CAC Scoring Helps Determine Net Benefit or Harm of Aspirin in Primary Prevention

October 30, 2020
Patrick Campbell

An analysis of the Dallas Heart Study from UTSW details how use of CAC scoring can help determine what patients would stand to benefit from aspirin use for primary prevention.

This story first appeared on Diagnostic Imaging's sister site Practical Cardiology.

In patients who are at risk for a heart attack or stroke, coronary artery calcium (CAC) scoring could help providers identify patients who could benefit the most from using aspirin as a primary intervention.

A new study from a team of investigators from the Preventive Cardiology Program at the University of Texas Southwestern outlines this potential new use for CAC scoring. The team, led by Amit Khera, M.D., professor of internal medicine and director of the Preventive Cardiology Program, used data from the Dallas Heart Study.

“Aspirin use is not a one-size-fits-all therapy,” Khera said in a statement. “CAC scanning can be a valuable tool to help us tailor care to help more patients avoid a first heart attack or stroke.”

Related Content: CT Scans for Arterial Plaque Better Predictor for Heart Attack Than Stroke

With guideline changes altering the use of aspirin in prevention settings, a new emphasis has been placed on predictors and factors associated with increased bleeding when used for primary prevention. In recent years, a multitude of studies have concluded CAC scoring was useful for identifying patients at an increased atherosclerotic cardiovascular disease (ASCVD) risk. With this in mind, Khera and colleagues designed the current study to examine whether CAC scoring could help determine the net estimated effect of aspirin at different risk thresholds.

Using the 6,101-patient Dallas Heart Study as a data source, investigators performed a search of patients free from ASCVD and not taking aspirin at baseline. From this search, investigators identified a cohort of 2,191 patients for inclusion in the current study. This cohort had a mean age of 44 (SD, 9.1) years, 57 percent were women, and 47 percent were Black.

Of note, all patients in the Dallas Heart Study were invited to three sequential visits to collect health information, including various imaging studies and electron beam computed tomography for CAC scoring. Of the 2,191 patients included in the study, 1,063 had a CAC of 0, 967 had a score of 1-99, and 161 had a score of 100 or greater.

The primary outcomes of the study were first bleeding event and first ASCVD event associated with hospitalization or death. Bleeding events were identified through the use of ICD-9 codes and the ASCVD outcome was defined as a composite of nonfatal myocardial infarction, coronary heart disease death, and nonfatal and fatal stroke.

Over a follow-up period lasting a mean of 12.2 (1.9) years, 116 first major bleeding events and 123 ASCVD events were observed. When assessing types of bleeding events, investigators found 81 (70 percent) were gastrointestinal and 18 were intracerebral. Investigators pointed out 24 (21 percent) of the 116 events were fatal bleeds.

Upon analysis, results indicated those with a CAC score of 1-99 were at a greater risk for ASCVD (HR, 4.8; 95 percent CI, 2.8-8.2; P <.01) and bleeding events (HR, 1.6; 95 percent C I, 1.1-2.4; P=.02) when compared to their counterparts with a score of 0. Results indicated those with a CAC score of 100 or greater were also at an increased risk of ASCVD (HR, 5.3; 95 percent CI, 3.6-7.9; P <.01) and bleeding events (HR, 2.6; 95 percent CI< 1.5-4.3; P <.01) when compared to those with a score of 0. However, investigators pointed out these association between bleeding events and CAC was attenuated in multivariable-adjusted models.

Using meta-analysis estimates for the effects of aspirin, irrespective of CAC, investigators found aspirin use was estimated to result in net harm for individuals at low and intermediate (less than 5 percent) 10-year ASCVD risk. For those considered to be at high-risk (20 percent or greater), aspirin use was associated with a net benefit.

When assessing bleeding risk, results suggested a CAC score of 100 or greater in patients considered to be at low bleeding risk indicated net benefit from aspirin use, but only in those at borderline or higher (5 percent or greater) 10-year ASCVD risk. Among individuals at higher bleeding risk, aspirin use was associated with net harm regardless of CAC and ASCVD risk.

In a related editorial, Miguel Cainzos-Achirica, MD, MPH, PhD, and Philip Greenland, MD, applaud investigators of the current study for adding to a growing body of evidence suggesting CAC scores could help guide aspirin use for primary prevention, but cautions that more conclusive studies are needed before overinterpreting data.

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“Until further studies become available, the overall consistent observations from the DHS and the MESA have important clinical implications…Although it has been proposed that clinical risk scores could aid in the identification of optimal candidates for aspirin therapy, CAC scores seem to be a better tool to inform risk management discussions involving aspirin, leading to a safer allocation in candidates who are appropriate and motivated—particularly in middle-aged populations,” wrote the pair.

This study, “Value of Coronary Artery Calcium Scanning in Association With the Net Benefit of Aspirin in Primary Prevention of Atherosclerotic Cardiovascular Disease,” was published in JAMA Cardiology.