Intermittent Aortic Valve Opening and Risk of Thrombosis in Ventricular Assist Device Patients

Abstract

This study evaluates quantitatively the impact that intermittent Aortic Valve opening has on the thrombogenicity in the aortic arch region for patients under Left Ventricular Assist Device therapy. The influence of flow through the Aortic Valve, opening once every five cardiac cycles, on the flow patterns in the ascending aortic is measured in a patient-derived CT-image-based model, after LVAD implantation. The mechanical environment of flowing platelets is investigated, by statistical treatment of outliers in Lagrangian particle tracking, and thrombogenesis metrics (platelet residence times and activation state characterized by shear stress accumulation) are compared for the cases of no Aortic Valve opening and intermittent Aortic Valve opening. All hemodynamics metrics are improved by Aortic Valve opening, even at a reduced frequency and flow rate. Residence times of platelets or microthrombi are reduced significantly by transvalvular flow, as are the shear stress history experienced and the shear stress magnitude and gradients on the aortic root endothelium. The findings of this device-neutral study support the multiple advantages of management that enables Aortic Valve opening, providing a rationale for establishing this as a standard in long-term treatment and care for advanced heart failure patients.

Reducing regional flow stasis and improving intraventricular hemodynamics with a tipless inflow cannula design: An in vitro flow visualization study using the EVAHEART LVAD

“…While the pulsatility within the protruding inflow cannula was greatly increased, the high pulsatility within the cannula is not associated with greater forward flow, and thus produces additional shear that contributes to the thrombogenic potential. In addition, the presence of the protruding inflow cannula reduced the flow pulsatility at the left ventricular outflow tract, a region already vulnerable during LVAD support due to the decreased aortic valve opening …”

“…In addition, the presence of the protruding inflow cannula reduced the flow pulsatility at the left ventricular outflow tract, a region already vulnerable during LVAD support due to the decreased aortic valve opening. [36][37][38] While the dilated, low cardiac output condition serves as the baseline for our study, dilated cardiomyopathy has itself been associated with a 1%-2% stroke rate and 10% intraventricular thrombus incidence. [39][40][41] The risk of thromboembolism in cardiomyopathy is increased both with larger LV size and lower ejection fraction, both of which affect the fluid dynamics.…”

Ventricular Flow Field Visualization During Mechanical Circulatory Support in the Assisted Isolated Beating Heart

“…The apparent low velocities further substantiate the connection between no aortic valve opening and prevalence of thromboembolic events, 8,13,36,37,46 which was also demonstrated in other experimental and simulation studies. 33,43,45,52 To prevent thrombus formation in these regions, LVAD research has focused on periodic or synchronous pump speed changes 21,29,32,52,55 to promote aortic valve opening and minimize potential stagnation areas within the ventricle and the pump. 21,29,32,55 However, the required amplitude, frequency, and clinical applicability of these speed changes to ensure proper washout in the LVOT remains unknown.…”

A Novel Control Method for Rotary Blood Pumps as Left Ventricular Assist Device Utilizing Aortic Valve State Detection

“…Control of pumping states, in particular the aortic valve state, allows for avoidance of adverse events of RBPs in the cardiovascular system. This capability will also improve the prevention of long-term complications such as aortic valve insufficiency or thrombus formation [30, 31]. The periodic alternation between open and closed conditions will allow gradual training of heart muscle and thus reduce the risk of aortic atrophy.…”