MRCP-0134

A 54 yr. old heavy smoker presented with acute chest pain for 3 hrs which associated with excessive sweating and vomiting. His past medical history was unremarkable but his father has passed away due to a heart attack at the age of 50. Examination findings were normal and ECG was also normal. He was pain free after 12 hours from admission. What is the most appropriate investigation that cab be done at this moment?