Radiology: CAC score can help predict future function in elderly population

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Coronary calcium is visible as white spots. Image source: Annals of Rheumatic Diseases
Coronary artery calcium (CAC) scores correlated with future regional wall motion abnormalities in an elderly cohort, according to a study published in the October issue of Radiology.

Cardiologists can use CAC scores to help predict risk of coronary artery disease obtained by the Framingham risk score; however, data exploring the relationship between CAC and cardiac function are limited.

Researchers, led by Patrick M. Colletti, MD, of the department of radiology and preventive medicine at University of Southern California in Los Angeles, hypothesized that “subclinical atherosclerosis as measured by using CAC scores will correlate with future left ventricular ejection fraction (LVEF) reduction and visible regional wall motion abnormalities (RWMA).”

Colletti and colleagues evaluated the hypothesis over an 11-year follow-up by recruiting 386 of the 1,461 South Bay Heart Watch (SBGW) participants to undergo functional analysis by cardiac MR imaging from May 2005 to November 2006. The cohort (mean age, 75.2 years) had undergone CT between 1993 and 1994 to determine CAC.

Colletti and colleagues processed cardiac MR data and identified 160 regions of interest to determine end-diastolic volume (in milliliters), end-systolic volume (in milliliters) and LVEF (as a percentage). Investigators used consensus to determine wall motion and correlated RWMA with the most likely culprit coronary vessel, according to Colletti and colleagues.

Baseline CAC scores were segregated into four categories: a score of zero, scores of 1 to 99, scores of 100 to 399 and scores of 400 and greater. The researchers compared myocardial function parameters using an analysis of variance for LVEF, diastolic peak filling rate (PFR) and wall motion score and X2 tests for discrete MRI variables, according to the authors.

Higher CAC scores were associated with slightly lower LVEF and a greater percentage of participants with decreased PFR and RWMA, according to the researchers. However, after controlling for age and risk factors, only RWMA was associated with higher CAC, reported Colletti and colleagues. The researchers also found that CAC scores of 100 or more were associated with a 2.2-fold increase in RWMA.

“The greater prevalence of RWMAs associated with higher baseline levels of CAC demonstrated in this study may have clinical relevance,” wrote Colletti.

The authors acknowledged several limitations to the study. Participants in the MR imaging subset were younger than nonparticipants from the original SBHW, and original participants with higher baseline CAC scores were less available for the cardiac MR study. The MR cohort had a lower prevalence of elevated CAC scores than might be expected, according to Colletti.

Although researchers could not determine whether MR-detected abnormalities were present at the original CAC score, they concluded that subclinical atherosclerosis demonstrated by CAC score correlates with future RWMAs.