electrical cardioversion in atrial fibrillation

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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:

Last edited 05/2021 and last reviewed 05/2021

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