At times, the muscle of the heart can be so severely weakened by the various diseases of the heart that it can no longer pump strongly enough to support life. Various intravenous medications can be given to support the heart in these circumstances but sometimes even they are not enough.
A variety of mechanical devices have been developed to assist in these situations. They are generally temporary measures and are withdrawn after the disease process has been corrected. For disease processes that cannot be corrected, the device is left in place until a transplant is performed.
One of the earliest devices developed and still in use today is the intraaortic balloon pump. This can be placed in the intensive care unit, cardiac catheterization lab, or the operating room. A local anesthetic is given over the artery at the top of the leg and the device is introduced into the artery. It is essentially a long balloon that sits in the aorta-the main artery in the body. It is hooked up to a large console that is continuously maintained by a specially trained technician. The console inflates the balloon during the time that heart is filling with blood for the next heart beat. The inflated balloon pumps the blood and then deflates when the heart is ready with the next heart beat. Thus, enough blood flow is supplied to the organs of the body and some of the workload of the heart is reduced. This allows the heart to recover its strength. Some of the drawbacks of this device are that it can only be left in for a short period of time and the patient cannot get out of bed.
The current state of the art are left ventricular assist devices. These are implanted under general anesthesia by opening the breastbone. A tube runs from the main pumping chamber of the heart (the left ventricle) to the main artery of the body (the aorta). The tube contains valves leading into and out from a pumping chamber. A second tube runs through the skin to connect the pumping chamber to an external battery pack which the patient wears with a shoulder strap. The patient can be discharged from the hospital and be able to walk around. The devices even have activity sensors to increase the pump output when needed. Backup mechanisms are available should the device fail. In patients with severe heart failure who are not candidates for heart transplant, these devices have doubled the survival rate.
Biventricular assist can be accomplished to support the other pumping chamber of the heart (the right ventricle) using a similar device connecting the right ventricle to the pulmonary artery.
These devices are most commonly implanted to support patients waiting for a suitable donor heart for a heart transplant. Sometimes, we see the patient's heart recover its own function while the device is in place, eventually allowing for discontinuation of the device and obviating the need for a heart transplant. Other patients may stay on the device chronically if they are not eligible for a heart transplant and their hearts do not improve their function.
Once again, total artificial hearts are being implanted in an experimental trial. It is hoped these newer devices will avoid the problems associated with earlier devices.
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