex vivo platelet-rich thrombus formation in man.