Making a diagnosis in ACS

• when diagnosing MI, use the universal definition of myocardial infarction . This is the 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:
  • symptoms of ischaemia
  • ECG changes indicative of new ischaemia (new ST-T changes or new LBBB)
  • development of pathological Q wave changes in the ECG
  • imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
    
    
• the clinical classification of MI includes:
  • Type 1: spontaneous MI related to ischaemia due to a primary coronary event such as plaque erosion and/or rupture, fissuring or dissection
  • Type 2: MI secondary to ischaemia due to either increased oxygen demand or decreased supply, such as coronary spasm, coronary embolism, anaemia, arrhythmias, hypertension, or hypotension
    
    
• when a raised troponin level is detected in people with a suspected ACS, reassess to exclude other causes for raised troponin (for example, myocarditis, aortic dissection or pulmonary embolism) before confirming the diagnosis of ACS
  
  
• when a raised troponin level is detected in people with a suspected ACS, follow the appropriate guidance for unstable angina/ STEMI) until a firm diagnosis is made. Continue to monitor
  
  
• when a diagnosis of ACS is confirmed, follow the appropriate guidance (for unstable angina/NSTEMI or STEMI)
  
  
• reassess people with chest pain without raised troponin levels (determined from appropriately timed samples) and no acute resting 12-lead ECG changes to determine whether their chest pain is likely to be cardiac
  • if myocardial ischaemia is suspected, follow the recommendations on stable chest pain in this guideline Use clinical judgement to decide on the timing of any further diagnostic investigations
    
    
• consider a chest X-ray to help exclude complications of ACS such as pulmonary oedema, or other diagnoses such as pneumothorax or pneumonia
  
  
• only consider early chest computed tomography (CT) to rule out other diagnoses such as pulmonary embolism or aortic dissection, not to diagnose ACS
  
  

Reference:

• 1) NICE (March 2010). Chest pain of recent onset.