'Safer way' to stop heart during op

Stopping the heart carries risks

Scientists say they have found a safer way to stop the heart during surgery.

Sometimes surgeons have no option but to stop the heart to perform surgery, as it can be very difficult to operate on a moving target.

However, a commonly used method, flooding the heart with potassium ions, can cause permanent damage.

A team from James Cook University in Australia has developed a safer alternative using two drugs, adenosine and lignocaine.

The beating of the heart is controlled by an electrical current generated by the movement of chemicals within the tissues of the organ.

Flooding the tissue with potassium ions effectively sabotages this process, and stops the heart beating.

However, raising potassium levels can make the heart muscle cells and vessels vulnerable to injury.

The new technique, reported in New Scientist magazine, uses adenosine to achieve the same effect without the same risk of injury.

Tests

Experiments on rat hearts showed that when they were flooded with potassium for two hours, only half started beating again afterwards.

However, when rat hearts were perfused with adenosine and lignocaine for four hours, they all started again, although they only retained about 70% of their previous pumping ability.

The researchers also found that a single five-minute infusion of the drugs was all it took to stop the heart on an anaesthetised dog for an hour. It started beating again spontaneously, and appeared to work just as well as before.

In addition, the heart was kept at body temperature, whereas in open heart surgery the body is usually cooled to help prevent damage.

Researcher Dr Jakob Vinten-Johansen, from Emory University, Atlanta, who collaborated with the Australian team, told New Scientist: "The injection seemed to put the heart in a state of suspended animation, something you'd never see with potassium."

Improvements

Mr Ragheb Hasan, a cardiologist at the Manchester Heart Centre, told BBC News Online that techniques to protect the heart from damage had become increasingly sophisticated, and that many operations were now carried out without the need to stop the heart.

In fact, Mr Hasan said he performed all his heart bypass operations - the most common form of open heart surgery - on the beating organ.

He said: "Stopping the heart is required when operations are carried out on the inside of the heart.

"If this technique shows better protection for an arrested heart then it will have an impact on such operations.

"However, this research is still in its early stages, and we need to find out how it would work on bigger animal hearts."

The research is due to be published in the Journal of Thoracic and Cardiovascular Surgery.