A BIVAD (Biventricular Assist Device) is a mechanical circulatory support system that provides support to both the left ventricle and the right ventricle of the heart. It is used in patients with severe biventricular heart failure who are awaiting a heart transplant. The BIVAD is typically used as a bridge to heart transplant for patients who require temporary support to maintain vital organ perfusion while awaiting a suitable donor heart.

Unlike devices that only support one side of the heart, a BIVAD provides support for both ventricles, assisting in pumping blood to the lungs and the rest of the body. This device is particularly important for patients who have end-stage heart failure involving both ventricles, often after conditions like dilated cardiomyopathy, ischemic heart disease, or severe cardiogenic shock.

What is a BIVAD?

A Biventricular Assist Device (BIVAD) is a type of mechanical circulatory support device that helps pump blood from both the left and right sides of the heart. It consists of two pumps (one for each ventricle) that work in tandem to ensure adequate blood flow and oxygenation of vital organs. BIVADs are commonly used in patients who are too ill to undergo heart transplantation without mechanical support.

BIVADs consist of the following components:

1. Left Ventricular Assist Device (LVAD): Supports the left ventricle, which pumps oxygenated blood to the rest of the body.
2. Right Ventricular Assist Device (RVAD): Supports the right ventricle, which pumps deoxygenated blood to the lungs for oxygenation.

These devices are connected to the heart through tubes that are inserted into the ventricles and often require external components such as a controller and batteries to power the pumps.

How a BIVAD Works

1. Left Ventricular Assist Device (LVAD):
• The LVAD helps pump blood from the left ventricle to the aorta, which delivers oxygenated blood throughout the body. It helps improve systemic circulation and reduces the workload on the left ventricle.
2. Right Ventricular Assist Device (RVAD):
• The RVAD pumps blood from the right ventricle to the pulmonary artery, sending deoxygenated blood to the lungs for oxygenation. It improves pulmonary circulation and helps stabilize oxygen levels in the blood.

By supporting both ventricles, the BIVAD helps maintain vital organ perfusion in critically ill patients, preventing multi-organ failure, and provides a bridge to heart transplant.

Indications for BIVAD as a Bridge to Heart Transplant

A BIVAD is typically used in patients with biventricular heart failure or severe cardiogenic shock who are awaiting a heart transplant. Common indications include:

1. Biventricular Heart Failure:
• Patients with dilated cardiomyopathy or ischemic cardiomyopathy may develop heart failure involving both the left and right ventricles. A BIVAD can provide temporary support to both sides of the heart while awaiting a heart transplant.
2. Cardiogenic Shock:
• In cases of cardiogenic shock, where the heart cannot effectively pump blood to the body, a BIVAD can provide life-saving support by stabilizing circulation until a donor heart is available.
3. Severe Right and Left Ventricular Dysfunction:
• Patients with severe left ventricular dysfunction and right ventricular dysfunction (often from conditions like pulmonary hypertension, acute myocardial infarction, or severe heart failure) may require the dual support that a BIVAD offers.
4. Post-Surgical Heart Failure:
• After complex cardiac surgeries, such as coronary artery bypass grafting (CABG) or valve replacement surgery, some patients may experience right and left ventricular failure that necessitates mechanical support.
5. Post-Myocardial Infarction (Heart Attack):
• In patients who have had massive myocardial infarctions leading to severe dysfunction of both ventricles, a BIVAD can provide circulatory support while waiting for a heart transplant.

How BIVAD Works as a Bridge to Heart Transplant

A BIVAD serves as a temporary circulatory support system, helping to maintain blood flow to both the lungs and the body while the patient awaits a heart transplant. Here's how it works:

1. Restoring Cardiac Output:
• The LVAD provides support to the left ventricle, increasing cardiac output and helping to pump oxygenated blood throughout the body. The RVAD provides support to the right ventricle, ensuring that blood is sent to the lungs for oxygenation.
2. Improving Organ Perfusion:
• By providing adequate circulatory support, the BIVAD improves perfusion to vital organs like the brain, kidneys, and liver, preventing organ failure and improving the patient’s overall condition.
3. Stabilizing Hemodynamics:
• The BIVAD helps stabilize the hemodynamic status of patients in cardiogenic shock, improving blood pressure and organ function, thus providing time for a heart transplant.
4. Bridge to Transplant:
• While the BIVAD provides circulatory support, it also allows the patient to be stable enough to wait for a donor heart. This device can be crucial in improving survival rates while waiting for a suitable heart to become available.

