Individuals who have no known heart disease can still have atherosclerotic changes, which can be detected  on routine screening, suggests a new study from Sweden, which found that more than 40% of adults aged 50-64 years, who had no known heart disease had some degree of atherosclerosis.^1,2

The multicenter study recruited 25,182 participants, aged 50 to 64 years, from the Swedish census register from 2013 to 2018 as part of the Swedish CArdioPulmonary BioImage Study (SCAPIS). Persons who had not suffered a myocardial infarction any time earlier nor had undergone a cardiac intervention were included in the study; women constituted 50.6% of the study population.

All the participants underwent coronary artery calcification (CAC) scans and coronary computed tomography angiography (CCTA) scans using dedicated dual-source CT scanners. Noncontrast images were scored for CAC. Coronary atherosclerosis per segment was scored and defined as no atherosclerosis, 1% to 49% stenosis or ≥50% stenosis.

Results published in the journal Circulation showed that 42.1% of the study participants had some atherosclerotic deposits in their blood vessels; and 5.2% of these individuals  had obstruction to  the blood flow through at least one coronary artery by ≥50%. In around 2% of cases, the atherosclerotic changes were severe enough to narrow the left main, proximal left anterior descending artery, or 3-vessel disease. A total of 2.4% had only noncalcified plaques on CCTA, while 8.3% had a mix of noncalcified and calcified plaques. The prevalence of noncalcified plaques was higher in men aged 60-64 years versus women in the same age group; 14.2% vs 7.0%, respectively while in the 50–54-year age group, it was  8.4% vs 3.7%, respectively.

Atherosclerosis developed at least a decade earlier in men than in women. Compared to the 50-54-year age group, those aged 60-64 years were 1.8 times more likely to have atherosclerotic deposits.

Participants with higher levels of atherosclerosis on CCTA also scored higher on CAC. All those who had a CAC score of > 400 had had atherosclerosis and substantial blockage amounting to 45.7%.

Interestingly, 5.5% of those with a CAC score of zero were found to have atherosclerosis detected by CCTA, and 0.4% of them had significant obstruction of blood flow. This subgroup of individuals was also more likely to have more risk factors; 6.8% were current smokers, 6.0% had a strong family history of heart attack and 8.1% had diabetes.

This study has shown that silent coronary atherosclerosis is a common finding in middle-aged individuals, even if they have not been diagnosed with heart disease. The prevalence increases with advancing age. This study has also demonstrated that CAC scoring to screen individuals at risk of heart disease can detect calcium-containing plaque in the coronary arteries, but it can still miss the non-calcified plaques. While high scores (≥400) are suggestive of significant blockage and a higher probability of suffering a heart attack, stroke or associated mortality within the next decade, a zero CAC score does not absolutely rule out atherosclerosis, as also corroborated by this study.

CAC score has been traditionally used as a marker for atherosclerosis. Though the incidence is small, relying solely on CAC scoring for stratifying risk can miss those at higher risk for heart attack despite a zero CAC score, particularly in those who also have other risk factors for heart disease at baseline. The “2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease” recommends a CAC score to assess ASCVD risk. However, the observations of this study support addition of CCTA imaging in risk assessment and may prevent future heart attacks.

References

1. Bergström G, et al. Prevalence of subclinical coronary artery atherosclerosis in the general population. Circulation. 2021 Sep 21;144(12):916-929.
2. AHA News, Sept. 20, 2021.