DC cardioversion is a treatment by which a pulse of electricity is passed across the heart in order to convert an abnormal rhythm into the normal (sinus) rhythm.
It is carried out under general anaesthetic and requires you to be nil by mouth for 6 hours beforehand. It is usually done as a day case procedure and usually takes around 10 minutes.
When carried out for atrial fibrillation or atrial flutter, one normally needs therapeutic levels of blood thinning (anticoagulation) for at least 3 weeks beforehand.
If there has been a lapse in blood thinning (if the INR has dipped below 2 in the preceding 3 weeks if you are taking warfarin, or if you have omitted a dose of another anticoagulant) then it is often possible to go ahead, but a trans-oesophageal echocardiogram (ultrasound scan from the gullet) may be needed using a small probe to make sure that there is no evidence of blood clot within the heart.
DC cardioversion is often not a long term solution, and AF or atrial flutter may recur. If restoration of sinus rhythm resulted in improvement in quality of life but the rhythm disturbance recurs then catheter ablation can be considered.