Acute painful pericarditis occurs in less than 10%of patients with RA during their lifetime. The major clinical manifestations of acute pericarditis are chest pain, pericardial friction rub, and the classic finding of widespread saddle-shaped or concave-up ST-segment elevation on ECG.
While both acute pericarditis and acute MI can present with chest pain and elevations in cardiac biomarkers, the ECG changes in acute pericarditis differ from those in STEMI in several ways, as discussed by reviewing the other choices below.
Choices (A) and (B) : The ST-segment elevation in acute pericarditis begins at the J point, which represents the junction between the end of the QRS complex (termination of depolarization) and the beginning of the ST-segment (onset of ventricular repolarization). The ST-segment elevation rarely exceeds 5 mm and usually retains its normal concavity. On the other hand, the typical finding in a patient with STEMI is convex (dome-shaped) ST-segment elevation (a pattern not characteristic of acute pericarditis) that may be more than 5 mm in height.
In pericarditis, the ST changes are more generalized and typically are present in most leads because the pericardium envelopes the entire heart. Additionally, in pericarditis the ST-segment elevation in the precordial leads is most commonly seen in V5 and V6, and in decreasing frequency from V4 to V1, while in the limb leads it is most evident in leads I and II than in leads III, aVF, and aVL.
Choice (C): Acute STEMI is often associated with reciprocal ST-segment changes, which are not seen with pericarditis except in leads aVR and V1. Concomitant ST-segment elevation and T-wave inversions do not generally occur simultaneously in pericarditis, although they commonly coexist in acute STEMI.
Choice (D): PR-segment elevation in aVR with PR depression in other leads due to a concomitant atrial current of injury is frequently seen in acute pericarditis but rarely in acute STEMI.
Choice (E): Prolongation of the QT interval with regional T-wave inversion (in the absence of certain drugs) favors the diagnosis of myocardial ischemia over pericarditis alone.
Chest radiography is typically normal in patients with acute pericarditis. Acute pericarditis may be associated with increases in serum biomarkers of myocardial injury such as cardiac troponin I or T.
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