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DC cardioversion of atrial fibrillation

Last edited May 3, 2021

DC cardioversion requires a light general anaesthetic or sedation with intravenous diazepam; intubation is not usually required.

the DC shock is synchronized with an R wave on the electrocardiogram in order to reduce the chance of ventricular fibrillation
presence of two or more consecutive P waves after shock delivery is usually considered as an indication of successful DCC (1)

DC cardioversion may precipitate systemic emboli from intracardiac thrombus. To avoid thromboembolic events:

formal anticoagulation is required for at least three weeks before and four weeks after the cardioversion since
- thrombi may form as soon as 48 hours after the onset of AF(2)
- co-ordinated atrial activity may not resume for 2 weeks following cardioversion even if sinus rhythm is apparent on the ECG
prolonged anticoagulation is not needed when the arrhythmia has existed for less than 48 hours
- no intracardiac thrombus is apparent on trans-oesophageal echocardiography (3)

The use of DC cardioversion is

recommended acutely in patients who are haemodynamically unstable
considered electively in order to initiate a long-term rhythm control management strategy (1)

In patients who are haemodynamically stable and do not have severe underlying heart disease, outpatient/ambulatory DCC can be carried out (1)

The results of DC cardioversion in patients with chronic atrial fibrillation indicate a high initial effectiveness but poor long-term effectiveness:

70-90% patients with chronic atrial fibrillation will be converted to sinus rhythm by DC cardioversion
60-75% of successfully cardioverted patients will revert to atrial fibrillation within one year

NICE state with respect to cardioversion (6)

for people having cardioversion for atrial fibrillation that has persisted for longer than 48 hours, offer electrical (rather than pharmacological) cardioversion
consider amiodarone therapy starting 4 weeks before and continuing for up to 12 months after electrical cardioversion to maintain sinus rhythm, and discuss the benefits and risks of amiodarone with the person.
for people with atrial fibrillation of greater than 48 hours' duration, in whom elective cardioversion is indicated
- both transoesophageal echocardiography (TOE)-guided cardioversion and conventional cardioversion should be considered equally effective
- a TOE-guided cardioversion strategy should be considered:
  - where experienced staff and appropriate facilities are available and
  - where a minimal period of precardioversion anticoagulation is indicated due to the person's choice or bleeding risks
in people with atrial fibrillation in whom the duration of the arrhythmia is greater than 48 hours or uncertain and considered for long-term rhythm control, delay cardioversion until they have been maintained on therapeutic anticoagulation for a minimum of 3 weeks
- during this period offer rate control as appropriate

Notes:

DCC is contraindicated in patients with digitalis toxicity (1)
maintaining sinus rhythm after cardioversion
- several class IA, IC and III drugs are effective in maintaining sinus rhythm but increase adverse events, including pro-arrhythmia, and disopyramide and quinidine are associated with increased mortality. The authors of a systematic review concluded that (5) any benefit on clinically relevant outcomes (embolisms, heart failure, mortality) remains to be established

Reference:

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DC cardioversion of atrial fibrillation

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