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By Ken Grauer, MD
Clinical Scenario: The electrocardiogram (ECG) in the Figure shows normal sinus rhythm at a rate of 80 beats/minute. The PR, QRS, and QT intervals are normal. There is an rSR’ pattern in lead III. The axis is +40°. There is no sign of chamber enlargement. The most remarkable finding on this tracing is the presence of subtle but real ST segment elevation in multiple leads including I, II, aVF, and V2 through V6. The differential diagnosis includes acute infarction, a normal variant (i.e., early repolarization), and acute pericarditis.
Interpretation: The age of the patient in this case makes acute infarction much less likely, especially if there is no history of cocaine ingestion. Also, against a diagnosis of acute infarction is the surprisingly diffuse nature of ST segment elevation in the absence of Q waves, T-wave inversion, and reciprocal ST depression.
The normal variant pattern of early repolarization certainly could be the cause of ST elevation in this case. Not known from the history is whether this ST segment elevation is a new or an old finding. In view of the patient’s age, the chances are good that no prior ECG had been recorded in the past. The J point ST segment elevation with an upward concavity is most likely to represent early repolarization when this ECG pattern is long standing and occurs in an asymptomatic individual in the absence of other signs of acute infarction. However, the characteristic J point "notching" that usually is seen clearly in one or more leads with early repolarization is not present in this tracing, and the history suggests that the patient has symptoms (i.e., chest pain). As a result, rather than the normal variant pattern of early repolarization, the ECG in the Figure well may represent the ECG pattern of acute pericarditis.
The initial stage of acute pericarditis (Stage I) manifests diffuse ST segment elevation, which typically may be seen in many (if not all) leads except III, aVR, and V1. Electrocardiographic pearls that support an ECG diagnosis of acute pericarditis are the fact that leads I and II tend to look similar (as they do here), as compared with the case of acute myocardial infarction in which lead III (rather than lead I) looks similar to lead II. PR segment depression (not seen here) is sometimes another subtle clue to acute pericarditis. Further support usually is forthcoming from the history (most typically revealing a preceding upper respiratory infection in an otherwise healthy young adult leading to development of pleuritic chest pain) and physical exam (the finding of a pericardial friction rub is diagnostic). ST segment elevation seen in the Figure here was new, and the patient in this case did turn out to have acute pericarditis.
Dr. Grauer, Professor and Associate Director, Family Practice Residency Program, Department of Community Health and Family Medicine, College of Medicine, University of Florida, Gainesville, is on the editorial board of Emergency Medicine Alert.