Coronary artery calcification test predicts long-term risk of death in asymptomatic patients

A short, non-invasive scan used to detect coronary artery calcification (CAC) accurately predicts the likelihood of heart attack or death over a 15-year period, a research team reported 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 James K. Min, MD, director of the Dalio Institute of Cardiovascular Imaging at NewYork-Presbyterian Hospital and Weill Cornell Medical College in New York, 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."

While previous studies have connected CAC 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.

Heart disease is the number one cause of death in the United States, killing 40% 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 CAC test, a 5-minute-long procedure that examines the total amount of calcified plaque buildup in the coronary 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."

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, TN, 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, and family history of coronary heart disease.

All patients then underwent a coronary artery calcification test. The Calcium—or Agatston—Score goes from 0 (a normal scan with no calcium at all) up to 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 for all-cause mortality, not just heart attack. 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. When grouped by increasing Calcium Scores, patients died at the following rates:

CAC score / mortality rate

• 0: 3%
• 1-10: 6%
• 11-99: 9%
• 100-399: 14%
• 400-999: 21%
• >1,000: 28%

Dr. Min explained, "In all asymptomatic patients, someone with a score of 0 has a minimal risk that they will die from any disease in the next 15 years. It's a very long-term warranty period.”

He added, “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. We have medicine that saves lives; we just need to identify earlier the right patients so that we can get them the right treatments."