Last updated 2/7/26
QRS Notching
What Is QRS Notching?
QRS notching refers to a small, discrete deflection at the terminal portion of the QRS complex, most often just before the ST segment begins. It appears as a subtle “bump” rather than a separate wave.
This finding is most commonly associated with early repolarization and pericarditis. Notching is most frequently seen in the precordial leads, particularly lateral leads (V4–V6), but it can appear in any lead.
ECG - Early Repolarization
ECG - Acute Pericarditis
From LITFL
Common Pitfall
Many authors have described this finding as almost always benign. In real-world emergency medicine, “always” is dangerous language. Rare exceptions exist. A patient with baseline early repolarization and QRS notching may still develop acute coronary occlusion, with new ischemic ST changes superimposed on a prior benign pattern.
ECG - Anterior MI + QRS notching
From Emergency Medicine Cases
QRS notching is often reassuring, but can be present with other dangerous pathologies.
Osborn Waves
What Is an Osborn Wave?
An Osborn wave, also called a J wave, is a large, prominent deflection at the end of the QRS complex seen in patients with hypothermia.
Unlike QRS notching, Osborn waves are:
- Taller
- Wider
- Often appear as an extra wave following the QRS
- Can mimic an RSR′ pattern if misread
Do not confuse QRS notching with an Osborn (J) wave. They are not variations of the same finding.
ECG Osborn Waves (91F)
ECG Massive Osborn Waves
Key Features of Osborn Waves
- Amplitude increases as core temperature decreases
- Often accompanied by:
- Bradycardia
- Atrial fibrillation
- QT prolongation
- ST depression and T-wave inversion (when large)
- Artifact is frequent due to loss of thermoregulation
The exact electrophysiologic mechanism remains unclear, but the association with hypothermia is consistent and reproducible.
ECG - Bradycardia + impressive Osborn waves
ECG - Shivering artifact (82F) + Osborn wave in V4
Osborn waves occur in any cause of hypothermia, including:
- Environmental exposure
- Sepsis
- Severe hypothyroidism
- Addison’s disease
- Intoxication
ECG - Non-evironmental hypothermia from myxedema and sepsis (89F)
Hypothermia is associated with marked cardiac irritability.
- Core temperatures <32°C significantly increase the risk of:
- Ventricular dysrhythmias
- Ventricular fibrillation triggered by movement
When you see Osborn waves, handle the patient gently. Even routine movement can precipitate lethal arrhythmias.
ECG Pattern Recognition: QRS Notching vs Osborn
Feature | QRS Notching | Osborn (J) Wave |
Size | Small, subtle | Large, prominent |
Width | Narrow | Broad |
Significance | Benign variant | Pathologic |
Associated condition | Early repolarization, pericarditis | Hypothermia |
ST elevation | Usually benign | May coexist with other abnormalities |
Clinical risk | Low | High (arrhythmogenic) |
Take-Home Summary
- Terminal QRS notching + ST elevation → often benign but can still be present with other abnormalities
- Osborn waves = hypothermia until proven otherwise
- Size, width, and clinical context separate the two
- ECG findings should guide urgency, not replace bedside judgment
Sources
- Emergency Medicine Cases. Early repolarization vs anterior STEMI and ECG mimics. Emergency Medicine Cases website. https://emergencymedicinecases.com. Accessed February 7, 2026.
- Garcia TB. 12-Lead ECG: The Art of Interpretation. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2015.
- Life in the Fast Lane (LITFL). ECG library: Pericarditis; Osborn (J) waves; Early Repolarisation LITFL website. https://litfl.com. Accessed February 7, 2026.
- Mattu A, Brady WJ. ECGs for the Emergency Physician. Vols 1–2. Philadelphia, PA: Elsevier; 2003–2008.
- Surawicz B, Knilans TK. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric. 6th ed. Philadelphia, PA: Elsevier Saunders; 2008.
This post is for education and not medical advice.