A new type of pump to help failing hearts will undergo clinical trials in autumn 2004 in the UK. Its design is intended to solve the problems of mechanical failure and blood clotting that have bedevilled artificial hearts and pumps since they were invented.

The pump also has a curious side effect: people implanted with the device have no pulse.

The VentrAssist, which is made by Australian company Ventracor, is of a type known as left ventricular assist devices. LVADs are not designed to replace the heart but are implanted alongside it under the rib cage. They augment the pumping action of the left ventricle – the heart’s main chamber and the one that is responsible for 90 per cent of heart failure cases.

Most LVADs attempt to mimic the way the heart works, but their complicated design makes them prone to failure, and they have a tendency to make blood pool and clot, leading to strokes. That means LVADs are usually only used as a last resort for patients waiting for heart transplants.

What makes the VentrAssist different is that it only has one moving part, a spinning impeller that drives a continuous stream of blood. That means the pulse is replaced by a gentle whirling noise that patients describe as similar to the sound of a washing machine. More importantly, the device prevents blood from stagnating, reducing the risk of clotting.

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