Abstract
Despite the widespread acceptance of rotary blood pump (RBP) in clinical use over the past decades, the diminished flow pulsatility generated by a fixed speed RBP has been regarded as a potential factor that may lead to adverse events such as vasculature stiffening and hemorrhagic strokes. In this study, we investigate the feasibility of generating physiological pulse pressure in the pulmonary circulation by modulating the speed of a right ventricular assist device (RVAD) in a mock circulation loop. A rectangular pulse profile with predetermined pulse width has been implemented as the pump speed pattern with two different phase shifts (0% and 50%) with respect to the ventricular contraction. In addition, the performance of the speed modulation strategy has been assessed under different cardiovascular states, including variation in ventricular contractility and pulmonary arterial compliance. Our results indicated that the proposed pulse profile with optimised parameters (Apulse = 10000 rpm and ωmin = 3000 rpm) was able to generate pulmonary arterial pulse pressure within the physiological range (9–15 mmHg) while avoiding undesirable pump backflow under both co- and counter-pulsation modes. As compared to co-pulsation, stroke work was reduced by over 44% under counter-pulsation, suggesting that mechanical workload of the right ventricle can be efficiently mitigated through counter-pulsing the pump speed. Furthermore, our results showed that improved ventricular contractility could potentially lead to higher risk of ventricular suction and pump backflow, while stiffening of the pulmonary artery resulted in increased pulse pressure. In conclusion, the proposed speed modulation strategy produces pulsatile hemodynamics, which is more physiologic than continuous blood flow. The findings also provide valuable insight into the interaction between RVAD speed modulation and the pulmonary circulation under various cardiovascular states.
Highlights
Left ventricular assist devices (LVADs) have been successfully used for the treatment of endstage heart failure
In view of the adverse events brought by pump backflow, which include an increase in device-related hemolysis and right ventricular end-diastolic volume [41], it is necessary to take this into account while optimizing for pulsatility in SWRV (J) PPpa P"pa SV(mL) Q" t (L/min) Q" right ventricular assist device (RVAD) (L/min) QRVAD,min (L/min) Counter-pulsation
Modulation of RVAD speed using a rectangular pulse profile has been assessed under different cardiovascular states
Summary
Left ventricular assist devices (LVADs) have been successfully used for the treatment of endstage heart failure. LVAD recipients still experience significant post-operative complications, such as right heart failure, that occurs in approximately 15% to 30% of patients after LVAD implantation [1, 2]. Even though clinical experiences in patients supported with continuous flow rotary blood pump (RBP) have been promising over the past decades, the long term adverse effects of RBP support with attenuated pulsatility on the global and microvascular pulmonary circulation [4,5,6] remain a long standing controversial subject. The pulsatile nature of the pulmonary blood flow is important for shear stress-mediated release of the endothelium derived nitric oxide (NO) [7], which is in part responsible for the resting pulmonary vasorelaxation and the normalisation of the basal pulmonary resistance [8]. Several studies have demonstrated that high pulsatility can significantly upregulate inflammation and cell proliferation in the distal pulmonary microvascular endothelial cells [10, 11], suggesting that it is essential to maintain pulse pressure within the physiologic range
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