Acute cardiac ischemia in patients with syncope: importance of the initial electrocardiogram

To determine the prevalence of acute cardiac ischemia in emergency department (ED) syncope patients without chest pain and to determine which of these patients are at high risk for acute cardiac ischemia.

Data were collected prospectively during a study of ED triage of patients who had had possible acute cardiac ischemia. Supplemental retrospective review of records was performed to differentiate syncope from dizziness.

Six hospital EDs in New England (two primary teaching hospitals in urban locations, two medical-school-affiliated teaching hospitals, and two nonteaching hospitals in rural settings).

5,762 patients had presented to the ED with chief complaints consistent with acute cardiac ischemia, including chest pain, shortness of breath, dizziness, and syncope. The study sample consisted of 251 patients who had had syncope and no chest pain.

The prevalence of acute cardiac ischemia among the syncope patients was 7% (18 of the 251 patients). Univariate analysis revealed the following to have significant association with acute cardiac ischemia: ischemic abnormalities on the electrocardiogram (ECG) obtained in the ED (p less than 0.001), arm or shoulder pain on presentation (p less than 0.05), rales (p less than 0.1), and prior history of exercise-induced angina (p less than 0.05) or myocardial infarction (p less than 0.1). All 18 patients with acute cardiac ischemia had ischemic abnormalities (pathologic Q waves, ST-segment elevation or depression, or T-wave abnormalities) on their presenting ECGs.

For syncope patients who have no chest pain or ischemic abnormality on the presenting ECG in the ED, acute ischemia appears to be unlikely. Admission to the cardiac care unit for these patients for possible myocardial ischemia is probably unnecessary. However, patients who have syncope and ischemic abnormalities on the ECG are at risk for acute cardiac ischemia, even in the absence of chest pain. Hospital admission to rule out myocardial infarction for these patients is prudent.