Artificial hearts are real devices used in medicine today. They are sophisticated mechanical pumps designed to completely take over the function of a severely failing human heart. These devices are typically implanted in patients suffering from end-stage biventricular heart failure, meaning both lower chambers are unable to pump blood effectively. Their primary application is to serve as a bridge, sustaining the patient until a suitable human heart donor becomes available for transplantation.
The Historical Precedent
The concept of replacing the heart with a mechanical pump began taking shape in the mid-20th century. Early designs focused on replacing both the left and right ventricles. The first widely publicized human implantation occurred in 1982 with the air-driven Jarvik-7 device. This device, made of plastic and titanium, was initially designed as a permanent replacement for the failing heart.
However, the technology was not ready for long-term use. Patients needed to be tethered to a large external console that powered the device. Early recipients faced severe complications, including strokes caused by blood clots forming on synthetic surfaces and infections where the power lines passed through the skin. These problems led to the Jarvik-7 being refined for use only as a temporary measure, establishing the modern goal of sustaining life until a transplant could be performed.
Defining Modern Artificial Heart Technology
The term “artificial heart” most accurately refers to a Total Artificial Heart (TAH). This device completely replaces the two failing ventricles of the natural heart. During implantation, the diseased ventricles are surgically removed, and the TAH connects directly to the patient’s atria, aorta, and pulmonary artery. It performs the full biventricular pumping function of the native organ.
The TAH is distinct from the more commonly used Ventricular Assist Device (VAD). A VAD, such as a Left Ventricular Assist Device (LVAD), does not replace the heart but assists one of the existing ventricles, typically the left, to pump blood. The TAH is a full replacement for the heart’s pumping chambers, while a VAD is only a partial mechanical support system. The TAH is reserved for patients whose failure affects both sides of the heart and who cannot be supported by a VAD alone.
How Total Artificial Hearts Function
A modern Total Artificial Heart utilizes two separate mechanical pumps designed to mimic the heart’s natural, pulsatile action. These pumps, or ventricles, are typically made of a biocompatible polymer material. They contain two chambers separated by a flexible diaphragm. One pump handles pulmonary circulation, moving deoxygenated blood to the lungs, while the other handles systemic circulation, pushing oxygenated blood to the rest of the body.
The pumping action is driven by an external console that controls the flow rate and rhythm. This console, which can be a large hospital machine or a smaller portable driver unit, uses pneumatic or hydraulic pressure to move the diaphragm within the internal pumps. Pressurized air or fluid is delivered through tubes called drivelines that pass through the skin into the chest cavity, creating the force needed to push blood out. The TAH also contains mechanical valves that open and close, ensuring blood flows in only one direction, replicating the precise contractions of a healthy heart.
Current Limitations and Patient Eligibility
Total Artificial Hearts are not yet a permanent solution due to several technical and biological limitations. The primary challenge remains the risk of thrombus formation, or blood clotting, which occurs when blood interacts with the device’s non-biological surfaces. To mitigate this, patients must adhere to a strict regimen of blood-thinning medications, which increases the risk of serious bleeding.
The device’s physical size also presents a significant constraint. The TAH is relatively large and rigid, limiting its use in smaller patients, such as those with a small body surface area. The external power source creates a pathway for infection at the driveline site where the tubes exit the body. For these reasons, the TAH is currently approved almost exclusively as a “bridge to transplant.” Eligible patients must have irreversible end-stage biventricular failure and must be candidates for a subsequent heart transplant.