CAC percentile stability may have implications for CV risk communication

BOCA RATON, Fla. — A significant proportion of individuals with a coronary artery calcium score greater than the 75th percentile based on age and sex do not qualify for statin treatment according to absolute coronary artery calcium score or 10-year atherosclerotic CVD risk score alone, according to data reported at the American Society for Preventive Cardiology’s Congress on Atherosclerotic Cardiovascular Disease Prevention.

American College of Cardiology and American Heart Association guidelines published in 2013 recommend statin treatment in individuals with clinical atherosclerotic CVD (ASCVD), LDL ≥ 190 mg/dL, diabetes and ASCVD risk score ≥ 7.5%. “However, in selected individuals for whom a decision to initiate statin therapy is unclear, additional risk factors may be considered, including coronary artery calcium (CAC) score ≥ 300 Agatston Units or CAC score ≥ 75th age- and sex-specific percentile,” Anurag Mehta, MD, from the department of internal medicine at UT Southwestern Medical Center, said during a presentation.

The researchers sought to characterize the overlap of coronary artery calcium (CAC) scores ≥ 75th percentile, absolute CAC scores and 10-year ASCVD scores risk, as well as describe the stability of CAC ≥ 75th percentile over time.

The study was a first-place winner in the Young Investigator Awards announced during the congress. Mehta presented the data on behalf of Micah T. Eades, MD, from the department of internal medicine at UT Southwestern Medical Center.

The study population included participants of the multiethnic, population-cohort Dallas Heart Study (phase 1: 2000-2002; phase 2: 2007-2009). The researchers used a reference population of 968 participants of the Dallas Heart Study phase 2 and their spouses to defined CAC percentiles; this excluded individuals with CVD and end-stage renal disease. The CAC percentiles were then applied to 699 participants (men aged 45 years and older; women aged 50 years and older) who had paired CAC scans performed during the Dallas Heart Study phases 1 and 2 nearly 7 years apart. The 2013 ACC/AHA Pooled Cohort ASCVD Risk Equation was used to determine 10-year ASCVD risk.

The researchers obtained 50th, 75th and 90th CAC percentiles for men and women. Among women aged 50 to 54 years, the median CAC score was 0 in the 50th percentile, 11 in the 75th percentile and 111 in the 90th percentile. Among men aged 45 to 49 years, the median CAC score was 0 in the 50th percentile, 8 in the 75th percentile and 107 in the 90th percentile. “CAC scores increased for all three percentile categories as age increased,” Mehta said.

At baseline, women with CAC ≥ 75th percentile had higher absolute CAC scores, BMI, total cholesterol and 10-year ASCVD risk, and were more likely to have hypertension and smoking status. Men with CAC ≥ 75th percentile also had higher absolute CAC scores, BMI and 10-year ASCVD risk, and were more likely to have diabetes and hypertension.

The researchers examined distribution of CAC ≥ 75th percentile by 10-year ASCVD risk and by absolute CAC score. Sixty percent had 10-year ASCVD risk < 7.5% and 76% had an absolute CAC score < 300, both of which are thresholds for statin initiation, according to the researchers.

After a median of 6.7 years of follow-up, CAC remained ≥ 75th percentile for 76% of participants. However, a higher percent of participants’ CAC scores remained ≥ 90th percentile. More than 80% of individuals remained at their initial percentile or higher when the researchers used continuous percentiles instead of categorical percentiles, according to the results presented.

The researchers also evaluated participants with CAC ≥ 75th percentile on the initial scan during phase 1 of the Dallas Heart Study who decreased their category to < 75th percentile on the follow-up scan. These individuals were younger, had lower absolute CAC scores and 10-year ASCVD risk and were less likely to have hypertension and diabetes compared with those who stayed at or above the 75th percentile, Mehta said.

“CAC ≥ 75th percentile and other risk measures are not synonymous. There is a need for clarity in the guidelines,” the researchers concluded. “Stability of CAC percentiles may have implications for longer-term risk communication.”

Reference:

Eades MT, et al. Abstract 113. Presented at: American Society for Preventive Cardiology Congress on Atherosclerotic Cardiovascular Disease Prevention; Sept. 16-18, 2016; Boca Raton, Fla.

Disclosure: Cardiology Today could not confirm relevant financial disclosures.