The shark fin sign is indicative of severe myocardial injury and is associated with a large burden of myocardial ischemia, its recognition is crucial for timely diagnosis and management of STEMI.
The shark fin sign is also known as ‘lambda waves', 'giant R waves', or 'triangular waves’.
The ECG pattern consists of complexes formed by the blurring together of QRS and T-wave due to extreme ST-deviation.
The shark fin sign is associated with STEMI of the left main coronary artery or proximal left anterior descending artery.
The shark fin sign can also be found in takotsubo cardiomyopathy, which is associated with hemodynamic instability and shock.
Figure 1 is an ECG from Doctor Smith’s ECG Blog, showing shark fin sign of massive infero-posterior STEMI in a 75-year-old man who collapses to the ground in cardiac arrest while shopping.
Figure 2 is another ECG from Doctor Smith’s ECG Blog, showing shark fin sign of STEMI due to occlusion of the left main coronary artery in a 55-year-old lady who presents with severe chest pain.
Figure 3 is an ECG originally published in Dr. Wang's Atlas of Electrocardiography, showing shark fin sign of STEMI. Note that, the shark fin ST-elevation in leads V4 and V5 could easily be mistaken for a wide-complex tachycardia on ECG rhythm strips.
This is an ECG published in ”Circulation“, showing shark fin sign in a 54-year-old female with septic shock, who was finally proved to be due to takotsubo cardiomyopathy. In a critically ill patient with shark fin sign on ECG and septic shock, takotsubo cardiomyopathy needs to be considered, and takotsubo cardiomyopathy should be included in the differential diagnosis for patients with sepsis and ST elevation that mimics STEMI.
Take Home Message
In conclusion, the shark fin sign is an uncommon ECG pattern and is associated with high-risk conditions such as sub-occlusion of the left main coronary artery or proximal left anterior descending artery.
It can also be found in takotsubo cardiomyopathy, which is associated with hemodynamic instability and shock.