Coronary Calcium Helps Stratify 10-Year Cardiac Risk in Diabetes

Marlene Busko

November 24, 2017

IRVINE, CA — Coronary artery calcium (CAC) scores may be better at predicting the risk of a cardiovascular disease (CVD) event in patients with type 2 diabetes than traditional scores such as Framingham, even in those who've had diabetes for 10 years, researchers report[1].

This conclusion is based on a new analysis of participants in the Multi-Ethnic Study of Atherosclerosis (MESA) published online in JAMA Cardiology by Dr Shaista Malik (University of California, Irvine) and colleagues.

"When we consider how we want to treat a person with type 2 diabetes, how aggressive to be, most of the guidelines . .  . consider having type 2 diabetes to be equivalent to having already had a heart attack," Dr Malik told | Medscape Cardiology.

However, the new findings indicate that people with diabetes or metabolic syndrome "are a rather heterogeneous group," she stressed.

They suggest that "diabetes in particular may not be a coronary artery disease equivalent, and we should see whether a patient could benefit from additional screening such as a coronary calcium score to improve personalization of therapy."  

Asked for his thoughts, Dr Donald W Bowden (Wake Forest School of Medicine, Winston-Salem, NC), who was not involved in the study, told | Medscape Cardiology that these new data add "to an extensive literature documenting the utility of CAC imaging to improve prediction and aid treatment of CVD in both people with and without diabetes."

"It shows that inferences from shorter-term follow-up studies remain compelling over long periods," he said in an email.    

Moreover, this also demonstrates that "CAC reclassifies a significant percentage of [diabetes] patients," he noted, pointing out that when CAC scores were compared with the Framingham risk or other scores, almost half the patients with diabetes were reclassified to a higher or lower CVD risk group.

Malik said that for patients with diabetes "the general thinking has been . . . they probably are going to have coronary calcium, so further risk stratification is not going to be more predictive. But what we're showing is—even in those with diabetes—getting information on how calcified their coronary arteries are is helpful in distinguishing those at lower risk from those at higher risk."

Low CAC Score Can Be Considered "Warranty" for 10 Years in Diabetes

Malik and colleagues examined data from the MESA cohort of 6814 men and women aged 45 to 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 US communities from July 2000 through August 2002.

The patients had a cardiac-gated electron-beam multidetector CT scan to determine CAC, and they were divided into four groups based on CAC scores from low to high: 0, 1–99, 100–399, and ≥400.

A total of 6751 participants with complete data were included in the current analysis. They had a mean age of 62 years and 47% were male.

Diabetes was defined as a fasting serum glucose ≥126 mg/dL. 

Metabolic syndrome was defined as having at least three of the following five conditions: waist circumference ≥102 cm in men or ≥88 cm in women; triglycerides ≥150 mg/dL; HDL cholesterol <40 mg/dL in men or <50 mg/dL in women; blood pressure ≥130/85 mm Hg or use of antihypertensive medication; and fasting serum glucose 100–126 mg/dL. 

At baseline, 13.0% of participants had diabetes, 26% had metabolic syndrome, and 61% had neither.

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 1738 participants with metabolic syndrome, there were 115 CHD events and 175 atherosclerotic CVD events.

The 4132 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 adjustment 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.

More Study Needed to Understand Resilience, Guide Individualized Care

"Although diabetes is known to accelerate the aging process, future studies need to focus on the factors that provide resilience among patients with lack of subclinical disease despite long-standing diabetes," say Malik and colleagues.

"Maybe we do need to be aggressive in hyperglycemia management or less aggressive in lipid management," and further research may show that clinicians don't need to put all patients with diabetes on a high-intensity statin; rather "they could get away with a moderate-intensity statin," Malik suggested.

In addition, more work is needed to "examine whether newer antidiabetic medications, such as sodium glucose cotransporter 2 inhibitors or glucagonlike peptide 1 receptor agonists, that benefit patients with known [atherosclerotic CVD] could be considered for those at increased risk based on extent of CAC or other measures of subclinical atherosclerosis," the group writes.

"Prospective studies that focus treatment intensity on objective measures of subclinical atherosclerosis may improve personalization of preventive therapies."

The authors have reported no relevant financial disclosures.

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