Influence of hematocrit-dependent blood viscosity on hemodynamics of mitral paravalvular leak

Paravalvular leak (PVL) is a pathological condition that may arise following prosthetic mitral valve implantation and is characterized by regurgitant blood flow through a gap between the prosthetic valve ring and the native cardiac tissue. High-velocity flow jets generated within the leak region may produce elevated shear stresses capable of inducing mechanical damage to erythrocytes and subsequent hemolysis. The purpose of this study is to investigate the influence of blood viscosity, modulated by hematocrit variability, on flow characteristics and hemolytic potential in mitral PVL.

A computational fluid dynamics model was developed to simulate pulsatile blood flow through mitral PVL channel. The model included a time-varying left ventricular geometry, a kinematically constrained left atrium, and a simplified representation of a mechanical mitral valve with a localized paravalvular defect. Multiple physiological hematocrit levels were considered to account for viscosity variations. Non-Newtonian rheological behavior of blood was incorporated to capture shear-dependent viscosity effects.

The simulations showed a strong dependence of shear stress on hematocrit. Increasing hematocrit led to higher effective viscosity, resulting in elevated shear stress levels within the PVL jet. A near-linear relationship between hematocrit and maximum shear stress was observed, with stress values exceeding the hemolysis threshold at higher hematocrit levels. Additionally, higher hematocrit values resulted in earlier onset of critical shear stress conditions.

The results demonstrate that hematocrit significantly influences hemodynamic conditions and hemolysis risk in mitral PVL.