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Make the Diagnosis: Acute Coronary Syndrome

Prior Probability of Acute Coronary Syndrome

About 13% of patients presenting to the emergency department (ED) with acute chest pain will prove to have acute coronary syndrome (ACS).

Population in Whom Acute Coronary Syndrome Should Be Considered

The use of cardiac biomarkers for ED patients with acute chest pain is now ubiquitous. This is done because the biomarkers have high sensitivity and ED physicians do not want to miss ACS. Using biomarkers, history, and electrocardiogram (ECG), ED physicians seek to categorize patients presenting to the ED with chest pain into 1 of 3 groups: ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation ACS (which includes non-STEMI and unstable angina), and noncardiac chest pain. The ECG alone is usually sufficient for diagnosing STEMI. Identifying patients with non-ST-segment elevation ACS requires the combination of clinical information and biomarkers. Biomarkers alone are not sufficient, since some patients with elevated biomarkers do not have ACS, and some patients with ACS do not have elevated biomarkers.

Assessing the Likelihood of Acute Coronary Syndrome

Individual risk factors and chest pain features do have some utility in assessing the likelihood of ACS; a prior abnormal stress test (specificity, 96%; likelihood ratio [LR], 3.1; 95% CI, 2.0-4.7), peripheral arterial disease (specificity, 97%; LR, 2.7; 95% CI, 1.5-4.8), and pain radiation to both arms (specificity, 96%; LR, 2.6; 95% CI, 1.8-3.7) were the clinical findings most suggestive of ACS, and ST-segment depression (specificity, 95%; LR, 5.3; 95% CI, 2.1-8.6) and any ischemia on ECG (specificity, 91%; LR, 3.6; 95% CI, 1.6-5.7) were the most useful ECG findings (see Table 99-1). However, no individual finding is, by itself, sufficient for diagnosing or ruling out ACS. Furthermore, several studies have demonstrated that clinician gestalt alone is not sufficiently sensitive to exclude ACS or significant coronary artery disease at a clinically relevant threshold.1,2

Table 99-1.Useful Findings for Assessing the Likelihood of Acute Coronary Syndrome

Because individual historical and ECG findings are not adequate for ruling out or diagnosing ACS, risk scores have been developed (Table 99-2). Some of the features in risk scores require the clinician to interpret the meaning of patient symptoms, and those features must be ...

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