Procedure for BIVAD Insertion

The procedure for implanting a BIVAD is performed by a cardiothoracic surgeon and is generally done under general anesthesia. The process typically follows these steps:

1. Incision:
• The patient undergoes a sternotomy (surgical opening of the chest) or another access route to reach the heart.
2. Insertion of the LVAD:
• The LVAD catheter is inserted into the left ventricle and attached to the ascending aorta to pump blood to the systemic circulation.
3. Insertion of the RVAD:
• The RVAD catheter is inserted into the right ventricle and connected to the pulmonary artery to pump blood to the lungs.
4. Attachment of Tubes and Controllers:
• Tubes from the devices are connected to external components, including pumps, controllers, and power supplies (batteries or external connections).
5. Postoperative Care:
• After implantation, the patient is carefully monitored in an intensive care unit (ICU) to ensure the devices are functioning properly and to prevent complications like infection, thrombosis, or device malfunction.

Benefits of BIVAD as a Bridge to Heart Transplant

1. Life-Saving Circulatory Support:
• The BIVAD provides vital circulatory support to both the left and right ventricles, improving overall blood flow to vital organs and stabilizing the patient until a transplant can be performed.
2. Improved Organ Perfusion:
• By enhancing blood flow, the BIVAD ensures adequate perfusion to the brain, kidneys, liver, and other organs, preventing organ failure due to poor circulation.
3. Reduced Cardiac Workload:
• By taking over the pumping function of the left and right ventricles, the BIVAD reduces the heart’s workload, allowing it to rest and function more efficiently, even when severely compromised.
4. Bridge to Recovery or Heart Transplant:
• In some cases, patients may experience partial recovery of heart function while on BIVAD support, allowing them to avoid a transplant. However, in most cases, it serves as a bridge to heart transplantation, improving survival rates and overall outcomes.
5. Minimally Invasive:
• Although implantation requires a surgical procedure, the BIVAD is still considered a minimally invasive solution compared to a heart transplant, providing a less risky, temporary support option.

Risks and Complications of BIVAD Use

While BIVAD provides life-saving support, it carries certain risks and potential complications, including:

1. Infection:
• The implantation of any mechanical device increases the risk of infection, especially at the surgical site or related to the device components (e.g., pumps, tubes).
2. Thrombosis and Clots:
• Blood clots can form within the device or on the heart valves, leading to thrombosis (blockage of blood flow) and embolism (clot traveling to other parts of the body). This can cause stroke or pulmonary embolism.
3. Hemolysis:
• Mechanical support devices like BIVAD can sometimes damage red blood cells, leading to hemolysis (destruction of red blood cells) and subsequent anemia.
4. Vascular Complications:
• The insertion of the cannulas into the heart or major blood vessels can cause vascular injury, leading to complications like bleeding, hematoma, or arterial rupture.
5. Device Malfunction:
• Although rare, the BIVAD can malfunction or become dislodged, requiring immediate intervention to replace or reposition the device.
6. Kidney Injury:
• Acute kidney injury can occur due to low blood pressure, poor perfusion, or complications from the device, especially in patients with preexisting kidney issues.
7. Bleeding:
• Patients on anticoagulation therapy to prevent clot formation may be at higher risk for bleeding complications, including gastrointestinal bleeding or hemorrhagic stroke.

Post-BIVAD and Heart Transplant Surgery

Once a donor heart becomes available, the patient will undergo heart transplant surgery. During the transplant, the BIVAD will be removed. After the transplant, the patient will be closely monitored for rejection, infection, and other complications. The patient will begin immunosuppressive therapy to prevent rejection of the new heart.

Conclusion

The BIVAD (Biventricular Assist Device) is a crucial tool for providing temporary circulatory support in patients with severe biventricular heart failure or cardiogenic shock awaiting a heart transplant. By supporting both the left and right ventricles, the BIVAD improves organ perfusion, reduces cardiac workload, and provides a bridge to heart transplant, improving patient survival and overall outcomes. While it carries risks, it is a vital intervention for many critically ill patients awaiting heart transplantation.