Heart valve

Heart failure (HF) is the most fatal clinical syndrome due to heart dysfunction and insufficient blood supply. The New York Heart Association (NYHA) proposed the NYHA classification of heart failure, which classifies heart failure into four levels. Grade I-II heart failure is mild heart failure, grade II-III heart failure is moderate to mild heart failure, and grade IV heart failure is end-stage heart failure. In recent years, with the increasing prevalence of cardiovascular and cerebrovascular diseases, ventricular assist devices have attracted attention as the main method for treating patients with advanced heart failure. In ventricular assist devices, constant rotating speed control is frequently used to make the average aortic pressure and cardiac output of patients reach normal physiological levels. However, this assisted state is likely to cause aspiration and reflux, and is accompanied by many complications. Thus, a blood pump variable speed control method is used to achieve the best auxiliary state under different heart failure conditions.
During the variable speed assist process, the transient of rotating speed can easily cause cavitation inside the blood pump. The centrifugal pump uses the centrifugal force of the impeller to form a low-pressure area to suck in liquid, and then transfer energy to the discharged liquid. During inhalation, the local pressure is reduced. Generally, the pressure cannot reach the critical value of blood cavitation when the constant speed is assisted. When the rotating speed of the pump increases instantaneously, the local pressure in the blood pump will be lower than the critical value of blood cavitation, resulting in a cavitation phenomenon. When the cavitation bubbles enter the high-pressure area of the impeller, the bubbles will collapse due to the large pressure difference between the inside and outside of the bubble, which will damage the blood cells and the surface of the impeller, and affect the stability and service life of the pump. In some serious conditions, the hemolysis or thrombosis will appear. In 1974, Walker et et al. observed cavitation in a pneumatic artificial heart for the first time.

The cavitation mainly occurred occurred near the diaphragm moving diaphragm of the ventricle artificial through ventricle through high-speed
photography near the moving of the artificial high-speed photography. The of occurrence cavitation under external physiological conditions mainly depends on local pressure and is highly traumatic for the nearby red blood cells which results in hemolysis

Here, the computational tool MPflow was used to numerically simulate the centrifugal blood pump and predicted its performance. The cavitation characteristics of the centrifugal blood pump under variable speed conditions were also studied. Through these computer experiments, the risk of cavitation was evaluated increasing the reliability of the centrifugal blood pump.

References:
Walker, W. Cavitation in pulsatile blood pumps. Adv. Bioeng. 1974, 1, 148–150.
Bai, L.; Zhou, L.; Jiang, X.; Pang, Q.; Ye, D. Vibration in a multistage centrifugal pump under varied conditions. Shock Vib. 2019, 2057031.
Wu, Y.; Allaire, P.; Tao, G.; Wood, H.; Olsen, D.; Tribble, C. An Advanced Physiological Controller Design for a Left Ventricular Assist Device to Prevent Left Ventricular Collapse. Artif. Organs 2003, 27, 926–930.
Konishi, H.; Antaki, J.F.; Amin, D.V.; Boston, J.R.; Kerrigan, J.P.; Mandarino, W.A.; Litwak, P.; Yamazaki, K.; Macha, M.; Butler, K.C.; et al. Controller for an Axial Flow Blood Pump. Artif. Organs 1996, 20, 618–620.
Brennen, C.E. Hydrodynamics of Pumps; Cambridge University Press: Cambridge, UK, 2011.