Coronary artery calcium (CAC) scores better at predicting risk of cardiovascular disease (CVD) event in patients with type 2 than traditional scores.
This result is based on a new published study, Multi-Ethnic Study of Atherosclerosis (MESA). Coronary arterial calcification is part of the development of atherosclerosis, occurring almost exclusively in atherosclerotic arteries being absent in normal vessel walls. Atherosclerotic plaque proceeds through progressive stages where instability and rupture can be followed by calcification, providing stability to an unstable lesion. Coronary artery calcium score (CAC) is determined by electron-beam (EBCT) and multi-detector (MDCT) computed tomography. It has a strong correlation with the total coronary atherosclerotic burden and is able to define CHD risk, being an independent predictor of cardiovascular disease.
A coronary calcium scan is painless and noninvasive and takes less than 10 minutes. It uses a rapid computed tomography (CT) imaging system that is at least 20 times faster than a normal CT scan. During the test, you lie face up on an examination table while X-rays are passed through your body. Calcium in the artery walls appear as whitish spots or streaks on the X-rays. A computer program is then used to calculate a calcium score that reflects the total calcium buildup in the coronary arteries. The American Heart Association considers coronary calcium scanning a reasonable option for people who have no symptoms of coronary heart disease but are at intermediate risk for the disease and are uncertain about whether to go on a statin and/or aspirin.
Coronary calcium scanning is a way to evaluate the health of the coronary arteries. Also known as electron-beam computed tomography, coronary calcium scans measure the amount of calcium in the coronary arteries. Calcium is often a component of plaques and is not present in healthy arteries. In a middle-aged or older individual, about one-quarter of the area of an atherosclerotic plaque is calcified. Scores of 1 to 10 indicate arteries with very mild buildup of calcium-containing plaque; scores of 11 to 100 signify mild buildup of this type of plaque; and scores of 101 to 400 indicate moderate calcium-containing plaque formation. People with higher calcium scores have a greater risk of heart attack and stroke over the next decade than those with lower scores.
The researchers examined data from the MESA cohort of 6,814 men and women ages 45–84 years without known CVD. Participants were ethnically diverse—White (38.5%), African American (27.5%), Hispanic (22%), and Chinese (12%)—and were enrolled in six U.S. communities from July 2000 through August 2002. The patients were divided into four groups based on CAC scores from low to high: 0, 1–99, 100–399, and ≥400. A total of 6,751 participants with complete data were included in the current analysis. They had a mean age of 62 years and 47% were male.
The primary end-point was an incident CHD event (myocardial infarction, resuscitated cardiac arrest, or coronary heart disease [CHD] death). The secondary end-point was an incident atherosclerotic CVD event (CHD event and fatal or nonfatal stroke). During a mean follow-up of 11 years, among the 881 participants with diabetes, there were 84 incident CHD events and 135 atherosclerotic CVD events. Among the 1,738 participants with metabolic syndrome, there were 115 CHD events and 175 atherosclerotic CVD events. The 4,132 participants with neither condition had relatively fewer CHD (157) and atherosclerotic CVD events (250). More than a third (37%) of patients with diabetes, 45% of those with metabolic syndrome, and 55% of the other patients had a baseline CAC score of 0, and this was associated with a low 10-year risk of CHD events.
Among patients without evidence of CAC at baseline, the 10-year CHD event rates were just 2.3% in patients with metabolic syndrome and 3.7% in patients with diabetes. And this was independent of diabetes duration, insulin use, or glycemic control, even after adjusting for multiple confounders. “Thus, the ‘warranty period’ of a CAC score of 0 can be extended to 10 years in those with metabolic syndrome or diabetes,” according to the researchers.
- The findings add to evidence that calcium scores can give a clearer picture of a person’s future heart attack and stroke risk.
- People with coronary calcium scores of 100 or higher had a two- to threefold higher risk, versus those with no calcium buildup in their arteries.
- Using the calcium score for people with a family history of early heart disease can help to prevent a heart attack with proper treatment.
Malik S, Zhao Y, Budoff M, et al. Coronary artery calcium score for long-term risk classification in individuals with type 2 diabetes and metabolic syndrome from the Multi-Ethnic Study of Atherosclerosis. JAMA Cardiol 2017; DOI:10.1001/jamacardio.2017.4191. Abstract