ECG Topic - Pericarditis

Last updated September 28, 2025

Introduction

Acute pericarditis is inflammation of the pericardial sac, typically causing sharp, pleuritic, positional chest pain. Its ECG findings can mimic STEMI and Early Repolarization, but no single feature is pathognomonic. The most characteristic patterns are outlined below.

ECG findings

Diffuse Concave ST Elevation with reciprocal STD in aVR (± V1)

• Pericardial/epicardial inflammation produces a global “current of injury,” elevating ST segments diffusely; aVR (±V1) shows reciprocal depression.

Diffuse PR Segment Depression w/ reciprocal PR elevation in aVR

• Atrial inflammation shifts the baseline downward (PR depression), with aVR showing reciprocal PR elevation — a relatively specific marker for pericarditis.

Spodick’s Sign

• Downward slanting of the TP segment, most evident in the inferior (II, III, avF) and lateral leads (e.g., V5–V6), reflecting pericardial irritation; useful but not universally present (29% sensitive) and present in 5% of STEMIs.

Sinus tachycardia, low voltage and electrical alternans.

• Sinus tachycardia may be a nonspecific response to pain/fever or a compensatory response to concomitant myocarditis / heart failure / pericardial effusion. Low voltage and beat-to-beat QRS amplitude variation (electrical alternans) suggest pericardial effusion. Low voltage is defined as either QRS amplitude ≤ 5 mm in all limb leads or ≤ 10 mm in all precordial leads.

A patient diagnosed with myopericarditis and a large pericardial effusion (had negative cath) Note the QRS alternans in the rhythm lead in V1. There is additionally aVL depression which suggests simultaneous myocardial injury and hence cath lab activation.

Pericarditis vs STEMI / OMI

ECG Example - Pericarditis or OMI?

ECG Example - Pericarditis or OMI?

Pericarditis vs Early Repolarization

Examples of J-point notching in Early Repolarization

From LITFL.com

ST/T ≥ 0.25 in V6

This comes from a couple small papers but not validated in large prospective ED cohorts. Studies are small and may overestimate accuracy

• Wang et al., 2003 (Am J Cardiol 92:1290–1293)
• Retrospective analysis of 35 pericarditis vs. 35 BER cases.
• ST/T ratio >0.25 in V6: sensitivity ~82%, specificity ~80% for pericarditis.
• Subsequent validation studies (small case series and ECG reviews; e.g., Brady WJ et al., Am J Emerg Med 1999; Adler et al.)
• Sensitivity ranges 70–90%, specificity 75–85% in small cohorts.

ECG Example - Pericarditis or Early Repolarization?

ECG Example - Pericarditis or Early Repolarization?

Key Points

• Pericarditis often mimics STEMI and early repolarization, but no single ECG finding is diagnostic — interpretation requires pattern recognition and clinical context.
• Diffuse concave ST elevation with reciprocal ST depression in aVR (±V1) is the most classic pattern; PR depression with reciprocal PR elevation in aVR is relatively specific when present.
• Spodick’s sign (downsloping TP segment) supports pericarditis but is low sensitivity (~30%) and not entirely specific (seen in ~5% of STEMIs).
• Sinus tachycardia, low voltage, and electrical alternans point toward large pericardial effusion rather than isolated pericarditis.
• Key STEMI differentiators: regional rather than diffuse ST elevation, convex/tombstone morphology, reciprocal ST depression beyond aVR/V1, and Q-wave or R-wave progression loss.
• Key BER differentiators: stable pattern over time, prominent J-point notching (“fish-hook”) in V4, ST/T ratio in V6 <0.25 (vs >0.25 favoring pericarditis).
• Always integrate clinical features (pleuritic, positional pain, friction rub, recent viral illness) and, if uncertain, use serial ECGs and bedside echo to clarify diagnosis.

References

1. Adler A, Nikus K, Birnbaum Y. Electrocardiographic differential diagnosis of acute pericarditis, benign early repolarization, and ST-elevation myocardial infarction. Ann Noninvasive Electrocardiol. 2012;17(2):141-145. doi:10.1111/j.1542-474X.2012.00489.x
2. Bhardwaj A, Kumar V, Aggarwal S, et al. Utility of ST/T ratio in differentiating acute pericarditis from early repolarization and left ventricular hypertrophy patterns. Am J Med Sci. 2013;346(4):289-294. doi:10.1097/MAJ.0b013e318262c2a8
3. Brady WJ, Mattu A, Tabas JA. Critical Decisions in Emergency and Acute Care Electrocardiography. Wiley-Blackwell; 2009.
4. Brady WJ, Chan TC, Pollack M. Electrocardiographic manifestations: acute pericarditis. Am J Emerg Med. 1999;17(7):768-775. doi:10.1016/S0735-6757(99)90190-0
5. Chou TC, Surawicz B. Chou’s Electrocardiography in Clinical Practice. 6th ed. Saunders/Elsevier; 2008.
6. Davila C. The ECG. Updated ed. Self-published; 2024.
7. ECG Essentials. Pericardial Disease. Published April 29, 2025. Accessed September 27, 2025.
8. Life in the Fast Lane (LITFL) ECG Library. Pericarditis. Published August 1, 2020. Accessed September 27, 2025.
9. Podrid PJ. Podrid’s Real-World ECGs: A Master’s Approach to the Art and Practice of Clinical ECG Interpretation. Vol 6. Cardiotext Publishing; 2016.
10. Sarda AK, Thute P. Importance of ECG in the diagnosis of acute pericarditis and myocardial infarction: a review article. Cureus. 2022;14(10):e30633. doi:10.7759/cureus.30633
11. Wang K, Asinger RW, Marriott HJL. ST-segment elevation in conditions other than acute myocardial infarction. N Engl J Med. 2003;349:2128-2135. doi:10.1056/NEJMra022580
12. Wave Maven. ECG Wave Maven—Pericardial Disease Library. Accessed September 27, 2025. https://ecgwavemaven.com
13. Zhan ZQ, Nikus K, Birnbaum Y. PR depression with multilead ST elevation and ST depression in aVR by left circumflex artery occlusion: how to differentiate from acute pericarditis. Ann Noninvasive Electrocardiol. 2020;25(6):e12752. doi:10.1111/anec.12752

This post is for education and not medical advice.