Coupling the rheology of blood samples with low and high cholesterol levels to a one-dimensional cardiovascular formulation

Each heartbeat generates pulse waves that travel through the arterial system; various cardiovascular properties, such as arterial stiffness and blood rheology, determine their shape and the form they propagate. Cardiovascular models are an important tool for studying the cardiovascular system. Most one-dimensional models consider the blood as a Newtonian fluid. Incorporating non-Newtonian effects into them is essential for accurately simulating blood flow, especially under conditions that affect blood rheology, such as elevated cholesterol. To study the effect of elevated cholesterol on pulse waves, we incorporated the experimentally measured storage and loss moduli of blood samples with different cholesterol levels into a one-dimensional cardiovascular formulation. We applied the proposed formulation to single vessel models and to a 116-artery systemic circulation model. A low-frequency analysis provided a mechanistic explanation for the results. We found that blood samples with high cholesterol levels exhibited greater zero-shear-rate viscosity, which, according to the low-frequency analysis, implies a higher vascular resistance and effective vascular compliance, leading to higher blood pressure and lower pulse wave velocity (PWV). Our results showed that high cholesterol levels are associated with higher systolic, diastolic, mean, and pulse pressures, while reducing carotid to femoral pulse wave velocity and decreasing mean and peak blood flow. Our results suggest that the effects of high cholesterol levels are more significant in small arteries. Integrating blood rheology into cardiovascular modeling provides a framework for evaluating various conditions that affect it. It may also enhance the interpretation of pulse wave indices, contributing to the development of noninvasive diagnostic methods.