Mechanical circulatory support devices treat severe heart conditions, especially heart failure. These technologies assist the heart in pumping blood, maintaining circulation and supporting organ function when the heart cannot do so effectively. Left Ventricular Assist Devices (LVADs) and Impella devices are two distinct approaches to cardiac assistance. This article explores their unique features and applications.
What are Left Ventricular Assist Devices
A Left Ventricular Assist Device (LVAD) is a mechanical pump that supports the left ventricle, the heart’s main pumping chamber. This device helps circulate oxygen-rich blood from the left ventricle to the aorta and throughout the body. LVADs are implanted surgically, providing long-term support for patients with advanced heart failure.
The indications for LVAD implantation include “bridge to transplant” therapy, supporting patients while awaiting a heart transplant. LVADs can also be used as “destination therapy,” offering a long-term solution for patients not candidates for heart transplantation. In some cases, they serve as a “bridge to recovery” if heart function is expected to improve, or a “bridge to candidacy” to assess suitability for a transplant.
An LVAD system consists of several components. The pump, often located at the apex of the left ventricle, contains an impeller that rotates at high speeds, generating substantial blood flow, potentially up to 10 liters per minute. An inflow cannula draws blood from the left ventricle into the pump, and an outflow graft carries the blood from the pump to the ascending aorta, bypassing the failing ventricle.
The device also includes a driveline, a cable that extends from the internal pump and exits the body, usually in the patient’s abdomen. This driveline connects to an external controller that regulates pump speed, monitors performance, and displays alarms. Power is supplied by rechargeable lithium-ion batteries, with patients typically carrying at least two at all times, offering up to 14 hours of power depending on the device.
What are Impella Devices
Impella devices are temporary, catheter-based mechanical circulatory support designed to directly pump blood. Unlike surgically implanted LVADs, Impella devices are inserted percutaneously, often through the femoral artery, and advanced into the left ventricle across the aortic valve. This positioning allows the device to draw blood from the left ventricle and expel it into the ascending aorta.
The primary function of an Impella device is to unload the left ventricle, reducing its workload and myocardial oxygen demand, while simultaneously increasing systemic cardiac output. Impella devices can provide blood flow rates ranging from 2.5 to 5.0 liters per minute, depending on the model. This immediate and sustained ventricular unloading can improve hemodynamic stability.
Impella devices are indicated for acute cardiac support in specific scenarios. These include high-risk percutaneous coronary interventions (PCI), where the device helps maintain blood flow and prevent hemodynamic instability during complex procedures, especially in patients with severe coronary artery disease. They are also used for patients experiencing cardiogenic shock, a severe condition where the heart cannot pump enough blood to meet the body’s needs, often complicating acute myocardial infarction.
Impella devices can also be employed in cases of post-cardiotomy shock, which occurs after heart surgery, or in acute decompensated heart failure due to conditions like cardiomyopathy or myocarditis. The temporary nature of Impella support, generally for a few days up to 14 days, makes it suitable for short-term stabilization or as a bridge to other therapies like durable LVAD implantation or heart recovery.
Distinguishing Between LVAD and Impella
The differences between Left Ventricular Assist Devices (LVADs) and Impella devices are based on their duration of use, method of placement, and the specific cardiac conditions they address. These distinctions determine when each device is chosen to support a patient’s heart function.
LVADs are designed for long-term support, serving as either a “bridge to transplant” for patients awaiting a heart donor or as “destination therapy” for those ineligible for a transplant. Impella devices, conversely, are temporary solutions, typically providing support for a few days, with some models approved for up to 14 days. They are used to stabilize patients during acute cardiac events or as a short-term bridge to recovery or more definitive therapies.
The placement of these devices also differs in invasiveness. An LVAD requires open-heart surgery for implantation, with the pump positioned inside the chest and a driveline exiting the body to connect to external components. Impella devices are inserted percutaneously, advanced through a catheter, often from the femoral artery in the leg, and positioned within the heart without major surgery. This less invasive insertion is an advantage for patients needing rapid, acute support.
Their primary purposes align with their duration and placement. LVADs are employed for chronic heart failure, where the heart’s pumping ability is severely impaired over an extended period, requiring continuous assistance. Impella devices, on the other hand, provide acute cardiac support for sudden, severe heart dysfunction, such as cardiogenic shock following a heart attack or during high-risk coronary interventions, where immediate and temporary hemodynamic stabilization is necessary.
The mechanisms by which they assist the heart also show distinct approaches. LVADs function as continuous-flow pumps, drawing blood from the left ventricle and propelling it into the aorta, essentially bypassing the weakened ventricle. Impella devices operate as microaxial flow pumps, directly pumping blood from the left ventricle into the aorta by drawing blood from an inlet in the ventricle and expelling it through an outlet in the aortic root. This direct pumping action provides left ventricular unloading and increased cardiac output.
Life with a Cardiac Support Device
Living with a cardiac support device involves adjustments and ongoing care, with the experience differing based on whether the device is an LVAD or an Impella. For LVAD patients, daily life centers on managing external components and adhering to specific care routines. This includes regular battery changes for the external power supply, which patients typically carry in a bag or vest, ensuring continuous operation of the implanted pump.
Driveline care is a routine aspect of LVAD management. The driveline, which exits the body, requires frequent dressing changes to prevent infection at the exit site. Patients and caregivers receive training on how to perform these changes and recognize potential problems.
Lifestyle adjustments are common for LVAD patients, including modifications to sleeping positions to avoid pressure on the driveline and restrictions on activities like swimming or bathing due to the external electrical components. Most patients are able to resume many daily activities, and physical activity, guided by a medical team, is encouraged to regain strength. Ongoing medical follow-up is regular, with frequent clinic visits in the initial months for equipment checks, driveline inspections, and blood work, becoming less frequent over time.
For patients receiving an Impella device, the experience is temporary and occurs within an intensive care setting. Since Impella devices are used for acute support, patients remain hospitalized under close medical supervision. Monitoring of the device’s function and the patient’s hemodynamic status is continuous. While Impella provides temporary relief and can lead to heart recovery, the focus is on stabilization and either transitioning to a more permanent solution like an LVAD or allowing the heart to recover sufficiently for device removal.