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Mortality within 15 years appears unlikely with CAC score of zero
The annual mortality rate among low- and intermediate-risk adults with a coronary artery calcium score of 0 remained below 1% for nearly 15 years in a recent study.
Researchers assessed the long-term impact of a coronary artery calcium (CAC) score of 0 for the estimation of vascular age vs. chronologic age; compared the prognosis of a CAC score of 0 with other clinical prediction models; and quantified the "warranty period" for a CAC score of 0. The warranty period was defined as the time during which an individual remained in the low-risk category (annual mortality rate below 1%).
They analyzed 9,715 adults without known CAD undergoing CAC imaging (mean age, 53.4 years; 59.3% men). Participants were stratified by age, Framingham Risk Score (FRS) and Adult Treatment Panel III (ATP III) category. Mean follow-up was 14.6 years.
Valentina Valenti, MD, and colleagues used Cox regression to assess all-cause mortality, area under the receiver operating characteristic curve (AUC) to determine the discriminatory power of CAC score over FRS and ATP III category. They also evaluated whether the addition of CAC score to FRS and ATP III would result in reclassification.
CAC score predicted mortality
Valenti, from the Dalio Institute of Cardiovascular Imaging, NewYork-Presbyterian Hospital and Weill Cornell Medical College, and colleagues found that 4.7% of the 4,864 adults with a CAC score of 0 at baseline died during follow-up vs. 14.6% of 4,851 who had a CAC score greater than 0 (P < .001).
Results from multivariable analyses indicated that a CAC score greater than 0 was the strongest predictor of death beyond individual CV risk factors, FRS and ATP III category (HR = 2.67; 95% CI, 2.29-3.11). The researchers found that the addition of CAC improved discrimination compared with FRS (AUC, 0.71 vs. 0.64; P < .001) or ATP III category alone (AUC, 0.72 vs. 0.64; P < .001). Risk classification for incident mortality also improved, as did reclassification of events and nonevents, compared with FRS or ATP III category alone (P < .001 for all).
Risk for mortality was increased with a higher CAC score, independent of FRS and ATP III category, and was consistent between men and women, according to the researchers.
Warranty period
A CAC score of 0 was associated with a nearly 15-year warranty period, during which the observed rate of mortality was less than 1%.
The warranty period of those with a CAC score of 0 but at high CV risk was only 5 to 6 years, but that was longer than for those with a CAC score greater than 0 but at low or intermediate risk, Valenti and colleagues wrote.
They also found that a CAC score of 0 was associated with vascular age below chronologic age as follows: 1 year for adults aged 50 to 59 years, 10 years for those aged 60 to 69 years, 20 years for those aged 70 to 79 years, and 30 years for those aged at least 80 years.
“Taken together, these findings indicate the robustness of a CAC = 0 to identify individuals disposed to a particularly propitious outcome, and may be useful as an adjunct measure to everyday clinical risk assessment,” Valenti and colleagues wrote. – by Erik Swain
Disclosure: Valenti reports no relevant financial disclosures. Two other researchers report financial ties with Arineta, AstraZeneca, Bristol-Myers Squibb, GE Healthcare, HeartFlow, Phillips Healthcare, St. Jude Medical and Vital Images.