The benefits of aspirin therapy for primary prevention of cardiovascular disease outweigh the risks in patients who have coronary artery calcification scores of 100 or more, while the opposite is true in those who have scores of 0, according to a subanalysis of the MESA study published online May 6 in Circulation: Cardiovascular Quality and Outcomes.
In addition, the coronary artery calcium (CAC) score, a highly specific marker of the atherosclerotic plaque burden in the coronary arteries that is obtained via chest CT, predicts the risk/benefit ratio of aspirin therapy independently of traditional risk factors. These findings indicate that it can be used to guide aspirin therapy regardless of whether patients "qualify" for it according to AHA guidelines, said Dr. Michael D. Miedema of the Minneapolis Heart Institute and his associates.
Dr. Michael Miedema
At present, aspirin therapy for primary prevention is recommended only for patients at elevated risk for a cardiovascular event because its risks, particularly that of bleeding, are considered to outweigh the benefits. This means aspirin prevention is withheld from lower-risk patients "who represent the majority of the primary prevention population and in whom a large proportion of CVD events occur."
Dr. Miedema and his colleagues assessed whether CAC could be used to fine-tune risk assessment and thus allow treatment of more patients, preventing more cardiovascular events while avoiding unnecessary exposure of patients in whom risk truly exceeds benefit.
They analyzed data from the Multi-Ethnic Study of Atherosclerosis, a longitudinal epidemiologic study involving 6,814 men and women aged 45-84 years at baseline in 2000 who were followed at six U.S. medical centers for a median of 7.6 years.
For their study, Dr. Miedema and his associates included 4,229 of these individuals in whom CAC scores were obtained at enrollment, none of whom had clinical CVD or diabetes at that time. A total of 56% had a CAC score of 0, 18% had a CAC score of 100 or more, and the remaining 26% had intermediate CAC scores of 1-99.
Compared with patients who had a CAC score of 0, those with CAC scores of 100 or higher had more than a ninefold higher risk (hazard ratio, 9.03) for a coronary heart disease event, defined as nonfatal MI, resuscitated cardiac arrest, or CHD death; and more than a sixfold higher risk (HR, 6.57) for a CVD event, defined as a CHD event or stroke, during follow-up. This difference remained robust after the data were adjusted to account for traditional risk factors, in both men and women, and regardless of patient age (Circ. Cardiovasc. Qual. Outcomes 2014 May 6 [doi:10.1161/circoutcomes.113.000690]).
The findings indicate that CAC score can be used to guide aspirin therapy, at least in the 74% of patients whose scores fall at the extreme ends of the spectrum rather than in the intermediate range, the researchers noted.
This study was supported by the National Heart, Lung, and Blood Institute and the National Center for Research Resources. Dr. Miedema and his associates reported no financial conflicts of interest.