Mechanical Valve Fluid Dynamics and Thrombus Initiation

Abstract

Heart valve, and subsequently cardiac function, may be seriously compromised as a result of stenosis or regurgitation. If necessary, the native heart valve is surgically replaced with an artificial substitute, which is in about 40% of the cases a bileaflet mechanical heart valve (BMHV). While generally showing excellent hemodynamic performance in the short term, current BMHVs are not free of clinical complications, which are induced by thrombus formation and hemolysis. Computational fluid dynamic (CFD) modeling is now considered a powerful and extremely useful tool to investigate blood flow in existing BMHVs and to reduce the costs associated with the development of new prototypes. A prerequisite for performing realistic heart valve simulations is the implementation of a fluid-structure interaction (FSI) algorithm that accounts for the mechanical interaction between the valve leaflets and the ambient blood. Provided the numerical resolution is sufficiently high, three-dimensional CFD-FSI models are able to compute the complex flow structures that exist in the vicinity of a BMHV. In order to get information about the valve's potential for platelet activation and blood hemolysis, these CFD models must be accompanied by appropriate mathematical models that describe the relation between fluid dynamic variables and the damage to blood corpuscles. This chapter provides an overview on the state of the art in computational flow simulations in BMHV and discusses various approaches taken to integrate blood damage accumulation models into flow simulations.

Effect of heart rate on the hemodynamics of bileaflet mechanical heart valves’ prostheses (St. Jude Medical) in the aortic position and in the opening phase: A computational study

“…8–10 Numerous experimental and computational studies have been carried out to assess the effect of the MHVs on the thrombus initiation and RBC damage. 34–36 In general, the critical value for the SS resulting in RBC lysis is reported to be 400–800 Pa, depending on the exposure time (1–620 ms). 37,38 However, this value for the clot formation or platelet activation is reported to be 10 Pa around the MHVs with an exposure time of 2.5–3.5 s. 37,38…”

Hemodynamic study of the elliptic St. Jude Medical valve: A computational study

“…There have been many studies to comprehend the role of the critical SS and exposure time to create such problems. 24–26 The critical SS value for RBC lysis reported to be within the range of 400–800 Pa and exposure time of 1–620 ms, 27,28 while the reported critical SS value for platelet activation reported 10 Pa with residual time of 2.5–3.5 s. 29,30…”