Wednesday August 3 2011
The artificial heart implant
A 40-year-old father has become the first UK patient to receive a portable total artificial heart implant. Before receiving the implant Matthew Green had been critically ill from end-stage heart failure and it was thought he might not survive until a suitable donor heart could be found. However, his symptoms have improved since doctors fitted him with a new artificial heart device. The device can be run using a special backpack power unit rather than the large, fixed machines that must normally be used to power implants in hospital.
Mr Green underwent a six-hour operation carried out by surgeons at Papworth Hospital, Cambridge, in which his damaged heart was replaced with a Total Artificial Heart (TAH). The implant is only a temporary device designed to keep pumping blood to vital organs until a suitable donor heart is found and, eventually, Mr Green will have to undergo a transplant. However, the device appears to be working successfully as a temporary measure as it has eliminated Mr Green’s symptoms of heart failure and allowed him to make an “excellent” recovery. He has now gone home to wait for a suitable donor to be found.
What exactly is an artificial heart?
An artificial heart is a plastic device designed to replace a patient’s heart ventricles. The ventricles are the two large, lower chambers that pump blood towards the lungs and into the arteries that supply the whole body with blood. To fit the implant the ventricles are surgically removed and plastic tubes are used to replace the valves that would normally let blood in and out of the ventricles. The main section of the device, which features two artificial ventricles, is then plugged into the plastic valves to complete a synthetic heart system.
The implant itself does not contain any motors or electrical parts, but is, instead, run by a pneumatic pump and power supply that must be carried outside the body. This portable unit, which is the first of its kind, is connected to the artificial heart by pneumatic tubes that pass through the skin. These tubes send pulses of air into two expandable, balloon-like sacs in the artificial ventricles, forcing out blood in much the same way that a beating heart would. The driver unit weighs just under 14lbs and, while relatively heavy, it offers artificial heart patients an unprecedented level of freedom.
Is this the first artificial heart?
There have been other artificial heart devices, but these have mostly been designed to remedy a single damaged ventricle or to be used in patients staying in hospital. Indeed, as far back as the 1980s doctors used the Jarvik-7 Artificial Heart for short-term treatment. The Jarvik-7 was used as the basis for much of this new device. However, this case is reported to be the first time that a UK patient has been given a full implant that has allowed them to return home, a feat that has already been achieved in some other countries.
Can the heart be used indefinitely?
No, the device is only intended to be a short-term solution. Although initially designed for permanent use, the TAH is approved as a “bridge to transplant” device, meaning it can be used to replace a badly failing heart in the period until a suitable donor heart becomes available. People who have the device implanted are expected to remain on a transplant list until a donor becomes available. In this case, the patient had “end-stage” heart failure, a potentially fatal problem. In such cases, the risks of getting a bridging implant are fewer than the risks of going untreated while waiting for a donor heart.
However, while only a temporary solution, the artificial heart is said to provide the body with an immediate blood flow of up to 9.5 litres a minute. This improves the mobility of some patients with limited physical ability caused by heart failure.
What conditions could it be used for?
The TAH is used for “end-stage biventricular heart failure”, which is severe heart failure affecting both ventricles of the heart. It is a condition that can develop after the heart has been damaged or weakened by disorders such as coronary artery disease, heart attack or cardiomyopathy. Heart failure occurs when the heart can no longer pump enough blood to sustain the body, causing the organs, such as the kidneys, liver and brain, to be starved of oxygen and the nutrients they need to function properly.
Symptoms of heart failure include shortness of breath, persistent coughing, palpitations as the heart beats faster to make up for its loss of pumping capacity, excess fluid (oedema) and fatigue. Inadequate blood flow means tissue can die and vital organs suffer permanent damage. The design of the device also allows the patient’s body to determine the blood flow required from the device based on his or her activity level.
What will happen to the patient next?
The patient, who received his implant on June 9 2011, will be closely monitored for risk of his body rejecting the device and the risk of infection. The device gives the patient more time to find a suitable heart donor, but a transplant must still be performed. In the interim, the patient is reported to be doing well and has returned home to his family.
Papworth Hospital, where the procedure was carried out, is currently the only UK hospital certified to use the TAH device. Although the device is suitable for use only in certain severe cases, this high-profile case has made international news and is sure to raise the profile of the TAH implant. Time, and the results of further research, may lead to greater use of this intriguing device in future.