What Is Cardioversion?

Introduction

Cardioversion is a popular medical technique used to restore arrhythmias, which are abnormal heart rhythms, to normality.¹ The use of cardioversion began in the mid-twentieth century and has since become a common medical procedure.^{2, 3} Cardioversion has become a mainstay therapy for atrial fibrillation, atrial flutter, and ventricular tachycardia.¹ There are two types of cardioversion, electrical and pharmacological, though both share the same aim, which is to normalise one’s heart rhythm.⁴ Cardioversion can carry several complications, including thromboembolisms, though these may be rare and more likely to affect the elderly, diabetics, and those with mitral valve regurgitation.^{5, 6}  Though cardioversion aims to normalise heart rhythm, it is not always successful in permanently restoring your heart rhythm to normal, which may warrant a second round of cardioversion or alternative therapy.⁷

Indications for cardioversion

Cardioversion is used to treat disorders characterised by an abnormal heart rhythm, which are known as arrhythmias. Atrial fibrillation, atrial flutter, and ventricular tachycardia are conditions commonly treated with cardioversion.¹

Atrial fibrillation

Atrial fibrillation is the most common type of arrhythmia. This condition results from abnormal electrical activity within the atria, which are the upper chambers of the heart, causing them to contract in an uncoordinated fashion. Atrial fibrillation can be, but is not always, persistent. Signs and symptoms do not always occur in atrial fibrillation but may include palpitations, chest pain, shortness of breath, and dizziness. The longer the condition persists, the higher the chance of complications, with stroke being the major complication of this condition, highlighting the importance of rapid treatment.⁸

Atrial flutter

Atrial flutter is the second-most common arrhythmia, following atrial fibrillation. Normally, when the heart contracts, every time there is a single contraction of the atria, there should be a single contraction of the heart’s lower chambers, the ventricles. However, in atrial flutter, there are several atrial contractions to one ventricular contraction. Similar to atrial fibrillation, signs and symptoms can be absent in the condition but may occur in certain cases. Symptoms that may occur include palpitations, lightheadedness, fatigue, and shortness of breath. If unaddressed, atrial flutter can lead to complications, including heart failure, cardiomyopathy, and stroke.⁹

Ventricular tachycardia

Ventricular tachycardia is characterised by the rapid beating of the ventricles, the lower chambers of the heart. Typically, ventricular tachycardia results from underlying heart disease, though other diseases can cause the condition too. There are a range of signs and symptoms that can result from ventricular tachycardia, including palpitations, chest pain, shortness of breath, syncope, and cardiac arrest. This condition can be life-threatening and is responsible for the majority of sudden deaths related to disorders of the heart. ¹⁰

Types of cardioversion

Electrical

Electrical cardioversion aims to restore an abnormal heart rhythm to normality using energy. Two paddles, known as electrodes, are applied to the chest and allow for the energy to be applied to the heart. The exact mechanism of how electrical cardioversion normalises heart rhythm is not known. Nonetheless, the energy applied in electric cardioversion results in an electric shock which stabilises the heart rhythm. Before the procedure begins, anaesthesia and sedatives are administered to reduce the pain felt during cardioversion.³

Pharmacological

Pharmacological cardioversion, also known as chemical cardioversion, involves the use of medication to convert an abnormal heart rhythm to a normal one. Many types of medication can be used for pharmacological cardioversion and the specific drug used may depend on what condition is specifically being treated.¹¹

Preparation for cardioversion

In preparing to undergo cardioversion, you typically will need to have been fasting for about eight hours beforehand. If you take medication, you should ask your physician whether you can take these before the procedure. Electrical cardioversion can be painful and, therefore, before it commences, anaesthesia and sedatives will be given so no pain can be felt.^{3 11 12}

Complications of cardioversion

Cardioversion is typically a safe procedure, carrying minimal complications. However. sometimes the therapy may cause complications:³

• Ventricular fibrillation
• Thromboembolisms
• Atrial arrhythmia
• Heart block
• Bradycardia
• Transient left bundle branch block
• Hypotension
• Pulmonary oedema
• Skin burns from the electrodes or paddles used in electric cardioversion

Whilst cardioversion can successfully facilitate the heart’s return to a normal rhythm in many cases, it can also be unsuccessful in many patients. Sometimes, this means a patient will undergo a second round of cardioversion and, in other cases, alternative therapies may be tried.⁷

Recovery after cardioversion

Following cardioversion, you typically will need to stay at the hospital for one to two days for monitoring until your heart rhythm normalises. During this period of monitoring, your heart rhythm and blood pressure will be routinely checked.¹¹ As cardioversion can increase the risk of thromboembolisms occurring, you may be asked to take anticoagulants for two weeks after the procedure to reduce the risk of thromboembolism occurring.¹³

Summary

Cardioversion is a medical therapy used to normalise an abnormal heart rhythm, such as in atrial fibrillation, atrial flutter, and ventricular tachycardia. Cardioversion can be administered through two means, either electrically or pharmacologically, both sharing the aim of establishing a normal heart rhythm. The success of this therapy can vary, with it being able to return an abnormal heart rhythm to normal in some, whereas other patients may have recurrent arrhythmias requiring a second round of cardioversion or alternative medical therapy. Complications of cardioversion are rare but are more likely to occur in the elderly, diabetics, and those with mitral valve regurgitation.

FAQs

What heart conditions can be treated with cardioversion?

Arrhythmias, disorders characterised by an abnormal heart rhythm, can be treated with cardioversion. Atrial fibrillation, atrial flutter, and ventricular tachycardia are commonly treated with this therapy.¹

How is electrical cardioversion performed?

Electrical cardioversion involves the use of paddles, known as electrodes, to apply energy to the heart. This application of energy causes an electric shock which leads to normalisation of the heart’s rhythm. The exact mechanism of how this normalisation of heart rhythm occurs is not known.³

What medications are used in pharmacological cardioversion?

A range of medications can be used in pharmacological cardioversion. The specific drug used depends on your specific underlying condition.¹¹

Is anaesthesia or sedation used in cardioversion?

Anaesthesia and sedation are used in electric cardioversion to minimise discomfort and pain during the procedure.³

How long does it take to recover from cardioversion?

It typically takes one to two days for the heart to return to a normal rhythm after cardioversion, during which heart rhythm and blood pressure will need to be monitored. 

Will I need to be hospitalised for cardioversion?

You likely will need to be hospitalised to undergo cardioversion, particularly as you will need to be monitored after, for one to two days, or until your heart rhythm normalises.¹¹

What are the success rates of cardioversion? 

The success rates of cardioversion can vary depending on a patient’s underlying condition, as well as factors such as age. Furthermore, the timing of the cardioversion taking place can impact how successful it is. Cardioversion tends to be most effective, with a success rate of 95%, when used within 12 to 48 hours of signs and symptoms of arrhythmia occurring. This success rate declines as more time passes.¹³

Are there any lifestyle changes I need to make after cardioversion to prevent abnormal heart rhythms in the future?

Certain lifestyle changes can reduce your risk of experiencing an arrhythmia. These lifestyle changes include being more physically active, quitting smoking, and dietary changes, particularly for prediabetics, diabetics, and obese patients.¹⁴

Can cardioversion be repeated if necessary?

Though cardioversion can be effective at normalising your heart rhythm, it can be unsuccessful in some cases. In cases where it is not initially successful, it can often be repeated. However, if it fails to work a second time, an alternative therapy will likely be trialled.⁷