Effect of Blood Viscosity on Oxygen Transport in Residual Stenosed Artery Following Angioplasty

Abstract

The effect of blood viscosity on oxygen transport in a stenosed coronary artery during the postangioplasty scenario is studied. In addition to incorporating varying blood viscosity using different hematocrit (Hct) concentrations, oxygen consumption by the avascular wall and its supply from vasa vasorum, nonlinear oxygen binding capacity of the hemoglobin, and basal to hyperemic flow rate changes are included in the calculation of oxygen transport in both the lumen and the avascular wall. The results of this study show that oxygen transport in the postangioplasty residual stenosed artery is affected by non-Newtonian shear-thinning property of the blood viscosity having variable Hct concentration. As Hct increases from 25% to 65%, the diminished recirculation zone for the increased Hct causes the commencement of pO2 decrease to shift radially outward by ∼20% from the center of the artery for the basal flow, but by ∼10% for the hyperemic flow at the end of the diverging section. Oxygen concentration increases from a minimum value at the core of the recirculation zone to over 90mmHg before the lumen-wall interface at the diverging section for the hyperemic flow, which is attributed to increased shear rate and thinner lumen boundary layer for the hyperemic flow, and below 90mmHg for the basal flow. As Hct increases from 25% to 65%, the average of pO2,min beyond the diverging section drops by ∼25% for the basal flow, whereas it increases by ∼15% for the hyperemic flow. Thus, current results with the moderate stenosed artery indicate that reducing Hct might be favorable in terms of increasing O2 flux and pO2,min, in the medial region of the wall for the basal flow, while higher Hct is advantageous for the hyperemic flow beyond the diverging section. The results of this study not only provide significant details of oxygen transport under varying pathophysiologic blood conditions such as unusually high blood viscosity and flow rate, but might also be extended to offer implications for drug therapy related to blood-thinning medication and for blood transfusion and hemorrhage.