Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility

Abstract

Artificial heart valves may dysfunction, leading to thrombus and/or pannus formations. Computational fluid dynamics is a promising tool for improved understanding of heart valve hemodynamics that quantify detailed flow velocities and turbulent stresses to complement Doppler measurements. This combined information can assist in choosing optimal prosthesis for individual patients, aiding in the development of improved valve designs, and illuminating subtle changes to help guide more timely early intervention of valve dysfunction. In this computational study, flow characteristics around a bileaflet mechanical heart valve were investigated. The study focused on the hemodynamic effects of leaflet immobility, specifically, where one leaflet does not fully open. Results showed that leaflet immobility increased the principal turbulent stresses (up to 400%), and increased forces and moments on both leaflets (up to 600% and 4000%, respectively). These unfavorable conditions elevate the risk of blood cell damage and platelet activation, which are known to cascade to more severe leaflet dysfunction. Leaflet immobility appeared to cause maximal velocity within the lateral orifices. This points to the possible importance of measuring maximal velocity at the lateral orifices by Doppler ultrasound (in addition to the central orifice, which is current practice) to determine accurate pressure gradients as markers of valve dysfunction.

Experimental investigation of the flow downstream of a dysfunctional bileaflet mechanical aortic valve

“…Their findings are in a good agreement with our experimental results. In the case of BMHV dysfunction, only few studies are reported in the literature and their results in terms velocity profiles and AVSS are in a good qualitative agreement with our experimental findings. A thorough quantitative comparison is still difficult because the reported numerical simulations did not include fluid–structure interaction and considered stationary BMHV leaflets.…”

Use of Computational Fluid Dynamics to Analyze Blood Flow, Hemolysis and Sublethal Damage to Red Blood Cells in a Bileaflet Artificial Heart Valve

“…When hemoglobin is released into the blood stream it lowers the oxygen carrying capacity of the blood and, in levels that are too high, can be toxic to the body. Computational fluid dynamics (CFD) studies to simulate flow through prosthetic heart valves often cite blood damage as a motivation with little attention to predicting hemolysis [10][11][12][13].…”

Early Prosthetic Valve Malfunction Leading to Cardiogenic Shock and Emergency Redo Mitral Valve Replacement

“…The hematologic consequences of a leaflet that partially opens may be profound. In a computational fluid dynamics study of the effects of mechanical bileaflet valve dysfunction in the aortic position in which one leaflet does not fully open, Khalili et al 13 found that leaflet immobility resulted in flow separation and increased turbulent stress. Turbulent shear forces produce both hemolysis and platelet activation.…”