A Ventricular Assist Device (VAD) is a mechanical pump surgically implanted to support the function of a failing heart. It takes over the work of one or both of the heart’s lower chambers, the ventricles, when they are too weak to circulate enough blood. The VAD does not replace the heart but acts as a bridge or long-term support system. This device helps restore adequate blood flow to the body and its vital organs, significantly improving treatment options for people with advanced heart failure.
The Core Function and Mechanism
The VAD system operates by diverting blood away from the compromised heart chamber, mechanically propelling it forward, and returning it to the body’s main circulation pathway. The primary components include an internal pump, a set of tubes called cannulas, and an external control system. The pump is a small, implantable device that performs the circulatory function of the failing ventricle.
An inflow cannula is positioned within the tip of the failing ventricle to draw blood into the mechanical pump. For the most common type, which assists the left ventricle, this cannula captures oxygen-rich blood that the heart muscle cannot effectively eject. The blood enters the pump, where a rapidly spinning element accelerates the blood flow.
After the blood is pressurized within the pump, an outflow cannula channels the blood into a major artery, typically the aorta. This process bypasses the damaged heart muscle, ensuring the body receives the necessary oxygenated blood flow to sustain organ function. The entire internal device is connected to an external system by a slender cable, known as the driveline, which passes through a small exit site in the skin, usually in the abdomen.
The external components consist of a controller and battery packs, which the patient must carry. The controller acts as a small computer, constantly monitoring the pump’s function, managing its speed, and providing warnings if any issues arise. The battery pack provides the electrical power required to operate the pump, with typical full charges lasting eight to twelve hours.
Conditions That Require a VAD
VADs are reserved for patients diagnosed with advanced or end-stage heart failure. This occurs when the heart muscle is too weak to meet the body’s metabolic demands despite optimal medical therapy. The devices are considered for individuals whose quality of life is severely limited and who face a poor prognosis without mechanical support. The decision to implant a VAD is guided by the patient’s overall health, eligibility for a heart transplant, and the specific therapeutic goal.
Three main strategies define the use of VADs in treating heart failure.
Bridge to Transplant (BTT)
This strategy is for patients eligible for a heart transplant. They use the VAD to maintain health and organ function while waiting for a suitable donor heart. The VAD provides stability and can significantly improve survival during this often long waiting period.
Destination Therapy (DT)
DT is for patients with end-stage heart failure who are not candidates for a heart transplant due to other medical conditions or advanced age. The VAD is intended as a permanent solution, offering long-term support to improve survival and quality of life.
Bridge to Recovery (BTR)
BTR is less common and involves using the VAD temporarily. This gives the heart a chance to rest and potentially recover enough function to allow for the device’s eventual removal.
The Different Types of VADs
VADs are classified based on which of the heart’s two lower chambers they support. The most frequently implanted device is the Left Ventricular Assist Device (LVAD), which aids the left ventricle in pumping oxygenated blood to the aorta. Since the left ventricle performs the majority of the heart’s work, it is the chamber most often in need of mechanical support.
A Right Ventricular Assist Device (RVAD) supports the right ventricle by pumping deoxygenated blood to the lungs for oxygenation. When both ventricles are failing, a Biventricular Assist Device (BiVAD) is required. This involves implanting two separate pumps to assist both the left and right sides of the heart simultaneously.
The operational style of VADs further divides them into two categories: pulsatile flow and continuous flow devices. Older, first-generation VADs were pulsatile flow devices that mimicked the heart’s natural, rhythmic pumping action. These devices were generally larger and had more moving parts, contributing to lower reliability and durability.
Modern devices are predominantly continuous flow VADs, which move blood in a non-stop stream rather than an intermittent pulse. These second- and third-generation devices are considerably smaller, more durable, and more reliable than pulsatile predecessors. A unique characteristic of continuous flow VADs is that the patient may not have a palpable pulse or measurable blood pressure using conventional methods, even though their body receives the necessary blood flow.
Daily Life and Management of a VAD
Living with a VAD requires a significant adjustment to a “new normal,” as the patient is constantly connected to the external controller and batteries. Patients must always carry the equipment, wearing the controller and battery packs, often in a shoulder strap or belt. Planning ahead is necessary to ensure a continuous power supply, and two charged batteries must be carried.
A major aspect of VAD management involves meticulous care of the driveline exit site, where the cable passes through the skin. This site is a potential entry point for bacteria, making infection a common and serious risk. Patients and their caregivers are taught how to perform sterile dressing changes. This routine keeps the site clean, dry, and minimizes driveline movement.
Patients must strictly adhere to a medication regimen, including heart failure medications and blood thinners. Blood thinners are critical to prevent clots from forming within the mechanical pump. The presence of foreign material increases the risk of clot formation, which can lead to a stroke or device malfunction. Other risks include bleeding, a complication of being on blood thinners.
While the device allows for a return to many normal activities, restrictions are in place to protect the equipment and the patient. Activities that involve submerging the device in water, such as swimming or using a hot tub, are prohibited to prevent damage and infection. Contact sports and heavy lifting are also restricted to ensure the device and the surgical site remain protected.