Ventricular assist devices (VADs) are mechanical pumps that are used to support the function of a failing heart. They are designed to assist or replace the function of one or both ventricles, the main pumping chambers of the heart. VADs have become an important treatment option for patients with end-stage heart failure who are not eligible for heart transplantation or who are awaiting a suitable donor organ. In this blog post, we will discuss the different types of VADs, indications for their use, patient selection and preoperative evaluation, surgical techniques for implantation, postoperative management, complications, weaning from VADs, destination therapy, and future directions in VAD development.
Types of Ventricular Assist Devices
There are two main types of VADs: left ventricular assist devices (LVADs) and right ventricular assist devices (RVADs). LVADs are used to support the function of the left ventricle, which is responsible for pumping oxygenated blood to the rest of the body. RVADs, on the other hand, support the function of the right ventricle, which pumps deoxygenated blood to the lungs for oxygenation.
Left Ventricular Assist Devices (LVADs)
LVADs can be further classified into two types: pulsatile and continuous flow. Pulsatile LVADs mimic the natural pulsatile function of the heart by delivering blood in a pulsatile manner. These devices have been in use since the 1980s and were the first type of VADs to be implanted in humans. However, they have largely been replaced by continuous flow LVADs due to their smaller size, longer durability, and lower complication rates.
Continuous flow LVADs, as the name suggests, deliver blood in a continuous flow rather than in a pulsatile manner. These devices are smaller and have a simpler design compared to pulsatile LVADs, making them easier to implant and maintain. They also have a longer lifespan, with some devices lasting up to 10 years.
Right Ventricular Assist Devices (RVADs)
RVADs are used to support the function of the right ventricle, which is responsible for pumping blood to the lungs for oxygenation. These devices are less commonly used compared to LVADs, as right-sided heart failure is less common than left-sided heart failure. However, in cases where both ventricles are failing, a combination of LVAD and RVAD may be used, known as a biventricular assist device (BiVAD).
Indications for Ventricular Assist Device Implantation
The main indication for VAD implantation is end-stage heart failure, which is defined as severe heart failure that is refractory to medical therapy. This means that despite optimal medical treatment, the patient’s symptoms and quality of life continue to deteriorate. Other indications for VAD implantation include:
- Bridge to transplant: VADs can be used as a temporary measure to support patients while they await a suitable donor heart for transplantation.
- Destination therapy: In some cases, VADs may be used as a long-term treatment option for patients who are not eligible for heart transplantation due to age or other medical conditions.
- Bridge to recovery: In rare cases, VADs may be used to support the heart while it recovers from an acute event, such as a heart attack or viral infection.
- Bridge to decision: VADs may be used as a temporary measure to support patients while their eligibility for heart transplantation is being evaluated.
Patient Selection and Preoperative Evaluation for Ventricular Assist Devices
Patient selection for VAD implantation is crucial to ensure optimal outcomes. The decision to implant a VAD is made by a multidisciplinary team, including cardiologists, cardiac surgeons, and VAD coordinators. The following factors are taken into consideration when selecting patients for VAD implantation:
- Severity of heart failure: Patients with end-stage heart failure who are not responding to medical therapy are the most suitable candidates for VAD implantation.
- Age: While there is no age limit for VAD implantation, older patients may have a higher risk of complications and may not be eligible for heart transplantation.
- Comorbidities: Patients with other medical conditions, such as kidney disease or lung disease, may not be suitable for VAD implantation.
- Psychosocial factors: Patients must have a good support system in place and be able to adhere to postoperative care instructions.
- Surgical risk: Patients must be able to tolerate major surgery and have a low risk of perioperative complications.
Before VAD implantation, patients undergo a thorough preoperative evaluation to assess their overall health and suitability for the procedure. This includes:
- Physical examination: A complete physical examination is performed to assess the patient’s general health and identify any potential contraindications for VAD implantation.
- Laboratory tests: Blood tests are done to assess kidney and liver function, as well as to check for any infections or bleeding disorders.
- Imaging studies: Echocardiography, cardiac MRI, and/or cardiac catheterization may be performed to evaluate the structure and function of the heart and determine the need for VAD implantation.
- Psychological evaluation: Patients undergo a psychological evaluation to assess their mental health and ability to cope with the challenges of living with a VAD.
- Education: Patients and their families receive education about the VAD implantation procedure, postoperative care, and potential complications.
Surgical Techniques for Ventricular Assist Device Implantation
VAD implantation is a major surgical procedure that requires a skilled cardiac surgeon and a specialized team. The procedure is performed under general anesthesia and involves making an incision in the chest to access the heart. The specific surgical technique used depends on the type of VAD being implanted.
Left Ventricular Assist Device (LVAD) Implantation
The most common surgical technique for LVAD implantation is the median sternotomy approach, where an incision is made along the sternum (breastbone). This provides direct access to the heart and allows the surgeon to implant the VAD. The following steps are involved in LVAD implantation:
- Preparing the Heart: The surgeon prepares the heart by placing temporary pacing wires and a venting catheter to drain blood from the left ventricle.
- Placing the Inflow Cannula: The inflow cannula, which is connected to the VAD pump, is inserted into the left ventricle through an incision made in the apex (bottom) of the heart.
