What are the typical ECG (electrocardiogram) findings in pericarditis?

ECG Findings in Pericarditis

The typical ECG findings in acute pericarditis include widespread ST-segment elevation and PR-segment depression, which are present in up to 60% of cases and reflect inflammation of the epicardium rather than the pericardium itself. 1

Classic ECG Stages of Acute Pericarditis

The ECG changes in acute pericarditis typically evolve through four sequential stages:

Stage I (Early Acute Phase)

• Diffuse, concave upward ST-segment elevation in multiple leads (typically I, II, aVL, aVF, and V3-V6)
• PR-segment depression (opposite to P wave polarity)
• ST-segment depression in lead aVR (almost always)
• Frequent ST depression in V1 (and occasionally in V2)

Stage II (Days Later)

• Early: ST segments return to baseline
• PR segments remain deviated
• Late: Progressive flattening and inversion of T waves

Stage III

• Generalized T wave inversions

Stage IV

• ECG normalizes and returns to pre-pericarditis state

Important Diagnostic Considerations

Distribution and Characteristics

• The ST elevation in pericarditis is widespread and concave upward
• Involves multiple leads without reciprocal changes
• PR depression is a particularly valuable finding that helps differentiate from other causes of ST elevation 1

Temporal Evolution

• ECG changes are highly variable from patient to patient
• Changes evolve rapidly during the course of disease
• May be influenced by disease severity, timing of presentation, degree of myocardial involvement, and treatment 2
• Serial ECGs during episodes of chest pain can be valuable, as ECG may be normal at presentation 2

Diagnostic Challenges

• Classic ECG changes are present in less than 60% of cases 1, 2
• ECG changes reflect epicardial inflammation, as the parietal pericardium itself is electrically inert 1
• Some patients may present with all clinical symptoms of pericarditis but show atypical ECG patterns 3

Differential Diagnosis

Key ECG Differentials

1. Acute coronary syndrome with ST elevation

   • Typically convex (not concave) ST elevation
   • Usually has reciprocal ST depression
   • Localized to anatomic coronary distribution

2. Early repolarization

   • Can mimic pericarditis with ST elevation in leads I and II
   • May show ST depression in aVR and even PR depression
   • Lacks clinical symptoms of pericarditis 4

3. Left circumflex artery occlusion

   • Can present with PR depression, multilead ST elevation, and ST depression in aVR
   • QRS widening and QT interval shortening in leads with ST elevation may help differentiate from pericarditis 5

Clinical Correlation

For accurate diagnosis, ECG findings should be correlated with:

• Characteristic pleuritic chest pain (varies with position and respiration)
• Pericardial friction rub (highly specific but transient, present in 18-84% of cases) 6
• Elevated inflammatory markers (CRP, ESR, WBC)
• Echocardiographic findings (pericardial effusion if present)

Recommendations for ECG Assessment

• ECG is recommended in all patients with suspected acute pericarditis (Class I recommendation) 1
• Serial ECGs may be necessary to capture the evolving pattern
• When ECG findings are atypical, additional imaging (especially echocardiography) is essential 3
• Remember that a normal ECG does not exclude the diagnosis of pericarditis

In summary, while ECG changes are a key diagnostic criterion for pericarditis, clinicians should be aware that these findings may be absent in up to 40% of cases and must be interpreted in the context of the overall clinical presentation.