Professional Engineering

Heart disease accounts for almost half of all deaths in the developed world. The most effective treatment is still heart transplants, but the demand for donor organs far exceeds supply. To address this imbalance, engineers at the University of Leeds have embarked on a project that could transform the way cardiovascular illnesses are managed.

The academics, from the school of mechanical engineering, have developed an intelligent device that could be wrapped around a damaged heart, applying compression to boost blood flow. They have also built a mechanical heart simulator so they can test the device over long periods to measure its performance.

“It’s an exciting development,” says Dr David Keeling, the lead engineer on the project. “The heart-assist device effectively acts as an artificial muscle wrap, surrounding the ventricles and squeezing in synchronisation with the heart’s native rhythm.

“We have also developed what we believe is a realistic, reliable, and reconfigurable testing environment to advance and improve the device without the need for animal testing.”

The intelligent ventricular-assist device (iVAD) has been designed to function as an artificial muscle wrap that assists the failing heart by applying compressive force around the external surface of the ventricles. This cyclic “squeezing” action augments heart muscle efforts, improving output by as much as 25%.

Keeling and his colleagues needed to physically apply the iVAD to a heart simulator to measure its compressive efforts, so a realistic in vitro testing environment was imperative for development. Approaches used for other heart-assist devices have involved either mechanical mock circulatory systems or extracted hearts metabolically supported by another animal’s blood flow. 

“Traditional methods use excised hearts or bulky hydraulically or pneumatically driven systems – we preferred neither method,” says Keeling. “We wanted to come up with a ‘mechatronic’ version. So we created a unique hardware-in-the-loop (HIL) heart simulator that combines a real-time software blood-flow model with a physical 3D mechanical heart.

“The hardware is a mechanical heart that feeds into a simulated loop which has a numerical model of blood flow throughout the body. The heart rhythm simulation is then mimicked by the mechanical heart. 

“We can then put the assist device onto the mechanical heart to squeeze it, allowing us to measure the compressive pressure. That pressure gets fed into a simulation, and from that we can work out how effectively the device would assist the patient.”

The researchers wanted the heart simulator to be reconfigurable so that it could physically and haemodynamically replicate different patient groups, illnesses, and
animal models. This adaptability could reduce the need for animal testing, because the heart simulator could be used for prolonged trials of prototype iVADs and provide information on physiological effects.