EXTERNAL CARDIOVERSION

We generally perform cardioversion on patients with atrial fibrillation (most commonly) who are aware that they are in the abnormal rhythm and feel symptomatic. The typical symptoms they may have are palpitations, tiredness, lethargy and breathlessness on exertion. We sometimes perform cardioversion in patients with more vague symptoms such as tiredness and lethargy in an effort to put the heart back into normal rhythm and see if they feel better once normal rhythm is restored. 

Often if cardioversion works for a few weeks but atrial fibrillation then returns we would then have a potential mandate to think about pulmonary vein isolation (AF ablation) to cure the AF on a more permanent basis. Cardioversion can also be performed if patients have gone into atrial fibrillation or atrial flutter because of a recent illness such as a chest infection.

The most common complication is skin irritation and a minor skin burn where the defibrillator patches have been attached.  This is often caused by the electrical current going through the defibrillator pads (the sticky pads placed on your chest wall).  If there is any irritation or problem after the cardioversion please make the nurse aware and we can give you a cream called “Flamazine” which can improve the symptoms.  The most serious complication is a potential stroke following cardioversion.  

The risk of this is thought to be less than 1/100.  The risk is kept to a bare minimum by adhering strictly to your anticoagulation protocol.  If you are on warfarin then your INR (blood thinness level) should ideally be maintained at above 2 and below 3 for at least 4 weeks before the procedure.  If you are one of the newer anticoagulant agents (such as Rivaroxaban or Apixaban or Dabigatran) then it is vitally important you do not miss a single dose in the 4 weeks prior to the cardioversion procedure.  It is also equally important to continue to take the blood thinning medication after the cardioversion.

Patients are brought into the hospital an hour or two before the cardioversion is planned.  A cannula (drip) is put into one of your arms to allow the anaesthetist to give you the intravenous agent which is the general anaesthetic.  You will have been nil by mouth for the prerequisite time beforehand.  The nurses will check you in and go through a series of questions on the ward.  You will then be given a brief anaesthetic during which a shock will be delivered across the heart.  

You will not feel this as you will be asleep under anaesthetic.  We would generally try up to three (or maximally four times) to try and restart the heart back into normal rhythm.  If the procedure does not work after this number of shocks we would not continue to try.  The anaesthetic normally wears off between 5 and 10 minutes after it has been given and will be monitored closely by the nurse and the anaesthetist in the immediate aftermath of the anaesthetic and transferred back to the general ward.  

Once you are fully awake you can eat and drink and will generally monitor you for around 2 hours after the anaesthetic and then you can go home.  It’s important someone brings you to hospital as you will not be allowed to drive for at least 24 hours after the anaesthetic has worn off.

The immediate success of the procedure is around 80-90%.  That is to say 10-20% of patient will not be able to have their rhythm restored back to normal.  We then have the test of time.  Over the weeks and months to come some patients do slip back into atrial fibrillation/flutter and an important part of how we manage them in the long term is whether or not they are aware they have gone back into atrial fibrillation/flutter.  

If patients do notice a decline in their general well being and this is associated strongly with the recurrence of atrial fibrillation it is in these patients we generally consider potential ablation (Pulmonary vein isolation or PVI) moving forward.  After the first 12 months following cardioversion between 50 and 60% of patients will still have a normal heart rhythm.  It is vitally important you continue to take your blood thinning medication (warfarin or newer anticoagulants such as Apixaban and Rivaroxaban). 

Never stop the anticoagulants unless your cardiologist tells you to.  We would generally review patients between 4 and 8 weeks after a cardioversion to see how they are and often we would perform a heart monitor to see if the rhythm is stable throughout a 24 or 48 hour monitoring period.  The heart monitor is performed as an outpatient.