A non-invasive scan used to determine the extent of plaque buildup in the heart accurately predicts the likelihood of heart attack or death over a 15-year period, a research team led by Weill Cornell Medical College investigators reported July 6 in the Annals of Internal Medicine. Doctors can use this information to intervene if a patient is shown to be at risk for heart disease but not yet showing any symptoms.
"All high-risk individuals — irrespective of their symptom status — should be considered for this study. It is like a mammogram for the heart," said Dr. James K. Min, director of the Dalio Institute of Cardiovascular Imaging at NewYork-Presbyterian Hospital and Weill Cornell Medical College, and a professor of radiology and of medicine at Weill Cornell. "If physicians can accurately predict who is at risk, they can intervene earlier and more aggressively and hopefully prevent patients from ever having a heart attack."
Heart disease is the number one cause of death in the United States, killing 40 percent more people than all types of cancer combined. But while there are routine screens for many types of cancer — like breast and prostate — there isn't a universally adopted test used to check for heart attack risk in people not exhibiting any symptoms associated with heart disease. The investigators say their findings demonstrate that the coronary artery calcification test, a five minute-long procedure that examines the total amount of calcified plaque buildup in the heart arteries, should fill that void.
"This test predicts the risk of heart attacks better than any other diagnostic heart test that we have, especially in asymptomatic patients," Dr. Min said. "It embodies the goal of precision medicine, namely, to precisely identify and exclude the patients who have or do not have disease that places them at heightened risk of heart attacks."
While previous studies have connected coronary artery calcification test results and long-term patient prognosis, this study is significant for its size and scope: It looked at the largest patient population over the longest period of time.
Investigators, who also came from Emory University School of Medicine in Atlanta and Cedars-Sinai Medical Center in Los Angeles, reviewed the medical records of 9,715 patients in the area surrounding Nashville, Tenn., who were referred by their primary care physician to a single outpatient clinic from 1996 to 1999. Physicians at the clinic gathered basic demographic information along with patients' cardiac risk factors, including history of diabetes, elevated cholesterol levels, documented high blood pressure or family history of coronary heart disease.
All patients then underwent a coronary artery calcification test. The Calcium — or Agatston — Score goes from zero, representing a normal scan with no calcium at all, up to more than 1,000. Within the study, the participants were grouped by their resulting number in the following configuration: zero, one-10, 11-99, 100-399, 400-999 and more than 1,000.
"More than 1,000 is considered the worst case scenario, with imminent risk," Dr. Min said. "But over 400 is severely elevated. It's all very linear and predictable."
After collecting this de-identified data, the investigators tracked the status of all participants through the National Death Index, a central computerized index from the National Center for Health Statistics. The investigators followed the patients for a mean of 14.6 years.
With the Calcium Score and cardiac risk factor variables, investigators calculated the risk that participants would die for any reason, not just because of a heart attack, called all-cause mortality. They then compared this long-term prognosis against what actually happened, and found that the Calcium Score was highly predictive of all-cause mortality. During the 15 years, 936 study participants died at the rate of 3, 6, 9, 14, 21 and 28 percent, respectively, compared to the increasing Calcium Scores.
So what does the data mean? "In all asymptomatic patients, someone with a score of zero has a minimal risk that they will die from any disease in the next 15 years," Dr. Min said. "It's a very long-term warranty period.
"On the other hand, if a patient has any calcium in his heart, he or she is at risk. We must intervene quickly and aggressively for patients' future health because that risk never goes away," he continued. "We have medicine that saves lives; we just need to identify earlier the right patients so that we can get them the right treatments."