Study objective: We seek to determine whether cardiac risk factor burden (defined as the number of conventional cardiac risk factors present) is useful for the diagnosis of acute coronary syndromes in the emergency department (ED) setting.
Methods: This was a post hoc analysis of the Internet Tracking Registry of Acute Coronary Syndromes (i*trACS) registry, which had 17,713 ED visits for suspected acute coronary syndromes. First visit for US patients who were not cocaine or amphetamine users, who did not leave against medical advice, and for whom ECG and demographic data were complete were included. Acute coronary syndrome was defined by 30-day revascularization, diagnostic-related group codes, or death within 30 days, with positive cardiac biomarkers at index hospitalization. Cardiac risk factors were diabetes, hypertension, smoking, hypercholesterolemia, and family history of coronary artery disease. Cardiac risk factor burden was defined as the number of risk factors present. Because multiple logistic regression analysis revealed that age modified the relationship between cardiac risk factor burden and acute coronary syndromes, a stratified analysis was performed for 3 age categories: younger than 40, 40 to 65, and older than 65 years. Positive likelihood ratios and negative likelihood ratios with their 95% confidence intervals (CIs) were calculated for each total risk factor cutoff.
Results: Of 10,806 eligible patients, 871 (8.1%) had acute coronary syndromes. In patients younger than 40 years, having no risk factors had a negative likelihood ratio of 0.17 (95% CI 0.04 to 0.66), and having 4 or more risk factors had a positive likelihood ratio of 7.39 (95% CI 3.09 to 17.67). In patients between 40 and 65 years of age, having no risk factors had a negative likelihood ratio of 0.53 (95% CI 0.40 to 0.71), and having 4 or more risk factors had a positive likelihood ratio of 2.13 (95% CI 1.66 to 2.73). In patients older than 65 years, having no risk factors had a negative likelihood ratio of 0.96 (95% CI 0.74 to 1.23), and having 4 or more risk factors had a positive likelihood ratio of 1.09 (95% CI 0.64 to 1.62).
Conclusion: Cardiac risk factor burden has limited clinical value in diagnosing acute coronary syndromes in the ED setting, especially in patients older than 40 years.