A gentle squeeze

University of Leeds PhD student David Keeling shows the web material that will be used in the development of the heart-assist device. The biocompatible material, which is not rejected by the body, detects when the heart wants to beat, and assists it by contracting and expanding

A new device could put the beat back into weak hearts – and free patients from a lifetime of anti-rejection drugs.

Current heart-assist devices suck blood from ventricles and expel it into downstream vessels. While these have been successful in prolonging the lives of heart patients, they come into contact with the blood stream and hence require life-long drug therapy to suppress the immune system and prevent blood clotting. In addition, many of these devices can damage cells within the blood, increasing the chance of clots forming.

An ingenious new device being developed by engineers at the University of Leeds provides a less invasive alternative. The team has developed a specially-woven web made from biocompatible material that will not be rejected by the body.

The webbing wraps around the heart and, therefore, does not come into contact with the blood stream. Inbuilt sensors recognise when the heart wants to beat and trigger a series of miniature motors which cause the web to contract – increasing the internal pressure and assisting the heart to pump the blood around the body.

The team consists of Peter Walker, who devised the original concept, and Martin Levesley from the University’s School of Mechanical Engineering, cardiac consultants Kevin Watterson and Osama Jaber from Leeds General Infirmary and engineering PhD student David Keeling.

“It’s a really simple concept that works in the same way as when you squeeze a plastic bottle, forcing the liquid inside to rise,” says PhD student David Keeling who has built a special rig to test the device.

The device is currently a prototype, with the team using a computer simulated model of the human blood flow circuit coupled to David’s mechanical rig. The rig replicates the motion of the heart within the simulation under different conditions, and allows the team to test their web device.

The group is currently testing their latest prototype, in order to refine design and assist strategies.

“We’ve been looking at finding the optimum timing to trigger and also length of the compressive squeeze,” David says.

Once perfected, the team intends to simulate the effects of different heart diseases to gauge the potential success of the device.

Potential uses for the device are huge. As well as offering support to people suffering from heart and valve problems, the device could also be a bridging aid to patients as they wait for transplants, providing them with a better quality of life.

“Recent research has found that with some heart diseases, supporting the heart for a short period with an assistive device reduces the work-load on the heart and allows it to rest and recover,” David says.

“Our device also allows for a controlled relaxation of the heart muscle, which means that it’s being supported throughout the whole heartbeat process. It’s the same as when you pull a muscle in any other part of your body, rest can often be the best therapy,” he added.