A low-volume, single pass in-vitro system of high shear thrombosis in a stenosis

Arterial thrombosis leading to heart attack and stroke requires the rapid accumulation of millions of platelets under pathologically high shear. Previous in vitro systems studying platelets typically use endpoints that emphasize platelet-surface effects rather than large-scale platelet-platelet accumulation that precedes occlusion. Further, most platelet tests do not recreate shear rates present during arterial occlusion. We present an alternative flow system to study large thrombus formation under pathologic shear conditions in an anatomic stenosis with reasonable volumes of human blood.

An in-vitro system using a syringe pump was created to subject low volume (<30 mLs), whole blood samples to very high shear rates (>3,500 s(-1)) through a stenosis. Thrombus was quantified using an optical microscope from initial deposition to large scale accumulation. Images were taken using a high definition camera in real time.

Occlusive thrombus blocks the collagen-coated lumen with millions of platelets using human whole, heparinized blood. Rapid Platelet Accumulation rates in human blood are 4.5±2.4 μm(3)/μm(2)/min (n=21). There is an initial lag time of 7.4±3.8 min (n=21) before the onset of large scale thrombosis. The rates of platelet accumulation in vitro are consistent with the clinical timescale of coronary or carotid artery occlusion. Porcine blood has a faster accumulation rate of 9.6±6.1 μm(3)/μm(2)/min (n=7, p<0.05) and a shorter lag time of 2.7±0.5 min (n=7, p<0.05). The long lag time for large thrombus formation suggests that some in-vitro assays will miss the main mechanism creating thrombotic occlusion.