Aspirin no help to one in four heart patients

PUBLISHED : Thursday, 09 August, 2007, 12:00am
UPDATED : Thursday, 09 August, 2007, 12:00am

Drug resistance raises coronary risk

One in four coronary artery disease patients is resistant to aspirin's ability to prevent blood clotting, meaning they are four times more likely to suffer heart attacks or strokes than patients who respond to the cheap pills, a University of Hong Kong study shows.

About 50,000 people in Hong Kong have coronary artery disease, of whom 90 per cent need to take aspirin every day to protect their hearts.

But a study conducted by the university's department of medicine between 2002 and 2004 showed 125 of 468 patients with stable coronary artery disease were aspirin-resistant, meaning the drug did not reduce the risk of blood clots.

The researchers monitored the patients' health and found 15.6 per cent of the aspirin-resistant people suffered heart attacks, strokes or other serious health problems during that period, compared with 5.3 per cent of those responsive to aspirin.

The risk of patients resistant to aspirin suffering a heart attack were 3.8 times that for patients responsive to the pills. Strokes were 4.1 times more likely. 'We are not sure what causes aspirin resistance but we do know that older people and women are more likely to be aspirin-resistant,' said Chen Wai-hong, honorary clinical assistant professor in the department.

He said patients should take pills at the times prescribed to avoid developing resistance to drugs.

'Apart from aspirin, there are two other drugs that prevent blood clotting for coronary artery patients, but more research has to be done before we can recommend aspirin-resistant patients alter their medication,' Dr Chen said.

Patients should not change their medication themselves, he said, adding that people might suffer side effects from other drugs and build a resistance to the medication.

The medic noted that the alternative drugs were usually more expensive than aspirin, with each pill costing more than HK$10.

Dr Chen said public hospitals did not routinely check patients for aspirin resistance but private hospitals and laboratories offered a quick test.

According to the government's Centre for Health Protection, heart diseases were the second most common cause of death in Hong Kong in 2005, killing 5,868 people.

Among them, 4,781 died of ischemic heart disease, where the blood supply to the heart is reduced because of blocked blood vessels.

Aspirin is the most common means of preventing blood clotting.

It can reduce by an average of 22 per cent the chance of blood supply being reduced to the heart in patients where the arteries are clogged with fat.

The common side effects of excessive aspirin use include ulcers and bleeding in the stomach and, for women, heavier periods.

Doctors recommend people have healthy diets and exercise regularly to avoid developing heart disease.

Heart of the matter

Deaths per 100,000 people in Hong Kong from coronary heart diseases in 2005 60