A Dangerous Wave: Recognizing the Shark-Fin ECG Sign in STEMI
Avinash Radhakrishna1, Ailis Pollock1, John Cosgrave1
1Department of Cardiology, Saint James's Hospital, Dublin, Ireland.
JACC. Case Reports
|July 30, 2026
Summary
The rare shark-fin morphology on electrocardiogram (ECG) indicates a dangerous ST-elevation myocardial infarction. Prompt recognition of this pattern is crucial for immediate treatment and preventing severe complications.
Area of Science:
- Cardiology
- Medical Diagnostics
Background:
- The shark-fin morphology on an electrocardiogram (ECG) is a rare but critical indicator of ST-segment elevation myocardial infarction (STEMI).
- This pattern signifies profound transmural ischemia, a severe form of heart muscle damage.
Purpose of the Study:
- To highlight the diagnostic significance of the shark-fin morphology in ECGs.
- To emphasize the urgent management required upon identifying this malignant pattern.
Main Methods:
- Case presentation of a 49-year-old man with recurrent chest pain.
- Initial and repeat ECG analysis revealing characteristic shark-fin waveform and ventricular bigeminy.
- Coronary angiography to identify the underlying coronary artery occlusion.
Main Results:
- The patient presented with symptoms suggestive of myocardial infarction.
- Repeat ECG demonstrated a giant triangular QRS-ST-T waveform, indicative of the shark-fin pattern.
- Angiography confirmed subtotal occlusion of the proximal left anterior descending artery.
Conclusions:
- The shark-fin morphology is a rare, malignant STEMI pattern that can be mistaken for other wide-complex ECG abnormalities.
- Immediate recognition necessitates urgent reperfusion therapy.
- Vigilance for potential complications such as cardiogenic shock and ventricular fibrillation is essential.
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