What are the characteristic EKG (electrocardiogram) changes in pericarditis, including ST elevation and PR depression?

Characteristic EKG Changes in Pericarditis

The characteristic EKG changes in acute pericarditis are widespread ST-segment elevation with upward concavity and PR-segment depression, though these classic findings appear in less than 60% of cases. 1

Diagnostic EKG Criteria

PR-segment depression and widespread ST-segment elevation are the two primary EKG changes used to diagnose acute pericarditis. 1 These changes must be "new" and "widespread" to meet diagnostic criteria, and the presence of either finding (along with one other criterion such as chest pain, pericardial rub, or effusion) is sufficient for diagnosis. 1, 2

Specific EKG Features

The classic EKG pattern includes: 3, 4

• Diffuse, concave upward ST-segment elevations without reciprocal changes (distinguishing it from myocardial infarction)
• PR-segment depressions across multiple leads
• T-wave inversions that develop later in the disease course

The ST elevations typically affect multiple leads simultaneously, reflecting the diffuse nature of pericardial inflammation. 3

Important Clinical Caveats

Frequency and Timing Issues

These classic EKG changes occur in only 25-60% of patients with acute pericarditis, making their absence insufficient to rule out the diagnosis. 5, 6 The EKG may be completely normal at initial presentation or for days after symptom onset. 5

EKG changes are temporally dynamic and evolve rapidly during the disease course, influenced by disease severity, timing of presentation, degree of myocardial involvement, and treatment initiation. 5 Serial EKGs may be necessary to capture these changes, particularly during new episodes of chest pain. 5

Critical Differential Diagnosis

The most dangerous pitfall is misdiagnosing acute myocardial infarction (particularly left circumflex artery occlusion) as pericarditis. 7 Left circumflex occlusion can produce PR depression with multilead ST elevation and ST depression in aVR—mimicking pericarditis exactly. 7

To differentiate acute MI from pericarditis, look for: 7

• QRS widening in leads with ST elevation (suggests MI)
• QT interval shortening in leads with ST elevation (suggests MI)
• Reciprocal ST depression in other leads (suggests MI, not pericarditis)
• Localized rather than diffuse ST changes (suggests MI)

The ST elevation in pericarditis characteristically has upward concavity, while MI typically shows convex or horizontal ST segments. 3, 4

Special Population Considerations

In uremic pericarditis, traditional EKG findings are less reliable, and the EKG should be obtained primarily to exclude acute coronary syndrome rather than to confirm pericarditis. 8 In this population, echocardiography becomes the primary diagnostic tool. 8

Diagnostic Algorithm

When evaluating suspected pericarditis: 1, 2

1. Obtain an EKG in all patients (Class I recommendation)
2. Look for widespread ST elevation with upward concavity and/or PR depression
3. If present, confirm at least one additional criterion: characteristic pleuritic chest pain, pericardial friction rub, or new/worsening pericardial effusion
4. If EKG changes are localized or show reciprocal changes, strongly consider acute MI and proceed with urgent coronary evaluation 7
5. If initial EKG is normal but clinical suspicion remains high, obtain serial EKGs 5
6. Perform echocardiography in all cases to assess for effusion and exclude other diagnoses 1, 3