New research helps clarify risk associated with high coronary artery calcium.
Having both severe left main coronary artery calcium and diabetes triples the risk of dying from cardiovascular disease in asymptomatic adults, research suggests.
The findings help clarify which patients would benefit from more intensive lipid-lowering therapies, experts say.
A US study including 2200 asymptomatic patients with no history of clinical atherosclerotic cardiovascular disease (ASCVD) or cardiovascular symptoms looked at results from coronary artery calcium scanning done because they had at least one ASCVD risk factor.
Participants were included if they had vessel-specific coronary artery calcium scores. Of those participants, 6% had a severe left main coronary artery calcium (LM CAC) score of 300 or above.
Over the 11-year follow up, researchers found that participants with a left main coronary artery calcium score of ≥300 had almost three times the risk of dying from coronary heart disease.
Participants with diabetes and a left main coronary artery calcium score of ≥300 had “exponentially higher [cardiovascular] mortality rates” of seven per 100 people, compared with 0.6 cardiovascular deaths per 100 people without diabetes or coronary artery calcium, the researchers said.
“Diabetes was the only traditional risk factor that was independently associated with ASCVD mortality and conferred a risk similar to that of a left main coronary artery calcium score of ≥100,” the researchers wrote in JACC: Cardiovascular Imaging.
“Most important, primary prevention patients with a CAC of ≥1,000 who had severe LM CAC (≥25% burden or a vessel-specific score of ≥300) and diabetes experienced a five-fold higher crude ASCVD mortality rate compared with ASCVD mortality rates previously reported for secondary prevention patients meeting guideline-defined very high-risk status.”
Participants with any CAC had a 12% increased risk of atherosclerotic cardiovascular disease mortality during the study.
Coronary calcium scoring was included in the Heart Foundation’s new cardiovascular risk calculator last year as one of five “reclassification factors” to improve risk estimates when a patient’s score was close to another risk threshold.
Professor Rajesh Puranik, consultant cardiologist at Sydney’s Royal Prince Alfred Hospital, said the research was helpful in providing evidence to patients about the importance of primary prevention.
“When you’re intermediate risk, the fact that you’re diabetic and you have left main calcification, you have a high calcium score, may help that intermediate group to understand why they should go on to cholesterol-lowering therapies earlier,” CSANZ’s clinical practice advisor told TMR.
“That will be the classic discussion point with a patient and doctor where the patient’s saying, ‘I’m a really healthy person, I know my cholesterol is a bit up, but I don’t want to treat it’.
“They may have a really strong family history. And then you find out that their calcium score is super elevated.
“You’re trying to talk them into having a statin drug that they don’t really want, and you’ve got to provide some evidence that their risk is higher than what they thought it was.
“The CT calcium score is further adding to the individualisation of our treatment and their risk stratification.”
Professor Puranik said calcium scoring indicated the biological age of a patient’s arteries.
“When it’s in that cohort of diabetics, and in this particular location of the left main artery, in those people they derive the greatest benefit [of treatment] because they have the greatest events,” he said.
But Professor Puranik said calcium scoring should not be used as a more widespread screening tool in the general population.
“There’s a temptation, especially from some GPs, to run the calcium score on everyone, but it doesn’t make sense to do that because of the issue of it being potentially falsely reassuring when it shouldn’t be,” he said.
“The most likely blockage to cause an acute heart attack is unlikely to be one with calcium. It’s more likely to be one with a cholesterol plaque, and that’s not seen in this imaging. Calcium plaques tend to be a bit more stable and the cholesterol-laden plaques are ones that are not seen and tend to be unstable.”
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Professor Puranik said the coronary calcium score helped further risk stratify patients who were close to high risk on the Heart Foundation’s risk calculator.
“If they end up closer to high, then you could be making stronger advice on cholesterol lowering drugs, blood pressure lowering drugs and getting your diabetes under control,” he said.
“We’re using it in a tailored fashion in the intermediate group to answer a specific question. We’re not doing it willy-nilly on the whole population. We certainly don’t need to do it in high risk because they’ll follow their own algorithm.
“Anybody with any kind of symptoms, they automatically pass go and must see a cardiologist. And we won’t do it in low-risk [patients] – we’ll just repeat their risk assessment again in a couple of years.”
A spokeswoman for the Heart Foundation said they were working with government and digital health agencies to embed the risk calculator into general practice software.
