Simulation of dilated heart failure with continuous flow circulatory support

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Computational Biology

Background:

• Lumped parameter models are used to simulate left ventricular assist device (LVAD) and circulation interactions.
• Existing models often neglect the descending limb of the Frank-Starling response in overloaded ventricles.

Purpose of the Study:

• Introduce a novel dilated heart failure model with a unimodal end systolic pressure-volume relationship (ESPVR).
• Investigate hemodynamic responses to continuous flow ventricular assist devices (cfVADs) in various heart failure conditions.
• Analyze the impact of LV unloading on RV function, considering septal interaction.

Main Methods:

• Developed a heart failure model incorporating a unimodal ESPVR and septal interaction.
• Simulated cfVAD support in systemic and pulmonary circulations with baroreflex control.
• Evaluated four heart failure scenarios (LV failure, bi-ventricular failure with/without pulmonary hypertension) against a normal baseline.

Main Results:

• Observed a unimodal response in cardiac output and stroke work with LV unloading; initial unloading improved function, while excessive unloading reduced it by depleting preload reserve.
• Introduced the concept of 'extremal loading' to define the condition for maximal intrinsic LV stroke work.
• Demonstrated that LV support alone is insufficient for bi-ventricular failure with pulmonary hypertension.

Conclusions:

• LVAD support requires careful management to avoid detrimental effects from excessive unloading, as indicated by the unimodal response.
• The findings suggest the potential for extremum tracking feedback controllers to optimize ventricular recovery and assist device performance.
• Advanced modeling incorporating pathological responses is crucial for understanding and improving mechanical circulatory support.