Researchers hunting for the next blockbuster heart drug say levels of enzyme activity checked in their study can help to predict a person's risk of coronary heart disease.
"It's a new risk factor," said Professor Harvey White, research leader and cardiologist at Auckland City Hospital Green Lane Cardiac Service.
At present the main risk factors for heart disease include smoking, high blood pressure, high cholesterol, age, obesity, ethnicity and family history.
Professor White, following publication of a study in the Journal of the American Heart Association, said the test for the enzyme's activity merited being included in standard heart tests, but proof of an effective drug specifically to block its effects were needed first.
The enzyme is called Lp-PLA2, short for lipoprotein-associated phospholipase A2. Its role in cardiovascular disease has been under the microscope for a decade.
Professor White and colleagues re-analysed data from a trial in heart-attack and unstable-angina patients of a statin drug called pravastatin; statins are prescribed to reduce cholesterol.
"It is well understood," he said, "that reduction in LDL [bad] cholesterol is a key mechanism by which statins reduce risk. This study proves that other mechanisms are also important - reduction in Lp-PLA2 activity during the first year may account for over half of the benefits of pravastatin in the ... study.
"There was a 24 per cent reduction in death from coronary heart disease and a 22 per cent reduction in overall mortality."
Professor White is co-chairman of a 15,000-patient international trial of darapladib, a drug from GlaxoSmithKline intended to inhibit the activity of the enzyme and reduce the rate of heart attacks and strokes in patients with a history of problems.
Placebo or not, stroke victim's out to enjoy life
Long-term heart and stroke patient Paul Steele reckons his medicine cocktail contained a new drug being tested in an international trial.
But he and his doctors will never know if he received the active drug darapladib or identical-looking placebo dummy pills during the four years he was on the trial.
At first Mr Steele thought he was in the placebo group. When he finished taking the drug, however, he noticed slight changes he thought indicated he had been on the medicine intended to inhibit the Lp-PLA2 enzyme.
Mr Steele, 76, and his wife Jenny own and operate holiday apartments at Ahipara near Kaitaia in Northland.
He suffered his first cardiovascular trouble, a series of mini-strokes, 20 years ago. He received treatment for that and later found out his heart's arteries were in a bad state too.
"I had a heart attack five years ago and another one in May this year. I had a stent put in five years ago but it didn't work."
Following the most recent heart attack Mr Steele was told to continue with his various medications, which include drugs to reduce cholesterol, high blood pressure and the risk of blood clots.
He changed his diet and keeps up an active lifestyle running the accommodation and taking clients fishing on Ninety Mile Beach.
"I enjoy life," said Mr Steele.
He said cardiologist Professor Harvey White had urged him to join the darapladib trial, telling him, "People in studies do better".
"I think the people who look after you at Auckland City Hospital in the cardiology department are switched on, very caring and do their utmost for their patients," Mr Steele said.
What is it?
• The enzyme called Lp-PLA2 is produced by inflammatory cells in the blood.
• It is mainly carried around the body by LDL "bad'' cholesterol.
• Higher activity levels of the enzyme are linked with increased risk of heart attacks and strokes.
• Activity levels of the enzyme are higher in men than women.
• Levels track higher with elevated levels of bad cholesterol.