Ischaemic heart disease

Research questions benefit of coronary artery calcium scans

Coronary artery calcium (CAC) scans provide only a “modest gain” in the risk assessment of cardiovascular disease that could be outweighed by the costs, an Australian review and meta-analysis has found.

The research, published in JAMA Internal Medicine, found the use of CAC scores to determine high-risk patients had the potential to cause harm through inappropriate diagnostic labelling, unnecessary treatment and testing.

But a leading Australian cardiologist has defended the precision of CAC scans for cardiovascular disease risk assessments, saying a population-level approach cannot provide the individual assessment generated by the scans.

The review assessed cardiovascular disease event outcomes from 2272 international studies, finding just six eligible cohort studies that evaluated the risk of actual cardiovascular events after adding a CAC score to the cardiovascular risk, compared to the cardiovascular risk without the CAC analysis.

“Despite variation in the overall risk of the study populations (event rates ranging from 0.9% to 9.4%), the improved discrimination was relatively consistent,” the research paper found.

“The mean discrimination gain of 0.036 is modest, but many in important in some subgroups, and adjusted hazard ratios suggest the test may have incremental prognostic value for some participants.

“However, 85.5% to 96.4% of participants reclassified as being at intermediate or high risk by CACS did not have a CVD event during follow-up.”

The patients were from the community or out-patients without current cardiovascular disease.

Research author Associate Professor Katy Bell told the limbic the potential benefits of CAC scans above traditional risk factor analysis “appears to be small”, citing the study’s finding that fewer 4% to 15% of patients reclassified as higher risk by the scans had a cardiovascular event during their follow up period. This timeframe ranged from just over five years to 10 years.

“There is currently no direct evidence that adding CAC score information to traditional risk factors provides clinical benefit,” she said. “These small and uncertain benefits may often be outweighed by harms.”

Associate Professor Bell said the potential harms included a “cascade of unnecessary tests, diagnoses, and treatments”, risks of radiation exposure, significant financial and opportunity costs to patients, and carbon emissions from the scans.

She said their findings were largely consistent with the CSANZ position on CAC scans recommendations for low- and high-risk patients, noting the research concluded CAC scans could be beneficial for determining risk to justify medication.

“However, exactly which patients may benefit from having a scan is currently unclear,” she said.

“Our study found evidence that CAC scans may provide modest, but potentially useful, prognostic information beyond traditional risk factor assessment and CVD risk calculation. This suggests that they may be beneficial for some selected patients where the result would change clinical decisions about preventative treatment.”

However, cardiologist Professor Hamilton-Craig, who was a co-author of the Cardiac Society of Australia and New Zealand’s Coronary Artery Calcium Scoring Position Statement, said the use of CAC scanning remained an appropriate tool for personalised care.

“The problem with epidemiology is that it seeks to understand – through use of population-level data – how various treatments may affect outcomes in the general population,” he said.

“In an individual the question that clinically arises is what is this individual’s risk of cardiovascular events, and population data does not answer that question for the individual. That is a lack of precision.

“Does this individual in front of me have sub-clinical coronary atherosclerosis that we didn’t know about, and coronary calcium scoring is the answer to that, although CT-angiography may add some nuance.”

He compared the use of CAC scans at population level to a mammogram of the heart

Professor Hamilton-Craig said high-risk individuals should be treated without CAC scoring, but there was a role for CAC scan precision-medicine to determine treatment for low-risk and intermediate-risk patients.

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