Investigations

• blood count ^d
• urea and electrolytes, creatinine ^d
• glucose ^d
• cardiac enzymes ^b - see chest pain chapter for more details
• creatinine kinase ^a  
• 12-lead ECG looking for:
  • ischaemic changes ^a  
  • evidence of arrhythmias ^a

• EEG ^c  
• hyperventilation test: (at least 2 symptoms associated with episode reproduced ^c
• brain imaging ^d

• event recorders ^a  
• or Holter monitoring ^b  worn for at least 24 hours ^c  
• echocardiography ^c  
• investigating for a pulmonary embolism

• tilt table testing ^b  
• electrophysiologic studies ^b  
• signal-averaged ECG ^a  

Note

• A standardised work-up can find a cause in two-thirds of patients. ^b