People with heart disease may be able to reverse their condition by taking higher doses of powerful cholesterol-lowering drugs, research suggests.

Doctors have known for some time that statin drugs, which are used to counter cholesterol, can check the progress of heart disease, but for the first time a significant number of patients have effectively had the clock turned back on the progression of coronary heart disease.

The team behind the research, unveiled yesterday in Atlanta by the American College of Cardiology, believe they may have found the "holy grail" in their quest to treat one of the world's biggest killers. Patients in the US study, which was paid for by the drug company AstraZeneca, not only got their "bad cholesterol" to the lowest levels ever achieved, but also saw blockages in their blood vessels shrink. "The holy grail has always been to try to reverse the disease," said Steven Nissen, the cardiologist who led the nationwide experiment, adding that the research could point doctors in the right way.

Elizabeth Nabel, the director of the UK's National Heart, Lung and Blood Institute, said: "This is a paper to take seriously. It's another chapter in the story, a proof of principle." Two-thirds of the 349 people in the study saw a reduction in their heart artery build-ups when they took the maximum dose of Crestor, a statin drug manufactured by AstraZeneca.

In Britain, cardiovascular disease is the largest cause of death, claiming the lives of 238,000 people. About 1.8 million adults take statins in England and Wales.

However, the research team said yesterday that their study "does not alter our assessment that Crestor has unique risks without evidence of unique benefits". They added that the drug should not be prescribed - especially at the doses used in their study - unless lower doses and other drugs failed to help.

Crestor's safety has been questioned by the Lancet magazine and the influential American consumer group Public Citizen, which claimed it has more side effects than its competitors. Some reports have also linked the drug to to higher rates of serious muscle problems and kidney damage, especially among Asians. Last year he US government's Food and Drug Administration threw out a petition to have Crestor banned, but did order the drug to carry a warning on its label.

Yesterday's announcement saw a rise of 2.3% in AstraZeneca's share price. Despite a huge marketing push, Crestor has not challenged the leadership of Pfizer's statin class drug, Lipitor, the world's best-selling pharmaceutical. Crestor had sales last year of $1.26bn (£724m), compared with Lipitor's $13bn.

Even though no major safety problems emerged in the study, doctors warned it was too small to detect rare side effects.

They found Crestor not only reduced "bad cholesterol" levels - but also raised the levels of "good cholesterol". They believe this dual effect may be what caused blockages to shrink.

Dr David Williams, of Rhode Island cardiology centre, who had no part in the study, described the results as "very, very exciting", but another physician, Dr Roger Blumenthal of Johns Hopkins University, suggested the researchers should have tested Crestor against a lower dose of another statin. The journal will publish the study next month.

Statins: anatomy of a wonder drug

Statins have been hailed as a wonder of modern medicine; they reduce LDL or "bad cholesterol" while slightly raising levels of HDL or "good cholesterol". They work to block the production of cholesterol by inhibiting an enzyme in the liver called HMG-CoA reductase.

By reducing cholesterol levels, they help to prevent heart attacks and strokes and are estimated to save between 6,000 and 7,000 lives every year in England and Wales.

Some studies have also suggested that the drugs may be useful in the treatment of other conditions such as multiple schlerosis and Alzheimer's disease.

However, some statins have rare but serious side-effects. Around one in every 1,000 patients develops inflammation in the muscles, which can lead to serious kidney problems.

The people most likely to benefit from statins are those with a family history of coronary heart disease, those who smoke, or who gave up only recently, and those who are overweight or of South Asian ethnicity. However, most doctors agree that the best way to lower cholesterol is through diet and exercise.

Statins such as Lipitor, Zocor and Pravachol have become top-selling drugs - outstripping even Viagra sales.