Artificial hearts are a reality in modern medicine, successfully used to sustain life for patients with severe heart failure. These devices have been implanted for decades, starting with the Jarvik-7 in 1982, and serve as a lifeline when conventional medical treatments are no longer effective. The technology provides a mechanical replacement for the heart’s function for individuals facing end-stage cardiac disease. Implantation is a complex procedure reserved for critically ill patients who require immediate circulatory support.
Defining the Technology
An artificial heart is a sophisticated mechanical pump designed to replace or augment the failing action of the heart’s ventricles. The two lower chambers, the ventricles, are responsible for the main pumping action that pushes blood to the lungs and the rest of the body. When a patient experiences end-stage heart failure, these ventricles can no longer effectively circulate blood. The artificial heart connects directly into the patient’s circulatory system, taking over this work and ensuring that blood continues to flow to maintain organ function.
Total Artificial Hearts Versus Assist Devices
The term “artificial heart” broadly covers two distinct types of devices: the Total Artificial Heart (TAH) and the Ventricular Assist Device (VAD). A Total Artificial Heart, such as the SynCardia TAH, completely replaces the native heart. The two lower chambers (the left and right ventricles) are surgically removed, and the device takes on the full responsibility for pumping blood throughout the body.
In contrast, a Ventricular Assist Device is a mechanical pump that supports one or both of the patient’s existing ventricles without removing the native heart. A Left Ventricular Assist Device (LVAD), the most common type, is surgically attached to the left ventricle and the aorta to help the weakened chamber pump oxygenated blood. VADs are far more frequently used than TAHs.
Patient Eligibility and Indications
Patients considered for an artificial heart device have irreversible, end-stage heart failure and have exhausted all other treatment options. The medical team assesses the patient’s overall health, including the function of other organs, to determine if they can withstand the complex surgery and subsequent recovery. The decision to implant a device is based on two primary clinical indications: “Bridge to Transplant” and “Destination Therapy.”
“Bridge to Transplant” refers to the temporary use of the device to keep the patient alive while they wait for a suitable donor heart to become available. The device is intended to be removed once the transplant is performed. “Destination Therapy” is the long-term, often permanent, use of the device for patients who are not eligible for a heart transplant due to factors like age or other underlying health conditions. For these individuals, the device extends life and improves their quality of life.
How Artificial Hearts Operate
Artificial hearts and assist devices move blood, employing either a pulsatile or continuous flow mechanism. Older TAH models often use a pneumatic system to create a pulsatile flow that mimics the natural beat of the heart. Many modern VADs, however, utilize a rapidly spinning rotor to generate a continuous flow of blood, which is smaller, more durable, and generally preferred.
All artificial hearts require a continuous external power source to operate the internal pump. Power is supplied through a cable, known as a driveline, which passes through the skin and connects to an external driver. The driver is a portable computer that controls the device’s function and is powered by rechargeable battery packs that patients must carry with them. These external components allow the patient a degree of mobility while ensuring the mechanical heart keeps pumping.