Osborn Wave on ECG
The Osborn wave is a distinctive positive deflection (notch) occurring at the junction between the QRS complex and ST segment, classically associated with hypothermia but also seen in other conditions, and it carries important arrhythmogenic implications requiring prompt recognition and treatment of the underlying cause. 1
Definition and ECG Characteristics
The Osborn wave appears as a low-frequency deflection at the end of the QRS complex, creating a dome-shaped or "camel's hump" configuration at the R-ST junction. 1, 2 The American Heart Association defines this as a terminal QRS notch that was initially described by Osborn as "J waves" referring to injury during experimental hypothermia. 1
Key morphologic features include:
- Positive deflection immediately following the QRS complex 3, 4
- Elevation of the J point at the QRS-ST junction 4
- Amplitude and duration inversely proportional to core body temperature in hypothermic patients 2
- The J point should be measured at the peak of the notch when present 1, 5
Clinical Causes and Associations
Primary Association: Hypothermia
Osborn waves appear in approximately 80% of hypothermic patients with core body temperature ≤32-35°C (≤95°F). 2, 4 The waves typically:
- Become more prominent as temperature decreases 2, 6
- Resolve with rewarming, as demonstrated by repeat ECGs showing disappearance after appropriate warming 4
- May manifest as prominent J point elevation mimicking ST-segment elevation MI (STEMI) 1
Non-Hypothermic Conditions
Osborn waves are not pathognomonic of hypothermia and can occur in normothermic patients. 2, 6 Other causes include:
- Myocardial ischemia (where they carry particularly high arrhythmogenic risk) 6
- Hypercalcemia 6
- Brain injury 6
- Sepsis 6
Clinical Significance and Arrhythmogenic Risk
The most critical implication of Osborn waves is their arrhythmogenic potential, particularly as precursors to malignant ventricular arrhythmias including ventricular fibrillation. 6, 7
Risk Stratification
- In hypothermic patients, Osborn waves are associated with atrial fibrillation (up to 50% of cases), ST segment changes, Brugada syndrome morphology, and QT prolongation 1, 3
- When observed with myocardial ischemia, they significantly increase risk of ventricular fibrillation and sudden cardiac death 6
- The presence of Osborn waves warrants continuous cardiac monitoring to detect progression to ventricular arrhythmias 4, 7
Critical Diagnostic Pitfall: Distinguishing from STEMI
A major clinical pitfall is misinterpreting Osborn waves as ST-segment elevation from acute myocardial infarction. 1, 4
Key differentiating features:
- Osborn waves create a distinct notch or dome at the QRS-ST junction, not smooth ST elevation 1, 3
- In hypothermia or targeted temperature management, the "ST elevation" resolves with rewarming, representing normal physiological response rather than ischemia 1
- Clinical context is essential: check core body temperature in all patients with suspected Osborn waves 4
- After defibrillation, up to 25% of patients exhibit ST elevation that decreases within 5 minutes, which differs from persistent Osborn waves 1
Relationship to J-Wave Syndromes
Osborn waves represent part of a spectrum of J-wave abnormalities that includes early repolarization syndrome and Brugada syndrome. 1, 5 Important distinctions:
- Terminal QRS notches (Osborn waves) differ from terminal QRS slurs, which show abrupt slope changes rather than distinct deflections 1, 5
- Brugada pattern shows downward coved or saddleback ST-segment elevations in V1-V3, distinct from the dome-shaped Osborn wave 1, 5
- Epsilon waves in arrhythmogenic right ventricular cardiomyopathy are low-amplitude terminal QRS deflections in anteroseptal leads, morphologically different from Osborn waves 1, 5
Management Implications
For Hypothermic Patients
- Initiate aggressive rewarming measures immediately 4
- Provide supportive care including IV crystalloid resuscitation 4
- Continuous cardiac monitoring is mandatory to detect arrhythmias 1, 4
- Adjust ST-segment monitoring alarm settings during rewarming to avoid false alarms as Osborn waves resolve 1
For Targeted Temperature Management
- In post-cardiac arrest patients undergoing therapeutic hypothermia, expect Osborn waves with height proportional to degree of hypothermia 1
- Carefully differentiate new ischemic patterns from hypothermia effects to avoid unnecessary interventions 1
- Arrhythmia monitoring including QTc monitoring is indicated (Class I recommendation) 1
General Approach
- Perform 12-lead ECG in all patients with hypothermia 4
- Treat the underlying cause (hypothermia, ischemia, electrolyte abnormalities) 4, 6
- Recognition of Osborn waves, while not specific or predictive of outcome, serves a pivotal role in preventing progression to ventricular arrhythmia through prompt intervention 4