The ECG changes of acute pericarditis, like those of AMI, go through an evolutionary process over a period of weeks. But, as you will recall from the discussion of the differential diagnoses of ST elevation in Chapter 9, there are significant differences that usually permit us to distinguish between the two.
ST elevation is the usual initial hallmark of both pericarditis and AMI. The ST elevation of pericarditis, however, is usually upwardly concave, widespread throughout all leads, and without reciprocal ST depression.
T wave inversion follows ST elevation as the ST segments return to baseline, but the Q waves seen with AMI never develop.
Another interesting and unique finding with pericarditis is depression of the PR segment. Figure 13.7 is the ECG of a 37-year-old white male with acute viral pericarditis. Note that the PR segments are depressed below the baseline and that there is widespread, upwardly concave ST elevation, without reciprocal depression and without Q wave formation.
Acute pericarditis often undergoes ECG evolution, much as does AMI, except for Q wave formation, which does not occur with pericarditis. ST-segment elevation will show resolution, however, and, as with AMI, T waves may invert.
IIIIII aVR aVL aVF V1 V2 V3 V4V5V6
Figure 13.7. Acute viral pericarditis in a 37-year-old white male. Note the widespread, upwardly concave ST elevation, depressed PR segment, and absence of Q waves or reciprocal depression.
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