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External electrical cardioversion – consent information for patients

Read our guide below about the cardioversion procedure, also known as direct current cardioversion (DCCV).

This page will help you understand the procedure and help you prepare for it – please read it carefully.

You can also download a PDF version of this patient information by following the link on the right.

What is cardioversion?

Cardioversion is a day case procedure. It’s used to treat abnormal heart rhythms such as an irregular or fast heart rate like atrial fibrillation.

Your cardiologist has suggested this treatment for you.

What are the benefits?

Cardioversion restores a normal heart rhythm and relieve any symptoms associated with abnormal heart rhythms such as palpitations, breathlessness and tiredness. The hearts’ pumping function, called ejection fraction, may improve after establishing a normal heart rhythm .

You may also notice improvement in your ability to exercise.

Are there any risks?

Cardioversion successfully restores normal rhythm in about 90% of patients but it’s not a cure. It’s likely that the abnormal heart rhythm happens again.

Sometimes the abnormal heart rhythm may return within the first hours or days after the cardioversion. If this happens your specialist will discuss further treatment options at your next appointment.

Complications following the procedure

It’s rare that complications happen after a cardioversion. The most common complication is temporary skin redness or irritation in the area where we place sticky pads on your chest and back. Skin burn in this area is less common.

This may resolve without treatment or by using a simple skin cream, such as an unperfumed moisturizer.

Serious complications are very rare. These include:

  • a slow heart rhythm (bradycardia). Occasionally drugs help speed the heart up and in rare circumstances, temporary pacing. Very rarely a permanent pacemaker may treat this slow heart rhythm
  • a fast heart rhythm in the lower chambers of the heart (ventricular tachycardia or fibrillation) which may need further shocks whilst under general anesthetic
  • the risk of stroke (between 0.5% to 0.8%) as long as you have taken your blood-thinning medication correctly for 4 weeks before the cardioversion.

The risks of general anaesthetic are rare. We’ll discuss this with you on the day of the procedure.

Alternative treatment

Your doctors recommended cardioversion as the most appropriate treatment for your condition as they feel the benefits outweigh the risks. If you wish to discuss alternatives, please speak to your doctor or nurse.

Before the cardioversion

Your doctor may refer you for cardioversion treatment after seeing you in a clinic or after you attend our emergency departments. You’ll be placed on the waiting list.

Before we can book the procedure. you’ll need an ultrasound scan of the heart (echocardiogram) and sometimes a heart monitor that you wear for 24 hours. If required, we’ll arrange these tests for you.

You’ll also need take a blood thinner such as warfarin or an alternative drug.

If you take warfarin

You must have your warfarin level checked every week for 4 consecutive weeks before the cardioversion.

This test is also called INR, normally done as a finger prick blood test by your GP or warfarin clinic. These must be recorded in your yellow book (a record kept by each patient). If any of those results show an INR level less than 2, you must tell the cardioversion team.

If you take an alternative drug such as Apixaban, Dabigatran, Rivaroxaban or Edoxaban

You must take the medicine for a minimum of 4 weeks. Do not miss any dose.

It’s very important to follow these instructions to reduce the risk of stroke.

Some patients may need to take an additional drug called Amiodarone for 4 weeks before the cardioversion.  We’ll tell you if this applies to you.


We can now book your cardioversion and telephone pre-assessment. This is to make sure that you’re fit and prepared for the procedure. You can also ask any questions you have about the cardioversion treatment. Please have a list of your current medication available.

We’ll send you a letter confirming the date of your cardioversion.

The cardioversion can’t go ahead without the telephone pre-assessment.

We’ll also arrange for you to have blood tests and covid test before the cardioversion. This will happen a few days before your cardioversion,

If you take a drug called Digoxin, you must stop taking it 48hrs before your cardioversion.

Can I eat or drink before the procedure?

If you have a morning appointment, you must not eat from midnight. Take your morning medications with sips of water before 6am.

