ECG in Pericarditis

ECG changes are present in 90% of cases and are important for the differential diagnosis. The ECG is most typical in the early phase of the disease. ST segment elevations are often found in many, if not all, ECG leads. In contrast to myocardial infarction the ST segment elevation is oftenupwardly concave. Typical for the early phase of acute pericarditis is the depression of the PQ segment. In the aVR lead, the ST segment and PQ changes are inverted, i. e., in aVR, PQ is elevated and the ST segment is depressed. In the course of pericarditis ST segment elevation abates and the Twave becomes flat or normal. After normalization of the ST segment, diffuse T wave inversions are occasionally recorded. With the development of a pericardial effusion a peripheral low-voltage and electric alternans that is caused by floating of the heart in the large pericardial effusion, may be registered. In the absence of simultaneous myocardial ischemia, changes in the QRS complex, such as broadening of the QRS, or rhythm disturbances, such as AV blockade or extrasystole, suggest a myocarditis.

The differentiation of these changes from an acute myocardial infarction might be difficult. In myocardial infarction ST segment elevations are often monophasic or convex upward, in general, higher and localized over the infarct region. In addition, in pericarditis no pathologic Q waves develop. In “early repolarization” the ST segment elevations resemble that of acute pericarditis.However, there is in general no PQsegment depression and the T waves are tall and pointed.