A 22-year-old male university student presents to
casualty following an alcoholic binge. No previous medical history. On
examination he is in atrial fibrillation but there are no other abnormalities
detected. ECG confirms fast atrial fibrillation. No specific treatment is
given. He is transferred to a short stay ward where he sobers up repeat ECG
shows that he has reverted to sinus rhythm.
Which one of the following would be useful in this