Cardiac Risk Factor Burden in Diagnosing ACS in the ED Setting

Abstract & Commentary

By John Shufeldt, MD, JD, MBA, FACEP, Chief Executive Officer, NextCare, Inc.; Attending Physician/Vice Chair, Department of Emergency Medicine, St. Joseph's Hospital and Medical Center, Mesa, AZ, is Editor for Urgent Care Alert.

Dr. Shufeldt reports no financial relationship to this field of study.

Synopsis: Cardiac risk factor burden has limited clinical value in diagnosing acute coronary syndromes in the ED setting, especially in patients older than 40 years.

Source: Jan JH, et al. The role of cardiac risk factor burden in diagnosing acute coronary syndromes in the emergency department setting. Ann Emerg Med. 2007;49:145-152.

The object of this original study was to determine if the burden of cardiac risk factors, defined as the number of conventional cardiac risk factors present, is useful in the diagnosis of acute coronary syndromes (ACS).

The study was a post hoc analysis of acute coronary syndrome patients who were registered on the Internet Tracking Registry of Acute Coronary Syndromes. This was a multi-center, multi-site study of 17,713 patients in the United States and Singapore. (Patients from Singapore were ultimately excluded secondary to a different set of risk factors associated with ACS.) Patients were entered in the study if they were older than 18 years of age, if the physician suspected they had acute coronary syndrome, provided, however, that they were not on cocaine or methamphetamine and they did not leave against medical advice, provided the researchers had complete ECG and demographic data.

Acute coronary syndrome was defined by revascularization within 30 days, diagnostic-related group codes, or death within 30 days, with positive cardiac bio markers at hospitalization. Cardiac risk burden was defined as the number of the following factors present at hospitalization: diabetes, hypertension, smoking, hypercholesterolemia, and family history of coronary artery disease. The patient population was broken down into 3 subgroups: < 40-years-old, 40 to 65-years-old, and > 65-years-old.

Ultimately, 10,806 patients were included in the study; 871 had acute coronary syndrome defined by the aforementioned inclusion criteria. In the group of patients younger than 40, having no risk factors had a negative likelihood ratio of 0.17 (95%; CI, 0.04 to 0.06), and having 4 or more risk factors had a positive likelihood ratio of 7.39 (95%; CI, 3.09 to 17.67). In the 40 to 60 age group, 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 the patient group over 65, 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).

Other studies support the fact that as the number of cardiac risk factors increased, the odds of ACS increased incrementally.1-3 In the population-based Framingham Heart Study, researchers found that individuals with 2 or more cardiac risk factors had a much higher risk of death as compared to patients with one or no risk factors.4

Jan and colleagues also found that the risk of ACS was significantly modified by age. For example, in the patients over 65, cardiac risk factor burden was less useful for predicting ACS, reflecting that age itself is a powerful risk factor for the development of acute coronary syndrome.

Commentary

This study is useful to those of us in urgent care centers who are using point-of-care cardiac enzymes. The data suggest that in patients under 40 years old, providers should use cardiac risk factor burden to augment their clinical decision making. In those patients who are over 40, clinicians should not rely on the absence of cardiac risk factors to predict whether or not a patient is having a cardiac-related condition.

Patients often present to the urgent care center with a chief complaint of chest pain, or other potential anginal equivalents. Oftentimes, one of the major factors used to decide whether or not a transfer to the hospital is necessary is the presence or absence of additional cardiac risk factors.

This study suggests that the presence or absence of those risk factors in patients over 40 should not tip the balance either way. Moreover, the absence of risk factors has limited clinical value in diagnosing acute coronary syndrome, particularly in patients who are older than 40 years of age. For those patients with a normal EKG and a negative troponin, the story still buys the admission.

References

  1. Braunwald E, et al. Heart disease: A textbook of cardiovascular medicine. 7th ed. Philadelphia, PA Elsevier Saunders; 2005
  2. Snowden CB, et al. Predicting coronary heart disease in siblings — A multivariate assessment: The Framingham Heart Study. Am J Epidemiol. 1982;115:217-222.
  3. Rosenmen RH, et al. Coronary heart disease in Western Collaborative Group Study. Final follow-up experience of 8 ½ years. JAMA. 1975;233:872-877.
  4. Lloyd-Jones DM, et al. Prediction of lifetime risk for cardiovascular disease by risk factor burden at 50 years of age. Circulation. 2006;113:791-798.