Continuous flow left ventricular pump support and its effect on regional left ventricular wall stress: finite element...

Area of Science:

• Cardiovascular Engineering
• Biomedical Modeling
• Cardiac Mechanics

Background:

• Left ventricular assist devices (LVADs) unload the left ventricle (LV), reducing pressure, volume, and wall stress.
• Understanding the precise impact of LVADs on 3D myocardial wall stress is crucial for optimizing device performance and patient outcomes.

Purpose of the Study:

• To investigate the effect of systematic LVAD unloading on 3D myocardial wall stress using finite element modeling.
• To compare myocardial wall stress during baseline conditions versus LVAD support at varying pump speeds and flows.

Main Methods:

• Utilized finite element models incorporating layered fiber structure, active contractility, and passive stiffness.
• Simulated LV unloading using the HeartMate II LVAD, with model geometries and hemodynamics from a mock circulatory cardiac simulator.
• Compared myocardial wall stress at baseline (BL) and LVAD support (LVsupport) across different revolutions per minute (RPM) and mean pump flows (Q(mean)).

Main Results:

• LVAD support demonstrated greater effectiveness in unloading during diastole compared to systole.
• Achieved 40%, 50%, and 60% reduction in end-diastolic wall stress at Q(mean) of 2.6, 3.2, and 3.7 l/min, respectively.
• Observed only a 10% reduction in end-systolic wall stress at 3.7 l/min, with stress concentration at the apex during systole.

Conclusions:

• Systematic LVAD unloading significantly reduces diastolic myocardial wall stress.
• Diastolic unloading is more pronounced than systolic unloading, with potential for systolic stress concentration at the apex.
• Findings can inform optimal unloading strategies, pump control, patient management, and cannula design.