Cardioversion

What is a Cardioversion procedure?

Cardioversion is a procedure that aims to restore the heart’s normal rhythm from an abnormal rhythm using high energy shocks. Most cardioversions are performed to treat certain types of irregular heartbeats (arrhythmias), including Atrial Fibrillation (AFib). 

Normally, each heartbeat starts in the upper right chamber (right atrium) of the heart in a region containing specialised pacemaker cells. Each time these cells fire, usually 1 to 2 times per second, they send an organised electrical signal through the heart that results in a coordinated, rhythmic heartbeat.

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In patients with arrhythmias however, such as atrial fibrillation, instead of the normal organised electrical activity, the atria ‘fibrillate’, or quiver, because of chaotic electrical wavefronts that circulate throughout both atria. This can result in less efficient blood pumping and an irregular or fast heartbeat. It can cause symptoms such as fainting, shortness of breath, dizziness and fatigue, and in severe cases can potentially lead to serious consequences such as stroke, heart attack, and even sudden cardiac death.

Depending on your specific medical history and symptoms, your cardiologist may recommend a cardioversion to return your heart to a normal rhythm. During an electrical cardioversion, a high-energy shock is sent to the heart which ‘upsets’ the abnormal signalling and lets the heart reset itself back into a normal rhythm.

Note, it is different from chemical cardioversion, in which medicines are used to try to restore a normal rhythm.

What is the difference between defibrillation and cardioversion?

Cardioversion is not the same as defibrillation. Both use shocks to reset the heart. But defibrillation uses a stronger shock to stop very severe rhythms that can cause sudden death, mostly in severe medical or emergency situations. Cardioversions are typically performed as a scheduled procedure.

How to prepare for a Cardioversion procedure

You will be admitted to a hospital for your Cardioversion procedure and you will be required to fast for at least six hours prior to the procedure.

Follow your cardiologist’s instructions about what medicines to take before the procedure. This includes any medicines to prevent abnormal rhythms. Don’t stop taking any medicine unless your healthcare provider tells you to do so. You might need blood tests before the procedure to make sure the procedure is safe to do.
If you are at higher risk of blood clots, your healthcare provider may want you to take anti-clotting medicine for several weeks before and after the procedure.
Do not apply any lotions or ointments to your chest before your procedure as it may interfere with the adhesiveness of the shocking pads.

What happens during a Cardioversion procedure

A cardiologist will be performing the Cardioversion, assisted by an anaesthetist and nursing staff. An IV line (drip) will be placed in your arm and medications given to put you into a light sleep for the entire procedure. Your throat will also be sprayed with an anaesthetic that will numb your gag reflex – this is to allow your Cardiologist also perform a Transesophageal Echocardiogram before your Cardioversion if required. Your electrocardiogram, oxygen saturation and other vital signs will be monitored during and after the procedure. The procedure typically only takes a few minutes.

During a Cardioversion, a synchronised electrical current or shock is delivered through the chest wall to the heart through special electrodes or paddles that are applied to the skin of the right upper chest and left lower chest. The purpose of the Cardioversion is to interrupt the abnormal electrical circuits in the heart and to restore a normal heartbeat. The delivered shock causes all the heart cells to contract simultaneously, thereby interrupting and terminating the abnormal electrical rhythm without damaging the heart. The heart’s electrical system then restores a normal heartbeat.

What happens after a Cardioversion procedure

You will remain in hospital for approximately three hours after the Cardioversion and will not be allowed to eat or drink for an hour or two, or until your gag reflex returns.

For several hours after the procedure you may feel sleepy and have a dry throat. As a result of the nature of some of the medications you may not be able to remember much of the Cardioversion procedure. You will need to have someone to take you home after the procedure as you are unable to drive for 12 hours post procedure. Many people need to take an anti-clotting medicine like warfarin or another blood thinner.

Cardioversion Frequently Asked Questions

Cardioversion is a safe and effective procedure and serious complications are rare. However, like any medical procedure, there are some risks associated with cardioversion.

Complications associated with cardioversion are:

Skin irritation and burns: The electric shock used during cardioversion can cause skin irritation or burns. Modern gel-based electrodes significantly reduce this risk compared to older electrode paddles.

Blood clots (Thromboembolism): Blood clots can be dislodged from the heart and into the blood stream during cardioversion. The blood clots can then travel along arteries, causing blockages and so it is possible for a cardioversion to cause a stroke. Anticoagulant medications commenced before cardioversion significantly reduce this risk. The risk of stroke from thromboembolism in a patient who is on anticoagulant medication before cardioversion is less than 1%.

Heart damage: In rare cases, cardioversion can cause damage to the heart muscle. This is usually a temporary issue and the heart function tends to recover quickly over a few days.

Anaesthesia risks: The anaesthetic given for cardioversion is usually given intravenously (in the vein) and is very short acting. It wears off quickly. Anaesthetic complications occur very rarely and can include including allergic reactions, breathing problems complications.

The recovery time after a cardioversion procedure is usually very quick.

The anaesthetic given for the cardioversion is usually intravenous (in the vein) and is very short acting: It works quickly and and wears off quickly.
Patients are kept in hospital under observation for a few hours post procedure and are allowed to eat and drink.

Most people are able to discharge from hospital 2-3 hours post cardioversion.

You should not drive a vehicle for 24 hours post procedure to allow enough time for the anaesthetic to be fully gone from your body.

It’s important to follow your doctor’s instructions carefully after the procedure and attend any follow-up appointments to monitor your heart rhythm.

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