Arrhythmia reliably known to be of less than 48h duration:

• Moderate to high-risk patients: these patients have a CHA₂DS₂-VASc score ≥1 and should have IV heparin, LMWH or a licensed DOAC commenced before DCCV and continued long term.
• Lower risk patients: CHA₂DS₂-VASc score = 0; as well as patients with very high bleeding risk do not require anticoagulation prior to DCCV. It is unclear whether four weeks of anticoagulation should be given post successful DCCV in this group.

Arrhythmia of uncertain duration or more than 48h duration:

• Oral anticoagulation (warfarin with INR >2.0 for three weeks and on the day of DCCV, or licensed NOAC) should be given for at least three weeks before, and continued for at least one month after cardioversion.
• Alternatively, a TOE-guided approach can be considered in those anticoagulated for less than three weeks pre-DCCV. A short period of anticoagulation is administered: LMWH or unfractionated heparin (bolus + infusion for APTT 1.5–2.0 times control) plus simultaneous PO warfarin initiation; or at least four doses dabigatran 150 mg bd or apixaban 5 mg bd without any heparin; or five days of warfarin pre-TOE with INR 2.0–3.0 on procedure day. TOE can then guide DCCV after excluding thrombus in left and right atrium, their appendages, and the LV. Post-procedural anticoagulation is continued for at least one month.
• INR, international normalized ratio.

Plasma potassium

• Check this is >3.5 mmol/L. Correct hypokalaemia before cardioversion (Chapter 86)

Digoxin

• Check that there are no features to suggest toxicity (nausea, slow ventricular response, frequent ventricular extrasystoles) and that if the dose is high (>250 μgm/day), renal function is normal.

Thyroid function

• Check that thyroid function is normal: cardioversion of atrial fibrillation due to thyrotoxicosis (which may be otherwise occult) is unlikely to be successful.

Tachybrady syndrome

• Consider placing a temporary pacing lead or having an external pacing system on stand-by,
• as asystole or severe bradycardia may follow DC cardioversion.

Nil by mouth

• Water up to 2h before anaesthesia.
• Food and other drinks up to 6h before anaesthesia.