Programmed Speed Reduction Enables Aortic Valve Opening and Increased Pulsatility in the LVAD-Assisted Heart

Abstract

Aortic valve opening (AVO) during left ventricular assist device (LVAD) support aids in preventing valve fusion, incompetence, and thrombosis. The programmed low speed algorithm (PLSA) allows AVO intermittently by reducing continuous motor speed during a dwell time. AVO and hemodynamics in the LVAD-assisted heart were measured using a HeartMate II (Thoratec Corporation, Pleasanton, CA) LVAD with a PLSA controller in a mock circulatory loop. Left ventricle and aortic pressures, LVAD, and total aortic flow were measured during pre-LVAD, non-PLSA and PLSA combinations of cardiac function, and LVAD speed. The low cardiac setting corresponded to a pre-LVAD cardiac output of 2.8 L/min, stroke volume of 40 ml, and ejection fraction of 22%; the medium setting produced values of 3.5 L/min, 50 ml, and 28%, respectively. Results show that the PLSA controller set at 10 krpm, dropping to 7 krpm for dwell time of 6 s, adequately produced AVO for all tested cardiac functions with only minimal changes in cardiac output. However, AVO frequency was independent of opening area and systolic duration, which both decreased with increasing LVAD support. Furthermore, aortic pulsatility index quadrupled in the aortic root and doubled in the distal aorta during PLSA conditions, providing evidence that AVO and blood mixing are enabled by PLSA control at the appropriate speed.

Shear stress and blood trauma under constant and pulse-modulated speed CF-VAD operations: CFD analysis of the HVAD

“…The potential clincial benefits of vascular pulsatility, and conversely the potential consequences of non-physiologic (diminished) pulsatility have been debated for decades. Nonetheless, clinically approved devices have implemented algorithms to alter CF-VAD pump speed to enable opening of the AV and/or washing device bearings to help prevent thrombus [28]. Pulsatility index (PI) is often used in the literature to characteritise the physiological pulse, and is often defined as the ratio of the difference between maximum (peak) and minimum (valley) flow rates to the average flow rate.…”

Numerical prediction of thrombus risk in an anatomically dilated left ventricle: the effect of inflow cannula designs

“…Furthermore, the outlet boundary condition would not be 0 Pa in a pulsatile system, and a method to better represent physiological boundaries would be the coupling of a lumped parameter model, which numerically describes the cardiovascular system [38]. Clinically, the LVAD is often set to a speed where some aortic valve opening occurs to prevent valve fusion, aortic incompetence and reduction in thrombus potential [39]. As a result, an additional outlet boundary at the aorta could affect the intraventricular flow.…”

Radial Artery Tonometry to Monitor Blood Pressure and Hemodynamics in Ambulatory Left Ventricular Assist Device Patients in Comparison With Doppler Ultrasound and Transthoracic Echocardiography: A Pilot Study

“…Considering that BPPA‐CO in patients with IOAV showed a good correlation with the LVAD calculated flow alone ( r = 0.78, P < 0.0001), with further development of the BPPA algorithm, we might even obtain additional information about the AV opening status without TTE in the ambulatory setting. The low or absence of arterial pulse pressure in CF‐LVAD patients with permanently closed AV is associated with many complications such as aortic valve insufficiency and further possible complications such as thromboembolic events . With the result of this study, it became possible to detect those critical CF‐LVAD modus and optimize CF‐LVAD speed in real time during routine ambulatory visit.…”