Can you tell me how can a doctor know if a person has had a heart attack a few hours ago.?

4hrs. If the troponins are elevated you did. Takes 4 hrs from myocardial cell death for troponins to start rising. Therefore, troponins may still be negative early on. Clinical suspicion. Ecg may be undiagnostic over 60-70% of the times by itself. Many patients have stuttering mi's, in that case the troponin may be elevated from an event a few hours early that got reperfussed.Awakenbychestoppresion?Goer.