A 36-year-old woman presented with a 3-month history of recurrent substernal chest pain, which acutely worsened 2 days prior to presentation. Her initial troponin I was mildly elevated and ECG showed subtle changes initially concerning for ischaemia; however, these were present on her prior ECG and were not considered an acute change. Because of her age and lack of significant risk factors, she was considered low risk for cardiac disease and initially treated conservatively for a non-ST elevation myocardial infarction. Due to persistent symptoms and dynamic changes on ECG concerning for ischaemia, she was immediately taken for a cardiac catheterisation and was found to have critical left main coronary artery dissection with a focal stenotic lesion. She had an extensive workup to identify the underlying cause of her coronary artery dissection which was unrevealing. She underwent an uncomplicated coronary artery bypass graft surgery and was discharged home in stable condition.