Transient triangular QRS-ST-T waveform with good outcome in a patient with left main coronary artery stenosis: A case report.

Triangular QRS-ST-T waveform, also known as "shark fin pattern", is an ECG presentation of ST segment elevation myocardial infarction with a unique wave composed by the QRS complex, the ST segment, and the T wave. It is associated with very poor prognosis and recently has been shown to be more common in patients with left main coronary artery (LMCA) involvement. Nevertheless, data supporting this correlation is scant. Herein we present a case of a patient with LMCA subtotal occlusion who developed a transient triangular QRS-ST-T waveform after an initial ECG had shown subendocardial ischemia. Electrocardiographic findings resolved spontaneously, and the patient was successfully treated without major complications. It is uncertain what caused the change between patterns.