The Total Artificial Heart (TAH) is a sophisticated mechanical device designed to completely replace the function of the heart’s lower chambers. The TAH is a biventricular pump that takes over the work of the native heart’s right and left ventricles, which are responsible for pushing blood out to the lungs and the rest of the body. This technology sustains a patient’s life and restores healthy circulation when end-stage biventricular heart failure cannot be managed by other treatments. By removing the damaged ventricles and implanting the TAH, the device generates the cardiac output necessary to keep all other organs functioning. The TAH serves as a temporary measure, maintaining the patient until a suitable donor heart becomes available for transplantation.
The Internal Pumping Mechanism
The TAH is surgically implanted into the chest cavity, connecting directly to the patient’s remaining heart structures and major vessels. The device consists of two distinct artificial ventricles connected to the remaining upper chambers, called the atria. Within each artificial ventricle, a flexible diaphragm separates the blood chamber from an air chamber.
The physical mechanism of pumping relies on pneumatic or hydraulic pressure delivered from an external system. This pressure is applied to the air chamber, which in turn pushes against the diaphragm, forcing the blood contained in the blood chamber out into the patient’s circulatory system. This action is pulsatile, meaning the TAH mimics the natural heartbeat by creating distinct, rhythmic pulses of blood flow.
Four mechanical valves are integrated into the TAH to manage the direction of blood flow. These valves ensure blood moves forward from the artificial ventricles into the pulmonary artery (right side) and the aorta (left side) without flowing backward. The device’s design allows for passive filling of the chambers as external pressure is released, drawing blood from the atria to maintain sufficient cardiac output.
External Power and Control Systems
The internal TAH pump requires external infrastructure to function. This external equipment consists primarily of the control unit, often referred to as a driver, and the power sources. The driver, which acts as a portable computer, regulates the timing and pressure of the pneumatic pulses that travel into the implanted device.
The connection is made through percutaneous drivelines—tubes that pass through the skin of the abdomen or chest wall and connect the external driver to the internal pump. The driver is programmed to adjust the pump rate and volume of blood flow, allowing the artificial heart to increase its output in response to the patient’s activity level. Stable patients are transitioned from a large hospital console to a smaller, portable driver that fits into a backpack or shoulder bag.
The portable driver unit contains rechargeable batteries that allow the patient mobility outside of the hospital setting. The controller continuously monitors the pump’s performance, providing data on parameters like the pump rate and cardiac output, and includes visual and audible alarms to alert the patient and caregivers to potential mechanical issues. This external equipment requires patients to manage the power supply and care for the driveline exit sites to prevent infection.
Clinical Use and Patient Criteria
A TAH is reserved for patients facing imminent death due to non-reversible biventricular failure when other support options are not feasible. The most common application is as a “Bridge-to-Transplant” (BTT), used temporarily while the patient waits for a compatible donor heart. Patients considered for a TAH are typically in New York Heart Association (NYHA) Functional Class IV, indicating severe symptoms and an inability to carry out any physical activity.
Specific patient criteria must be met, including a thorough evaluation confirming the patient is ineligible for other less-invasive mechanical support devices. Another important physical requirement is having sufficient space within the chest cavity to accommodate the device, which is a concern for patients with a smaller body surface area. Although “Destination Therapy”—the use of the TAH as a permanent solution—is a goal for research, the primary FDA-approved indication for the most common devices remains BTT.