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Introduction[edit | edit source]


Cardioversion is the process of converting a heart that is in an abnormal and potentially dangerous rhythm into a normal sinus rhythm. Heart rates that are irregular or too fast are candidates for cardioversion. The most common procedures involve either medications (pharmacological cardioversion) or electricity (electrical cardioversion or defibrillation). Which method is used depends on the patient's condition and overall stability[1].

  • The normal heart rate comes from the sinoatrial node and progresses through the right atrium to the atrioventricular node and then through the conduction system to the ventricles.
  • For a variety of reasons (eg structural changes to the heart, medications, and tissue damage) the heart can develop a rhythm that does not follow the normal pattern and can lead to heart rates that are too fast, too slow, or are irregular[2].

Electrical Cardioversion[edit | edit source]

Medical illustration of an AED (Automated Eternal Defibrillator)

Electrical cardioversion is a procedure used to convert an abnormal heart rhythm (such as Atrial Fibrillation) to a normal rhythm (sinus rhythm). This is where an electrical shock is given over the chest. This electrical shock stops the abnormal rhythm of the heart for a brief moment and allows the normal heart rhythm to take over. It is applied to the anterior chest to stop a life-threatening or unstable tachycardic arrhythmia eg V Fib.[3] [4].

The direct current (DC) shocks to the heart has long been used successfully to convert abnormal heart rhythms back to normal rhythms[5].

Medical illustration of an AED

Synchronized & Unsynchronized Cardioversion

  1. In synchronized electrical cardioversion, the electrical discharge from the cardioversion machine is synchronized with the electrical activity of the patient’s heart. Appropriate synchronized electrical cardioversion restores the activity of the electrical conduction system of the heart and is the most effective resuscitation measure for many arrhythmias.[4] Synchronized electrical cardioversion may be scheduled (elective procedure) or done as an emergency procedure.[5]
  2. Unsynchronized cardioversion is not as "clever", uses more energy, and delivers a shock at any point during the cardiac cycle, when the machine has reached full charge. For all intents and purposes, unsynchronized cardioversion is the same thing as defibrillation or Automated external defibrillators (AEDs) , and is used when the patient does not have a pulse[6]. A defibrillator or AED can save someone's life if they have a cardiac arrest.[7]

Cardioversion is performed both inside and outside the hospital, and it is one technique that all healthcare professionals, eg nurses, physiotherapists, should be familiar with[4].

Automated External Defibrillators[edit | edit source]

AED in Amsterdam airport

Automated external defibrillators (AEDs) are designed to be user-friendly. Because they’re commonly kept in homes, offices, gyms and other locations devoid of trained medical personnel, they’re equipped with streamlined operations and easy-to-follow instructions.

An automated external defibrillator should only be used on someone suffering sudden cardiac arrest, presenting as unconscious and not breathing. It should never be used on a patient suffering a heart attack, who is still conscious and breathing. The person should be unresponsive without a palpable pulse, and no breathing or just gasping (in the case of agonal respirations).

  • Start by shouting their name and asking for a response, while gently shaking the victim.
  • Then check for signs of breathing.
  • Administer CPR and defibrillation only if they’re not breathing and unresponsive.
  • Follow the easy-to-follow instructions.

Chemical Cardioversion[edit | edit source]

Beta Blockers action

Chemical cardioversion involves treating with a medication to convert the rhythm back into a normal sinus rhythm. The success of the chemical cardioversion depends on many factors, including the underlying cause of the arrhythmia, and the duration of the arrhythmia.[2]

Conduction system.png

Pharmacological cardioversion does not require sedation. Electrical cardioversion is preferred in patients who are unstable ie they have a dangerously abnormal blood pressure or other symptoms. The classes of medications used for pharmacological cardioversion are specific to the condition being treated and include:

  1. Adenosine: Used for supraventricular tachycardia (SVT) that is not atrial fibrillation, adenosine is the newest of the pharmacological cardioversion agents. In the heart adenosine causes dilation of the coronary blood vessels that improves blood circulation to the heart. In the heart adenosine decreases heart rate
  2. Beta-Blockers: a class of drugs used to prevent the progression of heart failure and manage arrhythmias (irregular heart beat) and hypertension.
  3. Calcium Channel Blockers: Like beta-blockers, calcium channel blockers can either be used for acute cardioversion of supraventricular tachycardia in certain circumstances or be prescribed for chronic control of recurring tachycardia and hypertension.
  4. Atropine, dopamine, or epinephrine can be used in bradycardia for chemical cardioversion (an implanted pacemaker is a long term treatment of bradycardia)[8].

References[edit | edit source]

  1. Very well health What is cardioversion Available: 267.2.2022)
  2. 2.0 2.1 Goyal A, Hill J, Singhal M. Pharmacological Cardioversion. StatPearls [Internet]. 2021 Jul 31. Available: (accessed 27.2.2022)
  3. QLD health Cardioversion Available: 27.2.2022)
  4. 4.0 4.1 4.2 Goyal A, Sciammarella JC, Chhabra L, Singhal M. Synchronized electrical cardioversion. StatPearls [Internet]. 2020 Jul 31.Available: (accessed 27.2.2022)
  5. 5.0 5.1 Medicine Net What Is a Synchronized Electrical Cardioversion? Available: (accessed 27.2.2022)
  6. Avive Cardioversion Vs Defibrillation: Everything You Need to Know Available: 27.2.2022)
  7. Health direct Defibrillators Available: 27.2.2022)
  8. Very well health Cardioversion Available: (accessed 27.2.2022)