"Treatment guidelines suggest that nearly half of those over age   nearly  million people in the United States  at least consider a cholesterol httphealth.nytimes.comhealthguidesnutritioncholesteroloverview.htmlinlinenytclassifierlowering statin to reduce heart attack risk. But a new large study of people who had an inexpensive heart scan found that half of those who were statin candidates had no signs of plaque in their heart and very little chance of having a heart attack in the next decade. Some cardiologists say the results could go a long way toward helping patients make a more informed choice about whether to begin taking the drugs. The test is a CT scan httphealth.nytimes.comhealthguidestestctscanoverview.htmlinlinenytclassifier that looks for calcium httphealth.nytimes.comhealthguidestestserumcalciumoverview.htmlinlinenytclassifier in coronary arteries a signal that plaque is present. It used to be expensive  about   but now typically costs between  and . Still it is generally not covered by insurance and so is not often used to assess risk. The Xray httphealth.nytimes.comhealthguidestestxrayskeletonoverview.htmlinlinenytclassifier dose is about that of a mammogram httphealth.nytimes.comhealthguidestestmammographyoverview.htmlinlinenytclassifier. Advocates for the scan say it should be used to derisk people. It can let those who do not want to take statins know whether their chance of a heart attack is actually extremely low. Maybe this is a tool to actually do less said Dr. Harlan M. Krumholz a Yale cardiologist and senior author of the paper httpcontent.onlinejacc.orgarticle.aspxarticleID published on Monday in the Journal of the American College of Cardiology. For those who have no objections to taking statins there is no need for a heart scan Dr. Krumholz said. But for those who are reluctant to take them he said I am willing to use this to refine their risk estimate. Others say the test can lead to an array of other medical problems some of which are gravely serious. The only reason to do things is to feel better or to live longer said Dr. Peter Libby a cardiovascular disease specialist at Harvards Brigham and Womens Hospital. With the scans he said that has yet to be established. Heart researchers have long known that plaques in coronary arteries start out as pimplelike bumps but get waxy and hard and filled with calcium as time passes. Calcium shows up as white flecks in CT scans. The hard plaques are not the dangerous ones  it is the softer ones that rupture and cause a heart attack. But the amount of calcium in arteries can give a good idea of the presence or extent of coronary artery disease. Dr. Krumholz and Dr. Khurram Nasir a preventive cardiologist at Baptist Health South Florida who conceived the new study reasoned that research on heart scans had not been designed to help doctors make treatment decisions they face today. Current guidelines have vastly increased the number of people who are eligible to take statins. Many people though are reluctant to take them. So the investigators asked could a scan identify those whose actual risk is lower than what was calculated The study subjects were nearly  men and women ages  to  and included blacks whites Hispanics and Asians who were recruited in  through . According to todays guidelines half had risk scores high enough that a statin would be recommended or should be considered. But guidelines then were more conservative and in accordance with them the subjects did not take the drugs. All had heart scans and half had no calcium visible on the scans. The subjects were followed for  years. It turned out that the actual incidence of heart attacks or disabling chest pain httphealth.nytimes.comhealthguidessymptomschestpainoverview.htmlinlinenytclassifier in those with zero calcium was half or less than what the risk calculator predicted. For example a person who according to the current risk calculator has a  percent risk of a heart attack in the next decade should take a statin the guidelines say. But if that person has a calcium score of zero the actual risk turned out to be  percent below the . percent threshold for recommending a statin according to the guidelines and below the  percent risk for considering a statin. Dr. Nasir said he has been using the studys findings in his clinic. First he asks patients for whom statins are recommended according to the current guidelines if they would want to avoid taking the drugs if they turn out to have a calcium score of zero and an actual risk of less than  percent. Most tell him that they would. He then sends them for a scan.  But the study was observational not the highest level of evidence. The problem critics say is that there has never been a rigorous study randomly assigning people to a change in treatment based on a scan and demonstrating that the change improves outcomes. Dr. Libby of Harvard for one is leery. Although very few heart attacks may have occurred over a decade in people with no calcium he said noncalcified plaques may be developing that could cause trouble. And the time span for worrying about a heart attack is more than a decade he said. One problem with the scans is what doctors call incidentalomas  unexpected incidental findings like lung nodules httphealth.nytimes.comhealthguidessymptomsnodulesoverview.htmlinlinenytclassifier. The new study reported such findings in  percent of patients but radiologists have reported incidences in the double digits. All too often these findings start patients on a diagnostic odyssey getting tests and biopsies sometimes exploratory surgery only to find that there was nothing wrong. Routine heart scans of tens of thousands of people would uncover a not negligible number of incidentalomas Dr. Libby said. Then there will be the people with no symptoms of heart disease who turn out to have a high calcium score. Dr. Libby explains what often happens next The doctor suggests an angiogram httphealth.nytimes.comhealthguidestestarteriogramoverview.htmlinlinenytclassifier an Xray of the arteries. It shows one of the arteries is  percent blocked. The cardiologist inserts a stent httphealth.nytimes.comhealthguidessurgerystentoverview.htmlinlinenytclassifier a wire cage to keep the artery open although many researchers doubt stents httptopics.nytimes.comtopnewshealthdiseasesconditionsandhealthtopicsstentsindex.htmlinlinenytclassifier will prevent heart attacks in symptomless people on todays medical therapy. Now the patient with the newly inserted stent has to take a powerful anticlotting drug and aspirin for at least the next year. Because the drugs make bleeding more likely the patient notices blood in his stool. Before he can have a colonoscopy httphealth.nytimes.comhealthguidestestcolonoscopyoverview.htmlinlinenytclassifier to check on the blood he has to stop the anticlotting drugs for a week. But without them he risks getting a clot at the site of the stent and having what could be a fatal heart attack. Now we have taken a healthy person asymptomatic and turned him or her into a patient Dr. Libby said. But others like Dr. Daniel Soffer a general internist at the University of Pennsylvania see a real benefit in using heart scans to derisk patients. All the other biomarkers get blown away compared to the calcium score he said adding that it is far and away the best marker of risk. The new study justifies to him a practice he began years ago of using scans with the belief that they could be better than a risk calculator for some patients. One of his patients Rena H. Barnett  had a scan a decade ago. Her mother died of a heart attack and Mrs. Barnett knew her level of LDL cholesterol the bad kind was very high at . But she said statins and other cholesterollowering drugs made her depressed and made her muscles ache so much she could not get out of bed in the morning. She tried lowering her LDL level by becoming a vegetarian but it did not budge. Relaxation with yoga did not help. But when Mrs. Barnett had a heart scan she learned that her calcium score was zero. Five years later she had another scan. Zero again. For now Mrs. Barnett is not taking anything to lower her cholesterol levels. Its not that I feel good about it. It would be nice to have it lower she said. But her anxiety has lifted."