If you have an afternoon appointment, you can have breakfast with your morning medication before 8am. You should have nothing to eat after that but can have sips of water until 10am.

What happens when I arrive for my cardioversion?

On the day of the procedure, report to the Cardiac Day Unit, upper ground floor, Wycombe Hospital at the time stated on your letter.

We’ll ask you to change into a hospital gown and a nurse or doctor will prepare you for the procedure. They’ll ask you some questions, record an ECG (electrocardiogram – trace of the hearts’ electricity) and insert a cannula (small plastic tube) in your arm.

They’ll explain the benefits and risks of cardioversion, answer any questions you may have and ask you to sign a consent form.

You’ll then go to the theatre where the procedure takes place.

What happens during the cardioversion?

We do the cardioversion under a short general anesthetic so you will be asleep and not aware of the procedure. An anesthetic doctor will make sure you’re fit before you have the anesthetic.

While you’re asleep, normally for about 5 to 10 minutes, a nurse or doctor will do the cardioversion. They’ll place sticky pads on your chest and back connected to a defibrillator to deliver a controlled electrical shock across your heart. Normally, we can deliver the shock up to 3 times to try to restore the normal heart rhythm.

After the treatment, we’ll take you to recovery and monitor you until you’re fully awake.

After the cardioversion

When you’re completely awake, we’ll take you back to the Cardiac Day Unit where you can eat and drink. If you recover well, you can go home usually within a couple of hours. Before your discharge, we’ll take another ECG and remove your cannula. A nurse will then explain the result of the procedure and give you a discharge letter.

24 to 48 hours after the procedure

The general anesthetic takes some time to clear from your system. You must not drink alcohol, sign legally binding documents or make important decisions for 24 hours after the cardioversion.

You also can not drive for 48 hours following a general anesthetic. You must go home with a relative or friend and must have a responsible adult with you overnight. You should travel by car and not use public transport.

Follow up appointment and blood thinning medication

We’ll arrange an outpatient clinic appointment within 6 to 8 weeks. If your heart pumping function is affected, you’ll also have an echocardiogram.

You must continue to take the blood-thinning medication at least until we review you in clinic.

What should I do if I have any questions or feel unwell?

Contact the cardioversion team. If you feel unwell and need urgent care you should contact 111, your GP or 999.

Preparation checklist

Follow the steps below to help prepare you for your cardioversion

 Step 1  Read the information above or in the PDF carefully
 Step 2  Write down any questions to ask during your pre-assessment appointment
 Step 3  Arrange for someone to bring you to hospital and collect you after the cardioversion
 Step 4  Arrange for someone to stay at home with you overnight
 Step 5  Arrange some time off work if needed, especially the day after your cardioversion and if your work involves driving
 Step 6  If you take warfarin, arrange weekly INR (warfarin level) readings for 4 weeks before the cardioversion. Contact the cardioversion team if any of these are below 2.0
 Step 7  If you take one of the newer blood thinning medications (such as Apixaban, Dabigatran, Rivaroxaban or Edoxaban), take these without missing any doses for a minimum of 4 weeks
 Step 8  Attend the telephone pre-assessment appointment
 Step 9  Attend appointment for blood and covid tests
 Step 10  For patients on Digoxin, stop taking 48 hours before the procedure
 Step 11  Follow the rules for eating and drinking before the cardioversion

Useful links

The Healthy Rythm Alliance provides information about symptoms, conditions and a helpline.

About our patient information pages and leaflets

This patient advice is intended as general information only. We aim to make the information as up to date and accurate as possible, but please note that it is subject to change.

Always check specific advice on any concerns you may have with your doctor.

Contact us

Cardioversion nurse
Cardiac Day Unit
Bookings co-ordinators
Cardioversion nurse

Mondays and Thursdays, 9am to 11.30am

01494 323 411

Cardiac Day Unit

01494 425278

Bookings co-ordinators

01494 324175 or 01494 324464