Vascular disease

Silent atherosclerosis missed by CAC scores, CCTA study shows

Subclinical coronary atherosclerosis is present in 40% of adults without established coronary disease and is not always predicted accurately by coronary artery calcification scoring, a large study using computed tomography angiography has shown.

The Swedish Cardiopulmonary Bioimage Study (SCAPIS) of 25,182 50–64 year olds without known heart disease found that 42.1% had CCTA- detected atherosclerosis and 5.2% had significant stenosis (≥50%). More severe atherosclerosis such as left main, proximal left anterior descending artery, or three-vessel disease was found in 1.9% of patients, the authors wrote in Circulation.

The prevalence of atherosclerosis was twice as high in men than women, in whom disease progression was similar but delayed by 10 years. As expected, CCTA showed that atherosclerosis increased with age and with the number of cardiovascular risk factors.

CCTA-detected atherosclerosis prevalence increased with increasing coronary artery calcification (CAC) score, but the study showed that CAC failed to detect significant atherosclerosis in some people.

Of those with 0 CAC scores, 5.5% had atherosclerosis and 0.4% had significant stenosis. Further, 9.2% of participants with 0 CAC and intermediate 10-year risk of atherosclerotic cardiovascular disease had CCTA-verified atherosclerosis.

All participants with a high CAC score (>400) had atherosclerosis and 45.7% had significant stenosis.

The study investigators said CCTA could potentially be an important atherosclerosis detection strategy to target preventive therapies, given that coronary risk assessment based on probabilistic risk scores is imprecise at the individual level and may overestimate or underestimate risk particularly for some subpopulations.

It could also complement CAC imaging, which the study had shown may miss or misdiagnose some atherosclerosis.

“This was mainly seen in participants with ultra-low CAC score (1 to 10) and could be explained by difficulties in assessing such low CAC scores with high reproducibility and the well-known difficulties in identifying small calcifications in the presence of iodinated contrast media,” the authors wrote.

In May 2021, the National Heart Foundation of Australia recommended that cardiologists could downgrade patients’ risk based on a 0 CAC score, though it “does not rule out the presence of non calcified plaque” and that they should “apply caution in underestimating the risk in the presence of certain risk‐enhancing factors (eg, Aboriginal and Torres Strait Islander population, cigarette smoking, diabetes, and a family history of cardiovascular disease)”.

“Subsequent risk management strategies should follow contemporary guidelines for absolute cardiovascular disease risk” and CAC can be reasonably retested at 5 years, “based on available evidence for conversion to positive CAC scores”.

An accompanying editorial said significant expansion of CCTA capacity would be needed to allow widespread risk assessment.

Randomised controlled trials are also be needed to determine whether CCTA-directed preventative therapies are superior to current risk-estimating practices, they added, noting that SCOT-HEART 2 trial is currently looking at CCTA’s efficacy in reducing the rate of fatal or nonfatal myocardial infarction versus risk scoring.

The authors said CCTA-detected atherosclerosis showed a good correlation with risk categories obtained using a screening questionnaire, with participants classified as high risk having up to a 2.9-fold higher prevalence of coronary atherosclerosis than those those classified as low risk.

However, as many as one in three men and one in four women rated as low risk by these equations were found to have coronary atherosclerosis.

“In this context, the SCAPIS investigators should explore the potential for novel blood and imaging biomarkers to identify those persons who are most likely to have subclinical coronary atherosclerosis,” they suggested.

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