- Placing the Outflow Graft: The outflow graft, which carries blood from the VAD pump to the aorta, is sewn onto the ascending aorta.
- Connecting the Pump: The VAD pump is then connected to the inflow cannula and outflow graft.
- Closing the Incision: The incision in the heart is closed, and the chest is closed with sutures or staples.
Right Ventricular Assist Device (RVAD) Implantation
RVAD implantation is less commonly performed compared to LVAD implantation. The surgical technique used is similar to that of LVAD implantation, except that the inflow cannula is inserted into the right ventricle instead of the left ventricle. In some cases, both LVAD and RVAD may be implanted simultaneously, known as a biventricular assist device (BiVAD).
Postoperative Management of Patients with Ventricular Assist Devices
After VAD implantation, patients are closely monitored in the intensive care unit (ICU) for the first few days. The following aspects of postoperative management are crucial to ensure optimal outcomes:
Hemodynamic Monitoring
Patients with VADs require continuous hemodynamic monitoring to assess the function of the device and detect any complications. This includes monitoring blood pressure, heart rate, and oxygen saturation.
Anticoagulation Therapy
VADs are associated with a high risk of blood clots, which can lead to serious complications such as stroke or device malfunction. Therefore, patients are started on anticoagulation therapy immediately after surgery to prevent blood clots from forming. The type and dose of anticoagulant used may vary depending on the type of VAD implanted.
Wound Care
Proper wound care is essential to prevent infections and promote healing. The surgical incision must be kept clean and dry, and any signs of infection, such as redness, swelling, or drainage, should be reported to the healthcare team immediately.
Medications
In addition to anticoagulants, patients with VADs may also require other medications, such as antibiotics, diuretics, and immunosuppressants. These medications are prescribed based on the patient’s individual needs and may be adjusted over time.
Rehabilitation
After VAD implantation, patients undergo a rehabilitation program to help them regain their strength and independence. This may include physical therapy, occupational therapy, and dietary counseling.
Complications of Ventricular Assist Devices
While VADs have significantly improved the survival and quality of life of patients with end-stage heart failure, they are associated with a number of potential complications. These include:
- Infection: VADs are foreign objects that are implanted into the body, making them susceptible to infection. Infections can occur at the site of the surgical incision or within the device itself.
- Bleeding: Anticoagulation therapy increases the risk of bleeding, which can be life-threatening in some cases. Patients with VADs must be monitored closely for signs of bleeding and receive prompt treatment if necessary.
- Thrombosis: Blood clots can form within the VAD, leading to device malfunction or stroke.
- Device malfunction: VADs are mechanical devices that can malfunction due to technical issues or wear and tear. This may require emergency surgery to replace or repair the device.
- Right heart failure: RVADs are associated with a higher risk of right heart failure, which can occur due to inadequate support of the right ventricle or obstruction of the outflow graft.
- Device-related complications: Other potential complications include device migration, pump thrombosis, and hemolysis (breakdown of red blood cells).
Weaning from Ventricular Assist Devices
The ultimate goal of VAD implantation is to improve the patient’s heart function to the point where the device is no longer needed. This process is known as weaning and involves gradually reducing the level of support provided by the VAD until it can be safely removed.
Weaning from a VAD requires careful monitoring and assessment of the patient’s heart function. This is done through various tests, such as echocardiography, cardiac catheterization, and exercise testing. The decision to wean a patient from a VAD is made by the multidisciplinary team and is based on the patient’s clinical status and test results.
Destination Therapy with Ventricular Assist Devices
Destination therapy refers to the use of VADs as a long-term treatment option for patients who are not eligible for heart transplantation. This may be due to age, medical comorbidities, or other factors. Destination therapy has become an important option for patients with end-stage heart failure who have exhausted all other treatment options.
The main goal of destination therapy is to improve the patient’s quality of life by providing long-term support for the failing heart. However, it is important to note that VADs are not a cure for heart failure and may be associated with complications and limitations in daily activities.
Future Directions in Ventricular Assist Device Development
Ventricular assist devices have come a long way since their first use in the 1980s. With advancements in technology and surgical techniques, VADs have become smaller, more durable, and easier to implant and manage. However, there is still room for improvement, and researchers continue to work on developing new and improved VADs. Some areas of focus include:
- Miniaturization: Researchers are working on developing smaller VADs that can be implanted through minimally invasive techniques.
- Fully implantable VADs: Currently, VADs require an external power source, which limits the patient’s mobility and increases the risk of infection. Researchers are working on developing fully implantable VADs that do not require an external power source.
- Biocompatible materials: The use of biocompatible materials in VADs can reduce the risk of blood clots and infections.
- Artificial intelligence: The use of artificial intelligence in VADs can help predict and prevent complications, leading to better outcomes for patients.
Conclusion
Ventricular assist devices have revolutionized the treatment of end-stage heart failure and have significantly improved the survival and quality of life of patients who are not eligible for heart transplantation. With ongoing research and development, VADs will continue to evolve and become even more effective and safer in the future. However, it is important to remember that VADs are not a cure for heart failure and must be carefully managed to ensure optimal outcomes. Patient selection, preoperative evaluation, surgical techniques, postoperative management, and weaning from VADs are all crucial aspects of the care of patients with VADs. With proper management and advancements in technology, VADs will continue to play a vital role in the treatment of end-stage heart failure.