Myth: identifying classic coronary risk factors helps to predict the likelihood of acute ischemia.

Abstract

Since the initial findings of the Framingham and other longitudinal studies, clinicians are well aware of the risk factors for the development of coronary artery disease: age, male gender, hypercholesterolemia, diabetes, smoking, hypertension, and family history of myocardial infarction.1 It has become routine for physicians to identify these risk factors in patients presenting to the emergency department with signs and symptoms of acute cardiac ischemia. Moreover, emergency department clinicians are using the presence or absence of these “classic” risk factors in addition to clinical presentation and electrocardiographic (ECG) findings to make decisions regarding the ultimate disposition of these patients. In this manner, many clinicians routinely consider patients without coronary risk factors at low risk for acute coronary syndromes even when they present with chest pain. But Selker et al have shown that using a patient's coronary risk factors in the emergency department setting does not improve a physician's ability to diagnose acute ischemia.2 The confusion about the use of risk factors stems from a misinterpretation of their predictive value. The classical coronary risk factors have been repeatedly shown to increase the risk of ischemic heart disease in patients followed over many years. But in the acute setting, physicians need to obtain patient data that will predict the risk of acute cardiac ischemia and—even more importantly—the risk of adverse events during that particular encounter. Factors that predict the development of ischemic heart disease over years, rather than acute events, are not helpful in the emergency department or acute care setting, and they may be seriously misleading. By obtaining clinical data and reports of classical coronary risk factors, Selker et al performed a prospective study to determine whether the presence of the classical coronary risk factors increases the likelihood of acute cardiac ischemia beyond that expected from clinical presentation and ECG findings. Over 5,000 patients were enrolled, and logistic regression was used to calculate the relative risk of each coronary risk factor in predicting acute ischemia. They found that in men presenting to the emergency department with signs and symptoms of acute ischemia, the relative risk of cardiac ischemia for each classic risk factor was as follows: hypertension 1.0 (95% confidence interval [CI], 0.7-1.0), diabetes 2.4 (95% CI, 1.2-4.8), cigarette smoking 1.5 (95% CI, 1.0-2.4), and family history of myocardial infarction at younger than 50 years 1.5 (95% CI, 0.7-2.8). In contrast, the relative risk of acute ischemia in patients complaining of chest pain was 12.1 (95% CI, 5.3-27.6), and in those with ischemic ECG changes it was 8.7 (95% CI, 5.0-14.8). The 1.5- to 2-fold relative risk of acute ischemia found in patients with diabetes and family history is extremely small in comparison. The study also found that in women, none of the classic risk factors increased the relative risk of acute ischemia beyond that of the history and ECG findings. Goldman et al studied 10,000 patients with acute chest pain to identify possible clinical predictors of the development of major complications.3 These factors included older age, male gender, pain similar to prior myocardial infarction, systolic blood pressure less than 110 mm Hg, and initial ECG changes.