What are the characteristic EKG (electrocardiogram) changes in pericarditis?

Characteristic ECG Changes in Pericarditis

The classic ECG changes in pericarditis include widespread ST-segment elevation and PR-segment depression, occurring in approximately 60% of cases. 1

Stages of ECG Changes in Pericarditis

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

Stage I (Early Acute Phase)

• Widespread concave ST-segment elevation in anterior and inferior leads (I, II, aVL, aVF, V3-V6)
• PR-segment depression (opposite to P wave polarity)
• ST-segment depression in aVR (always), frequently in V1, and occasionally in V2 1

Stage II

• Early Stage II: ST junctions return to baseline, PR-segment remains deviated
• Late Stage II: T waves progressively flatten and invert 1

Stage III

• Generalized T wave inversions 1

Stage IV

• ECG returns to pre-pericarditis state 1

Key Diagnostic ECG Features

1. Lead Distribution: Typical involvement in leads I, II, aVL, aVF, and V3-V6 1
2. ST Morphology: Concave upward ("saddle-shaped") ST elevation
3. PR Depression: Characteristic finding that helps differentiate from other causes of ST elevation
4. Absence of Reciprocal Changes: Unlike in STEMI, reciprocal ST depression in other territories is typically absent
5. Ratio Assessment: In lead V6, pericarditis is likely if the J point is >25% of the height of the T wave apex (using PR segment as baseline) 1

Differentiating from Mimics

Acute Coronary Syndrome

• Pericarditis: Diffuse ST elevation, concave upward, PR depression
• STEMI: Localized ST elevation, often convex upward, with reciprocal ST depression

Early Repolarization Pattern

• Both can show ST elevation, but early repolarization typically has:
• J-point elevations with slurring or notching at the end of the QRS complex
• No acute evolution of ECG changes (unlike pericarditis)
• No PR depression 1, 2

Perimyocarditis

• May show additional signs of myocardial involvement:
• Regional wall motion abnormalities
• Elevated cardiac biomarkers (troponin I, CK-MB) 1, 3

Pitfalls and Caveats

1. Normal ECG Possible: Up to 40% of pericarditis cases may not show classic ECG changes 4
2. Temporal Variability: ECG changes evolve rapidly and may be influenced by disease severity, timing of presentation, and treatment 4
3. Missed Diagnosis: Serial ECGs may be necessary, as changes can develop days after initial presentation 4
4. Misdiagnosis Risk: Left circumflex artery occlusion can occasionally mimic pericarditis ECG patterns with PR depression, multilead ST elevation, and ST depression in aVR 5
5. QRS and QT Assessment: QRS widening and QT interval shortening in leads with ST elevation may suggest STEMI rather than pericarditis 5

Clinical Correlation

For accurate diagnosis of pericarditis, ECG findings should be correlated with:

• Characteristic chest pain (typically pleuritic, positional)
• Pericardial friction rub on auscultation
• Presence of pericardial effusion on imaging
• Elevated inflammatory markers (CRP, ESR, WBC) 1, 6

When ECG findings are ambiguous, cardiac MRI can provide definitive assessment of pericardial inflammation and myocardial involvement 6.