Pumping Marvellous

The world’s first wireless heart pacemaker was unveiled Monday. The device dramatically reduces surgical time so reducing cost and the chances of infection.

Andrew Diston, Head of Global Medical Technology at Cambridge Consultants which collaborated with start-up company EBR Systems to develop the system said the device, Wireless Cardiac Stimulation system (WiCS), solves two problems.

“Conventional pacemakers have to have a wire threaded through into the ventricle. That is very hard to place. And secondly we can place the electrode in a much better place and so get better results.” Pacemakers are in two parts, a pulse generator, with its associated power
supply, and an electrode that stimulates the cardiac muscle that is placed in  the heart. Such devices require three leads into the heart, one of which involves painstakingly threading a lead through a difficult and complex route running from the right atrium of the heart, out of the heart and into the coronary sinus, a vasculature structure on the outside surface of the heart to the left ventricle.

Chance of lead failure and infection

A pacemaker/defibrillator device is connected to the leads which are used to sense heart activity and to deliver electrical stimulation through electrodes at the end of the leads. The electrical stimulation applied to the right and to the left ventricles synchronizes the heart’s contraction in a way that improves overall cardiac function in heart failure patients. However, added to the difficulty of the procedure itself is the chance of
lead failure and infection. WiCS uses a lead-less electrode to convert mechanical energy, wirelessly transmitted from an ultrasonic pulse generator, into electrical energy which is used to pace the heart’s left ventricle.

“It is the same technology as was found in an old stylus. We beam the energy using ultrasound. That is picked up in the electrode and using piezo technology, the ultrasound is converted into an electrical signal,” said Mr. Diston.

Hope to get approval in 2012

“Provided you focus the energy onto the electrode it is very efficient.” “The device is currently in clinical trials in a number of places across
Europe,” said Mr. Diston. “They will carry on through 2012. We hope to get approval in 2012 for a European launch, and then will take the technology to America.” This, first generation device, is used to pace the heart as part of Cardiac Resynchronization Therapy. WiCS works in conjunction with a conventional pacemaker/defibrillator, sensing the electrical pacing pulse of the pacemaker from the right ventricle.

Mr. Diston said that future devices would be able to work without a conventional pacemaker being present.

Image via Wikipedia

The Total Artificial Heart

We were wondering whether to put this on the site and whether it would be useful to anybody as the TAH (Total Artificial Heart) is only currently available to patients who have end stage heart failure with bi-ventricular failure and is only available currently at Papworth which has the certification to carry this out.

Anyway here is what it does -

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.

Can the heart be used forever?

No, the device is only intended as 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 problem that can be potentially fatal. In such cases, the risks of getting a bridging implant are less 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.

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 Matthew Green 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.