Introduction: Shark fin sign, also known as triangular QRS-ST-T waveform (TW), is characterized by a giant R wave (amplitude ≥ 1 mV) resulting from the fusion of the QRS complex, the ST-segment and the T wave and showing triangular morphology. TW pattern is quite uncommon and reveals a life-threatening condition that needs aggressive management.
Case presentation: A 45-year-old black man with history of arterial hypertension and without known comorbidities arrived at our emergency department (ED) with out-of-hospital cardiac arrest (OHCA). Return of spontaneous circulation occurred after 11 minutes and 2 direct current shocks. At arrival in the ED, he was hemodynamically stable, electrocardiogram showed atrial fibrillation without repolarization abnormalities, and echocardiogram revealed left ventricular hypertrophy and hypokinesia of the mid-basal inferior wall. Plasma level of electrolytes and high-sensitivity troponin were in range. Sedation in the ED was needed due to psychomotor agitation. He was transferred to the cardiac intensive care unit; no arrhythmias were noted. During the night, electrocardiogram monitoring revealed a progressive ST segment elevation in inferior leads up to a triangular QRS-ST-T giant waveform (“Shark fin sign”), confirmed at 12-lead electrocardiogram. After 3 minutes the electrocardiogram showed a progressive and complete resolution of ST-elevation. Akinesia of the inferior wall was confirmed at echocardiogram. The episode repeated 5 more times in the following 40 minutes, while waiting for the arrival of the Cath lab personnel. Coronary angiography revealed a sub-occlusive mid right coronary artery (RCA) stenosis. Percutaneous coronary intervention with the implantation of one drug eluting stent was performed. After the procedure the patient was hemodynamically stable, and the ECG did not show any other abnormality and no episodes of recurrent ST-elevation occurred.
Conclusion: The shark fin sign refers to the abrupt total deprivation of blood flow in large areas of myocardium that are seen during coronary thrombotic occlusion or vasospasm. In our case we assisted to transient but repetitive inferior triangular ST-elevation, probably the expression of RCA plaque coronary vasospasm that cause the ECG shark fin sign and OHCA. This sign correlates with high risk of cardiogenic shock, electrical instability, and cardiac arrest, thus requiring prompt and aggressive management.