A mechanical heart is an electromechanical device engineered to either assist or completely replace the pumping function of a severely diseased heart. This technology is a form of durable mechanical circulatory support, designed to maintain adequate blood flow throughout the body when the natural organ has failed. By taking over the work of the heart’s lower chambers, these devices ensure that oxygenated blood continues to circulate, supplying the body’s tissues and organs.
Why Mechanical Hearts Are Necessary
Mechanical hearts are typically indicated for individuals suffering from end-stage heart failure, a condition where the heart muscle is too weak to pump enough blood to meet the body’s needs. When standard medications and procedures can no longer manage the decline in cardiac function, mechanical support becomes a necessary intervention. These devices serve two primary roles.
One role is “Bridge to Transplant” (BTT), where the device supports the patient until a suitable donor heart becomes available for transplantation. The second role is “Destination Therapy” (DT), which offers a permanent, long-term treatment option for patients who are not eligible for a heart transplant due to other medical conditions or advanced age.
The Two Primary Device Categories
The field of mechanical circulatory support is defined by two categories of devices. The most common category is the Ventricular Assist Device (VAD), which is designed to support the patient’s existing heart rather than replace it. A VAD is a pump implanted alongside the native heart, drawing blood from a failing chamber and propelling it into the body’s main circulation.
The majority of these devices are Left Ventricular Assist Devices (LVADs) because the left ventricle pumps blood to the entire body. If the right ventricle also fails, a BiVAD configuration may be employed to support both ventricles simultaneously. In contrast, the Total Artificial Heart (TAH) provides a complete replacement of the heart’s two lower chambers, the ventricles. TAHs require the surgical removal of the native ventricles and are attached directly to the patient’s upper chambers (atria) and major arteries.
How the Technology Functions
Modern mechanical hearts operate using engineering principles, moving away from older designs that tried to mimic the natural heart’s rhythmic pulse. Current-generation devices are predominantly continuous-flow pumps, which utilize a high-speed rotor or impeller to generate a steady, non-pulsatile stream of blood. This constant spinning action generates a continuous flow that is efficient and durable.
The system requires several components. The pump unit itself is implanted within the chest cavity. This internal pump is connected to an external system via a percutaneous driveline, a cable that passes through the skin near the abdomen. Outside the body, the driveline connects to a controller, which manages the pump’s speed and monitors its function. The entire system is powered by external battery packs, which must be worn by the patient to ensure uninterrupted operation.
The continuous flow generated by these pumps means that a patient with a modern VAD may not have a palpable pulse. This steady flow is sufficient to maintain organ perfusion and blood pressure throughout the body, despite the lack of a traditional, rhythmic beat.
Living with a Device
Implanting a mechanical heart is a major surgical procedure, typically requiring open-heart surgery to place the pump and connect it to the heart and major blood vessels. Following the procedure, life with the device requires a strict regimen of management and lifestyle adjustments. The patient must constantly manage the external components, including the controller and the battery packs, which need regular recharging to ensure the pump never loses power.
A primary concern for all mechanical heart recipients is the risk of blood clotting, as blood components can react to the non-biological surfaces of the pump and internal components. To counteract this, patients must adhere to lifelong anti-coagulation therapy, taking blood-thinning medications daily to prevent the formation of dangerous clots. This regimen requires regular blood tests to ensure the medication dosage is kept within a narrow therapeutic range.
Another risk is infection at the driveline exit site, where the cable passes through the skin. This area must be kept clean and dry to prevent bacteria from entering the body and traveling to the implanted device. Managing these risks allows individuals with mechanical hearts to regain physical function and often return to many normal daily activities.