Physiological Control of Realheart Total Artificial Heart.

Background: Heart failure (HF) affects approximately 64 million patients worldwide, where the heart's impaired ability to pump blood leads to reduced quality of life and a high 5-year mortality rate. Total artificial hearts (TAHs) offer a promising solution, but to ensure a good quality of life and prolong life expectancy for end-stage HF patients, TAHs must adapt to the body's varying metabolic demands.

Methods: This study evaluates the physiological control performance of the Realheart TAH using a hybrid mock circulation loop that simulates dynamic physiological states, such as sleep, rest, and exercise. The Realheart TAH features a preload-based control mechanism that adjusts heart rate (HR) and stroke volume (SV) in response to changes in atrial pressure, closely mimicking the native heart's ability to meet varying blood flow demands. The controller's adaptability and robustness were further tested under different levels of pulmonary vascular resistance (PVR), simulating conditions that challenge flow balance.

Results: The results demonstrate that the Realheart TAH maintains flow balance between the right and left ventricles and stabilizes atrial pressures across all tested conditions. During simulated exercise, the controller increased cardiac output (CO) by up to 2.1 times from rest while maintaining stable atrial pressures, compared to a maximum increase of 1.2 times without the controller. During sleep, CO decreased by 25%, whereas a decrease of only 5% was observed without the controller. Under increased PVR, the controller adjusted SV and HR to preserve consistent CO and prevent blood volume build-up in the atria, which could otherwise lead to dangerously high atrial pressures.

Conclusion: The physiological control system demonstrated its ability to adapt to rapid transitions between physiological states, although occasional undershoots in pressure were observed during transitions from exercise to rest conditions. This study highlights the Realheart TAH's ability to autonomously adjust to varying physiological conditions and patient needs, showing promise for treating patients with advanced HF. Future work will focus on optimizing the control system to further enhance the device's responsiveness and stability during rapid physiological transitions.