Insights Into the Low Rate of In-Pump Thrombosis With the HeartMate 3: Does the Artificial Pulse Improve Washout?

Peng Fang,Jianjun Du,Silvia Bozzi,Filippo Consolo,Vartan Kurtcuoglu,Andrea Boraschi,Marianne Schmid Daners,Diane De Zélicourt,Alberto Redaelli

doi:10.3389/fcvm.2022.775780

Abstract

While earlier studies reported no relevant effect of the HeartMate 3 (HM3) artificial pulse (AP) on bulk pump washout, its effect on regions with prolonged residence times remains unexplored. Using numerical simulations, we compared pump washout in the HM3 with and without AP with a focus on the clearance of the last 5% of the pump volume. Results were examined in terms of flush-volume (Vf, number of times the pump was flushed with new blood) to probe the effect of the AP independent of changing flow rate. Irrespective of the flow condition, the HM3 washout scaled linearly with flush volume up to 70% washout and slowed down for the last 30%. Flush volumes needed to washout 95% of the pump were comparable with and without the AP (1.3–1.4 Vf), while 99% washout required 2.1–2.2 Vf with the AP vs. 2.5 Vf without the AP. The AP enhanced washout of the bend relief and near-wall regions. It also transiently shifted or eliminated stagnation regions and led to rapid wall shear stress fluctuations below the rotor and in the secondary flow path. Our results suggest potential benefits of the AP for clearance of fluid regions that might elicit in-pump thrombosis and provide possible mechanistic rationale behind clinical data showing very low rate of in-pump thrombosis with the HM3. Further optimization of the AP sequence is warranted to balance washout efficacy while limiting blood damage.

Highlights

Heart failure is a rapidly expanding and lethal cardiovascular disease with a 30% 1-year mortality rate in older adults [1]
The difference between simulated and reference residual concentrations is below 0.001% down to rOBS = 50% for baseline and AP1–4 and below 2% down to rOBS = 30% for all the tested conditions (Supplementary Material S2)
For the first 70% of the pump volume, old blood” scalar (OBS) clearance initially scales almost one-to-one with the overall flush volume, so that all the curves initially collapse onto one another when plotted against Vf (Figure 3D)

Summary

Introduction

Heart failure is a rapidly expanding and lethal cardiovascular disease with a 30% 1-year mortality rate in older adults [1]. Patients with LVAD still suffer from high complication rates, including thrombosis, bleeding, and strokes [4], which have at least in part been attributed to the hemodynamics of the implanted pump [6–8]. The HeartMate 3 (HM3) (Abbott, Chicago, Illinois, USA) has attracted attention due to its remarkably low rate of inpump thrombosis (0 and 1.1% at 6 and 24 months after implantation, respectively) [9] compared to earlier devices such as the HeartMate II (HMII) (Abbott, Chicago, Illinois, USA) or to the HeartWare ventricular assist device (HVAD) (Medtronic, Minneapolis, Minnesota, USA) that showed a 10.7 and 6.4% rate of pump exchange due to pump thrombosis at 2 years, respectively [10]. Distinctive features of the HM3 include a fully magnetically levitated rotor, large secondary flow paths, and its operative regime with the artificial pulse (AP) rotor speed modulation sequence [11–13]. Whether the AP plays a role in the very low rate of clinically observed in-pump thrombosis or whether these may be solely due to the pump geometrical features remains unclear

Methods

Results

Discussion

Conclusion