New test helps pin down best heart-attack treatment

Heart-attack patients with a characteristic electrical abnormality are more likely to die and should be considered for more aggressive treatment, new Auckland-based research suggests.

Published in the Lancet, a leading British medical journal, the international study led by cardiologist Professor Harvey White found that patients who had the abnormal "Q wave" pattern during a heart attack were up to 50 per cent more likely to die within 30 days.

Small electrical currents in the heart trigger its beats. Q waves are changes in the electrical pattern which usually occur as heart muscle dies.

One of the study's authors, Auckland City Hospital cardiologist Dr Ralph Stewart, said yesterday its results could help decide which heart attack patients should be given powerful drugs to dissolve blood clots and which should be considered for angioplasty. The findings might lead to more angioplasties.

Heart attacks are normally caused by a blood clot blocking a heart artery. Angioplasty is performed using a removable inflatable balloon and a small metal device called a stent. The balloon and stent are inserted through a blood vessel from the groin and the stent is left in the artery.

Dr Stewart said the traditional way of deciding which treatment to give was the time elapsed since the patient began to have chest pain.

"If that time is shorter, and the cut-off is usually about three hours, then a clot-dissolving drug is probably just as good as using a balloon [and stent] to open up the artery.

"We've found that often if the delay is longer than three hours and you are able to take the person to the catheterisation laboratory and do angioplasty that is the best thing to do."

But the study showed that pathological Q waves, identified by wiring the patient to an electrocardiograph, were a better predictor - than the time since pain started - of who would die within a month.

"We think it reflects the duration of the heart attack. The longer it goes on the more likely you are to have Q waves."

"The implications of this are related to the treatments we give. It's important to identify which treatments should be given as soon as the person comes to hospital and the electrocardiogram provides a simple way of identifying who might benefit most from angioplasty rather than clot-dissolving medication.

"Previous studies have shown angioplasty can reduce mortality, particularly in persons who present to hospital later."

Hospitals have been increasing the number of angioplasties, reducing the need for heart artery bypass operations.

Angioplasty was more expensive than clot-dissolving treatment, but many patients given the drugs at first ended up having angioplasty as well.