His ECG reading was normal. In about 20-30 per cent of cases, the first ECG may show up as normal even if one is having a heart attack. That’s why we need to conduct serial ECGs and test cardiac enzymes (which are biomarkers, such as troponin and creatinine, and indicate heart damage) over 12 to 24 hours, says Dr Saugata Chatterjee, assistant medical superintendent of Guru Gobind Singh (GG) General Hospital, Jamnagar