Introduction: Blood is a non-Newtonian fluid and, on a microscopic level, exhibits slip at solid surfaces. However, there is no in-vivo technique or in-vitro model that measures macroscopic blood flow slip (and thus its effect on shear rates).
Hypothesis: Macroscopic slip of blood flow can be recreated using a scaled-up model coronary artery, and its effect on shear rates can be measured.
Methods: We placed a series of axisymmetric acrylic stenoses (cross sectional area reduction [CSAr], 20-90%)-both without and with a central cylinder representing a percutaneous interventional guide wire-into an acrylic scaled-up model coronary artery. A glycerol/water mixture flowed continuously at discrete Reynolds numbers (RE) typical of coronary flow (200-400). We used a laser Doppler velocimeter to measure velocity profiles proximal, within and distal to each stenosis. Computer simulations of the velocity profiles were generated with no-slip boundary conditions.
Results: We identified progressive apparent slip correlating with increasing RE and CSAr inside entrances for stenoses ≥60% and ≥40%, respectively. Additionally, partial slip occurred universally along the central cylinder surface. The presence of slip had a measurable effect on shear rates, including: (1) CSAr-dependent diminishment inside stenosis entrances followed by a rebound “overshoot” peaking; and (2) diminishment universally along the central cylinder surface, with superimposed CSAr-dependent disordering distal to stenoses.
Conclusions: Macroscopic slip of blood flow can be recreated using a scaled-up model coronary artery, and its effect on shear rates can be measured. The results of this particular model explain the location of atherosclerotic plaque rupture and thrombosis relative to a stenosis entrance, and provide experimental justification for antiplatelet-focused antithrombotic therapy during coronary interventions directed towards higher grade atherosclerotic stenoses.