CAC Scores Better for Predicting Heart Attack than Stroke

This study was originally published on DiagnosticImaging.com

Parag Joshi, MD

A new study from investigators at the University of Texas Southwestern Medical Center is shedding new light on the clinical use of CT scans of calcified plaque for predicting 10-year heart attack and stroke risk.

Results of the study, which incorporated data from the Multi-Ethnic Study of Atherosclerosis and the Dallas Heart Study, indicate the coronary artery calcium (CAC) scores derived from the scans were better at predicting risk of heart attack than stroke.

“In our study, there was a two-fold greater risk of heart attack than stroke at CAC levels at or above 100,” said senior author Parag Joshi, MD, cardiologist and assistant professor of internal medicine. “That held true for black, white, and Hispanic men and women.”

These results, Joshi said, could help providers decide how aggressively to treat patients who have never have a major cardiac event, but who also have other risk factors, such as high blood pressure or high cholesterol.

The team’s findings were based on the evaluation of CT scans from 7,042 participants culled from the aforementioned studies. Based on those images, they divided the patients by the American Heart Association and American College of Cardiology’s calcium risk categories: 0, 1-99, and 100 and above. They also sub-divided the participants by sex and race in order to calculate the different risk levels.

Based on their analysis, the team found the risk for a heart attack was twice as high than a stroke for individuals with CAC scores greater than 100. For men in this group, the overall 10-year heart attack risk was 12 percent – slightly higher at 14 percent for Hispanic men – and it was 8 percent for women. Stroke risk in this group remained below 8 percent for all groups, but it was higher among women, black, and Hispanic participants.

For individuals in the 1-99 CAC score group, the risk for both heart attack and stroke hovered below 6 percent. But, women in this cohort had a greater stroke risk while men had a higher risk for heart attack. Among individuals with a 0 score, the 10-year risk for heart attack or stroke was less than 2 percent.

It is possible, Joshi’s team contended, that providers could use these findings from CT scans to inform their decisions about whether to place a patient on statin drugs when the choice is not clear-cut based on other factors, such as smoking history, blood pressure, or cholesterol.

“If you think your patient should be on a statin, and your patient does not want to take it, this can be a good arbitrator for that,” he said. “Our findings also highlight some of the nuance between heart attack risk and stroke risk and how our patients might consider those two risks in their decision making.”

This study is the first to compare the predictive value for heart attack and stroke risks. And, according to Leslee Shaw, PhD, professor of health services research in radiology in the Dalio Institute of Cardiovascular Imaging at Weill Cornell Medicine, the data is sufficiently robust to beneficial impact clinical care.

“The current report represents an important validation of prior prognostic results using CAC,” Shaw said in an accompanying editorial. “The comparison of coronary heart disease versus stroke risk based on CAC findings adds novelty to this report and represents important information to enhance clinical decision making regarding asymptomatic screening for atherosclerotic cardiovascular disease.”

This study, “Predictive Value of Coronary Artery Calcium Score Categories for Coronary Events Versus Strokes: Impact of Sex and Race,” was published in Circulation: Cardiovascular Imaging.