Differential Diagnosis of ST Elevation

Acute myocardial infarction is not the only condition that can cause ST-segment elevation. Several other conditions, including pericarditis and benign early repolarization changes (a normal variant of ST elevation commonly seen in healthy young adults), routinely produce ST elevation. It is important, therefore, to distinguish STEMI from other causes of ST elevation.

Several distinguishing criteria can be helpful. First, as described earlier in this chapter, the ST elevation of AMI is often accompanied by reciprocal depression in the wall opposite the infarction. Pericarditis and benign early repolarization changes, however, show no reciprocal depression but, instead, show ST elevation in all walls. In other words, the ST elevation is not localized to one wall, but is widespread and is reflected in more than one ECG region of the heart.

Figure 9.15 shows the tracing of a young adult male with acute pericarditis. Note that the ST elevation is widespread throughout the inferior, anterior, and lateral walls, and that there is no reciprocal depression. Another very helpful clue that this tracing represents pericarditis rather than STEMI is the presence of PR-segment depression. Note that the PR segment shows slightly downsloping depression in all leads. This finding is characteristic of pericarditis.

Figure 9.16 is the tracing of a healthy, asymptomatic 34-year-old male who has no clinical evidence of pericardial or myocardial disease. This tracing is typical of benign early repolarization changes and, like pericarditis, shows widespread ST elevation without reciprocal depression. Unlike pericarditis, however, there is no PR-segment depression.

Differential Diagnosis of ST Elevation 77

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Figure 9.15. Acute pericarditis. Note that there is widespread ST elevation that is upwardly deeply concave in the anterior, inferior, and lateral walls. In addition, there is no reciprocal depression and there are no Q waves,

A second helpful distinguishing criterion between AMI and these other two causes of ST elevation is that the ST-segment elevation of AMI is typically upwardly convex or only very slightly concave. Note in Figures 9.15 and 9.16, however, that the ST elevation of pericarditis and benign early repolarization changes is typically downwardly convex.

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Figure 9.16. Benign early repolarization changes. Note that, as in pericarditis, there is widespread ST elevation that is upwardly concave, although it is usually not as high as in pericarditis. In addition, there is no reciprocal depression, and there are no Q waves or T wave inversions.

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