Diagnosis and investigations

The criteria for diagnosing myocardial infarction are detection of rise and/or fall of cardiac biomarkers (preferably troponin) with at least one value above the 99th percentile of the upper reference limit, together with evidence of myocardial ischaemia with at least one of the following (1)

• symptoms of ischaemia
• electrocardiogram (ECG) changes indicative of new ischaemia (new ST-T changes or new left bundle branch block (LBBB))
• development of pathological Q wave changes in the ECG
• imaging evidence of new loss of viable myocardium or new regional wall motion abnormality

Notes:

• a chest radiograph may:
  • show heart failure
  • help to exclude aortic dissection
• laboratory investigations should include:
  • urea and electrolytes
  • full blood count
  • ESR
  • cardiac biomarkers (cardiac enzymes)

Reference:

• (1) NICE (March 2010). Assessment and diagnosis of recent onset chest pain or discomfort of suspected cardiac origin