What is a mechanical assist device?
A mechanical assist device is a man-made pump that can temporarily help the pumping action of the heart.
Why is it used?
A mechanical assist device is used to help maintain blood circulation. There are several different types of mechanical assist devices. They include:
Intra-aortic Balloon Pump (IABP), also known as Intra-aortic balloon counterpulsation (IABC) or balloon pump, is a balloon that inflates and deflates at a specified rate to help the flow of blood through the aorta and decrease the workload on the left ventricle (the main pumping chamber of the heart). Typically, this device is used to help the left side of the heart for relatively short periods of time. Because it is usually used for less than 10 days, it is referred to as “acute support.” Patients who require this type of temporary support include those with:
- a recent heart attack.
- a heart inflammation (acute myocarditis).
- difficulty coming off cardiopulmonary bypass after open-heart surgery.
Implantable Ventricular Assist Device (VAD), also referred to as a ventricular assist system or VAS, is a mechanical pump that helps a weakened heart pump blood throughout the body. VADs are sometimes referred to as “artificial hearts” but in reality they do not replace the heart. Instead, a VAD supplements and helps the patient’s own heart to pump blood by taking over the function of either or both ventricles (lower chambers) of your heart when needed. A VAD is typically used when the heart is severely weakened, such as in severe or end-stage heart failure. These patients may require longer-term support. In these cases, a VAD may be used:
- until a donor heart for heart transplantation becomes available (bridge to transplant).
- until the heart function recovers (bridge to recovery).
- as long-term therapy in patients with end-stage heart failure who are not candidates for transplant.
Total Artificial Heart (TAH) Much research has been conducted trying to develop a mechanical device that can permanently replace the heart and has no external tubes or cables. Several successful cases have been reported. However, research is continuing.
What is done?
Intra-aortic Balloon Pump (IABP)
Surgery is not required to put in an intra-aortic balloon pump. In most cases, a thin, flexible tube called a catheter is inserted into a blood vessel in the leg and threaded into the aorta of the heart. The aorta is the main artery that carries oxygen-rich blood to the rest of the body.
Through the catheter, a small balloon (the IABP balloon) is positioned in the aorta. The IABP balloon is connected to a computer console that:
- controls the inflation and deflation of the IABP balloon.
- provides an emergency backup power supply.
- monitors the electrical signal of the heart muscle through an electrocardiogram (ECG or EKG).
- monitors the pressure within the aorta.
When the heart muscle relaxes, the balloon inflates. This increases blood flow to the coronary arteries. Just before the heart muscle contracts (pumps), the balloon deflates, creating a vacuum effect that helps blood flow from the heart. The process of inflating and deflating the balloon as the heart muscle relaxes and contracts is referred to as counterpulsation.
An IABP is usually implanted for a short period of time. When the treatment is no longer needed, the balloon and the catheter are withdrawn.
Ventricular Assist Device (VAD)
Implantation of the VAD requires open-heart surgery. There are two forms of VAD – a Left Ventricular Assist Device (LVAD) and a Right Ventricular Assist Device (RVAD), which are both implanted in the chest or abdomen. There are also devices that can assist both ventricules or bi-ventricular devices (biVAD):
- LVAD - an inflow tube (conduit) is attached to the bottom of the left ventricle and an outflow tube is attached to the aorta (the large artery that carries blood away from the heart).
- RVAD – an inflow tube is attached to the right ventricle and the outflow tube is attached to the pulmonary artery (the artery that carries blood from the heart to the lungs).
- Power leads pass from the internal device through the skin and attach to an external control and power base unit or battery pack outside of the body. The controller and batteries can be worn in a belted waist pack, a holster under the arm, or be connected to a power base unit and plugged into a wall outlet.
What can you expect?
Intra-aortic Balloon Pump
- Implantation of an IABP is a non-surgical procedure.
- It is usually performed in an operating room, catheterization laboratory or intensive care unit.
- To prepare, the area where the catheter will be inserted is shaved and sterilized.
- The catheter is usually inserted through the femoral artery in the groin, but may be inserted in the arm (brachial artery).
- An intravenous (IV) line is inserted.
- A mild sedative may be given to calm the patient and a local anesthetic injected at the insertion site.
- Once the site is numbed, an IABP-tipped catheter is inserted.
- Using a special form of moving X-ray machine called a fluoroscope, the surgeon threads the catheter through the body and up into the heart. Once positioned in the aorta, the catheter remains in place until the IABP is removed.
Ventricular Assist Device
Implantation of a VAD involves open-heart surgery. Some VADs cannot be used in very short or thin patients, or in people with serious renal (kidney), liver or lung disease, blood clotting disorders, or infections that do not respond to antibiotics. A VAD can allow patients who have been hospitalized to return home to wait for a donor heart.
- If the VAD implantation is a scheduled procedure, you will probably be given an appointment at the hospital a week or so prior to the surgery date so several tests can be performed.
- Most patients are admitted the night before their surgery.
- You must not eat or drink anything for at least eight hours prior to surgery.
- Immediately before surgery, you will be given a sedative to help you relax.
- The chest area will be shaved and disinfected, and an intravenous (IV) line will be inserted.
- In the operating room, a general anesthetic is given so you will be asleep throughout the entire operation.
- After you are completely anesthetized, three tubes will be inserted:
- a tube down your windpipe, which will be connected to a machine called a respirator to take over your breathing during the surgery.
- a tube into your stomach to stop liquid and air from collecting in your stomach so you will not feel sick and bloated when you wake up.
- a tube into your bladder to collect any urine produced during the operation.
- The heart must be stopped so the surgeons can work on it.
- To ensure your body continues to receive a flow of oxygen-rich blood, you will be hooked up to a heart-lung machine. This machine takes over the pumping action of the heart.
The surgery can take several hours.
- When you awaken, you will be in the recovery room or an intensive care unit (ICU).
- You can expect to stay in the hospital at least five days.
- How quickly you recover from surgery will depend in large part upon how healthy you were before the surgery.
- During this time, tests will be conducted to assess and monitor your condition.
- You and your family will also be taught what to do when you return home with your VAD.
- Most intermediate and long-term VADs allow people to go back to a more natural lifestyle.
Total Artificial Heart (TAH)
Like the VAD, implantation of a TAH involves open heart surgery. TAHs are still experimental and are only available in a few research centres.