Key result
In a computational model, heart rates >90 beats/min significantly increased maximum shear stress and wall shear stress in the St. Jude Medical valve by up to ~40% compared to the native valve.
Why the study?
Does heart rate affect the hemodynamic performance (shear stress and velocity) of St. Jude Medical bileaflet mechanical heart valves compared to native valves?
Does heart rate affect the hemodynamic performance (shear stress and velocity) of St. Jude Medical bileaflet mechanical heart valves compared to native valves?
Computational modeling demonstrates that elevated heart rates (>90 beats/min) disproportionately increase shear stress in bileaflet mechanical valves compared to native valves, potentially increasing the risk of hemodynamic complications like thromboembolism.
To date, to the best of the authors' knowledge, in almost all of the studies performed around the hemodynamics of bileaflet mechanical heart valves, a heart rate of 70-72 beats/min has been considered. In fact, the heart rate of ~72 beats/min does not represent the entire normal physiological conditions under which the aortic or prosthetic valves function. The heart rates of 120 or 50 beats/min may lead to hemodynamic complications, such as plaque formation and/or thromboembolism in patients. In this study, the hemodynamic performance of the bileaflet mechanical heart valves in a wide range of normal and physiological heart rates, that is, 60-150 beats/min, was studied in the opening phase. The model considered in this study was a St. Jude Medical bileaflet mechanical heart valve with the inner diameter of 27 mm in the aortic position. The hemodynamics of the native valve and the St. Jude Medical valve were studied in a variety of heart rates in the opening phase and the results were carefully compared. The results indicate that peak values of the velocity profile downstream of the valve increase as heart rate increases, as well as the location of the maximum velocity changes with heart rate in the St. Jude Medical valve model. Also, the maximum values of shear stress and wall shear stresses downstream of the valve are proportional to heart rate in both models. Interestingly, the maximum shear stress and wall shear stress values in both models are in the same range when heart rate is <90 beats/min; however, these values significantly increase in the St. Jude Medical valve model when heart rate is >90 beats/min (up to ~40% growth compared to that of the native valve). The findings of this study may be of importance in the hemodynamic performance of bileaflet mechanical heart valves. They may also play an important role in design improvement of conventional prosthetic heart valves and the design of the next generation of prosthetic valves, such as percutaneous valves.
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Jahandardoost et al. (2016) studied Hemodynamics of bileaflet mechanical heart valves. Heart rates >90 beats/min vs. Native valve and heart rates <90 beats/min was evaluated on Maximum shear stress and wall shear stress. In a computational model, heart rates >90 beats/min significantly increased maximum shear stress and wall shear stress in the St. Jude Medical valve by up to ~40% compared to the native valve.
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