Adding a single pill to standard treatment for coronary artery disease can save lives and reduce heart attacks, doctors said Sunday.

New research has shown that a common blood pressure pill could save hundreds of thousands of coronary patients from dying from heart disease or suffering a heart attack over a four-year period.

The study, presented at the annual meeting of the European Society of Cardiology in Vienna, is the largest experiment ever to test the power of so-called ACE inhibitor drugs -- already recommended for coronary heart patients over 55, those with heart failure and others at high risk of dying from complications, such as people with diabetes or high blood pressure.

'The biggest part of the jigsaw are the people that are left,' the study's director, Dr. Kim Fox of the Royal Brompton Hospital in London. 'There is a much bigger pool of patients out there who are dying of coronary disease even though they feel quite well.'

Fox described the study as a milestone in the treatment of heart disease because it proved for the first time that an ACE inhibitor can have lifesaving benefits even in younger coronary patients and those considered to be at low risk of complications.

Experts said the results will drastically increase the number of people taking ACE inhibitors.

The four-year study, conducted on 12,218 adults with coronary heart disease from 24 European countries, found that patients who added one type of ACE inhibitor, perindopril, to their daily medication had a 20 percent lower risk of dying from a heart attack or stroke or of having a survivable heart attack than those who did not take the extra pill.

Their risk of being admitted to the hospital with heart failure was 39 percent lower. In the study, perindopril prevented one person from dying of a heart attack or stroke or from having a survivable heart attack out of every 50 people given the drug for four years.

Dr. Robert Bonnow, past president of the American Heart Association, said the findings were significant and definitive.

'One final question -- that will require additional trials -- is whether ACE inhibitors might also be beneficial in even lower risk populations, such as patients with several risk factors for coronary artery disease but without established coronary artery disease,' said Bonnow, a professor at Northwestern University in Evanston, Illinois, who was not involved with the research.

The study was financed by Servier, the French pharmaceutical company that makes the pill used in the research.

Perindopril is known as Aceon in the United States and as Coversyl in Europe and elsewhere. Other ACE inhibitors include Altace, Accupril, Monopril and Zestril.

Coronary artery disease is the most common form of heart disease, which is the leading killer in the Western world. About 13 million Americans and 20 million Europeans have it, experts estimate. The American Heart Association predicts that 1 million Americans will have a coronary attack this year.

Over the past few decades, prevention efforts and new drugs have substantially improved the outlook of these patients. However, the risk of complications is still high. Despite treatment with cholesterol-lowering drugs, aspirin, and beta blockers, the disease usually progresses.

'Any improvement that we can make to this disease will have a huge impact in the delivery of health care throughout the Western world,' Fox said.

Scientists now believe angiotensin converting enzyme, or ACE, inhibitors -- first used to treat hypertension -- do more than just lower blood pressure. They may have an effect on the arteries themselves.

The pills have few serious side effects. The most common and annoying is a persistent cough, which occurred in about 4 percent of patients in the study.