Introduction:
We sought to (1) classify patients who underwent stress echocardiography in an emergency department observation unit based on their pretest probabilities of obstructive CAD using the Diamond-Forrester criterion, (2) to compare observed versus expected frequencies of obstructive CAD based on the Diamond-Forrester risk categories of low (<25%), intermediate (25-75%), and high (>75%) pretest probability of disease, and (3) to test the association of traditional cardiovascular risk factors (age, gender, hypertension, diabetes, high cholesterol, and smoking) with obstructive CAD.
METHODS:
Retrospective review of the electronic medical record for patients who presented to the emergency department with chest pain and underwent observation followed by stress echocardiography between the period January 1, 2012 to December 31, 2012. Patients were classified as low, intermediate, or high risk for obstructive CAD using the Diamond-Forrester criterion. Main outcome measures were stress echocardiography results as well as receipt of cardiac catheterization and results.
RESULTS:
A total of 504 patients were included in the final analysis. Overall, 4.8% had a positive stress test and only 1.2% had angiographic evidence of obstructive CAD. In each category of risk, the observed frequency of obstructive CAD was significantly lower than expected. Having a high pretest probability as defined by the Diamond-Forrester criterion was significantly associated with obstructive CAD. Age, gender, diabetes, hypertension, high cholesterol, and smoking were not independently associated with evidence of obstructive CAD; nor were any composites of these risk factors.
CONCLUSIONS:
The traditional Diamond-Forrester criterion significantly overestimates the probability of obstructive CAD in ED observation unit patients. Reliance on the Diamond-Forrester criterion and other traditional risk factors associated with obstructive CAD in the outpatient setting could lead to faulty Bayesian reasoning, overuse of non-invasive imaging, and improper interpretation of test results in an ED population of low-risk chest pain patients. Further work is required to determine an optimal risk-assessment strategy for this patient population.
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