New way to stop the heart could help bypass surgery patients

Main Category: Public Health
Article Date: 18 Sep 2003 - 0:00 PDT


Heart bypass surgery patients could have a better chance of a full recovery thanks to a new way of stopping the heart during surgery.

The current way of stopping the heart during surgery is to flood it with potassium ions. However, this can cause permanent damage.

Geoffrey Dobson and Michael Jones (James Cook University, Townsville, Australia) have been testing a new method on animals. Results look promising for humans. Their method keeps potassium levels normal - this prevents injuries to the muscle cells and to the vessels that carry blood to the heart.

The distribution of ions in resting muscle cells generates an electric potential. When the membrane opens ions flow across the membrane and depolarise the cells. If you flood the heart with potassium ions the cells freeze.

What Dobson and Jones have done is to freeze the resting heart with two drugs - adenosine and lignocaine (USA - lidocainein). Adenosine opens the channels that transport potassium ions in and out of the cell. Lignocaine blocks sodium ion channels.

According to Jakob Vinten-Johansen (a cardiovascular physiologist at Emory University in Atlanta, Georgia, USA) there are two ways to stop a heart. You either let it run out of gas, that's the potassium infusion - or you don't even turn it on. This is what Dobson has done.

If you perfuse rat hearts with potassium for two hours, only 50% start beating again afterwards. However, if you perfuse rat hearts with adenosine and lignocaine for two hours, they all start beating again afterwards (although at only 70% of their previous beating ability).

Dobson found that with a dog which had been given a single five-minute infusion of the drugs, its heart stopped for an hour and then started beating again spontaneously (at 100% of its previous beating ability). Moreover, the heart was kept at body temperature.

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