Higher CAC Burden Associated With Greater SCD Risk, Regardless of ASCVD Risk Factors

A higher burden of coronary artery calcium (CAC) may be associated with a higher risk of sudden cardiac death (SCD), regardless of the presence of risk factors for atherosclerotic cardiovascular disease (ASCVD), according to a study published in JACC: Cardiovascular Imaging and being presented April 2 at ACC.22.

Alexander C. Razavi, MD, MPH, PhD, et al., used data from CAC Consortium, a multicenter observational cohort of patients without known coronary heart disease (CHD) who underwent CAC testing, to assess the association between CAC burden and SCD among patients without clinical ASCVD. The researchers also looked at whether age and sex affected the relationship between CAC and future SCD.

The study included all 66,636 CAC Consortium participants who were referred for CAC scanning from 1991 to 2010 because of underlying ASCVD risk factors and uncertainty of long-term ASCVD risk. CAC scanning was obtained using noncontract, ECG-gated cardiac CT. Participants were categorized into five score groups: CAC of 0; CAC of 1-99; CAC of 100-399; CAC of 400-999; and CAC >1,000. SCD events were considered when an SCD ICD code was listed as the underlying cause of death on the participant's death certificate or if an SCD ICD code was listed as the primary cause of death, with CHD as the secondary cause. 

Participants had an average of 54.5 years, 33% were women and 11% were non-White. More than half of the participants (55.3%) had a CAC score >0, and 55% had a 10-year ASCVD risk of less than 5%. Over a median follow-up of 10.6 years, there were 211 SCD deaths, 91% of which occurred in patients with CAC >0. SDC rates were more than twofold higher among patients with CAC scores of 1-99 (0.13 per 1,000 person-years) vs. those with CAC scores of 0 (0.05 per 1,000 person years). The difference was greater for those with CAC scores of 100-399 (0.48 per 1,000 person years); 400-999 (0.94 per 1,000 person years); and >1,000 (1.85 per 1,000 person years).

The 10-year risk of ASCVD at baseline did not significantly change the association between CAC and SCD, although CAC scores 400-999 and >1,000 were "nominally more strongly associated" with SCD in those with <7.5% ASCVD risk vs. those with an ASCVD risk >20%. The SCD risk within each CAC burden category and the association between CAC and SCD were similar for men and women.

According to the researchers, the findings demonstrate that quantifying CAC burden early in primary prevention patients can help refine SCD risk early. They add that the findings "suggest that SCD risk stratification may be most useful in the very early stages of CHD through the quantification of calcified atherosclerotic plaque burden." Future research looking at the role of CAC scoring to support additional testing "may be useful to help further guide primary prevention strategies for SCD risk assessment," they conclude.

Clinical Topics: Arrhythmias and Clinical EP, Noninvasive Imaging, Prevention, Atherosclerotic Disease (CAD/PAD), SCD/Ventricular Arrhythmias, Computed Tomography, Nuclear Imaging

Keywords: ACC22, ACC Annual Scientific Session, Calcium, Cardiovascular Diseases, Follow-Up Studies, International Classification of Diseases, Plaque, Atherosclerotic, Risk Assessment, Risk Factors, Primary Prevention, Tomography, X-Ray Computed, Death, Sudden, Cardiac, Electrocardiography, Vascular Calcification, Coronary Artery Disease

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