UW Health Services

•	Heart Services
•	Vascular Medicine

Cardioversion

Definition

Cardioversion is a method to restore a rapid heart beat back to normal. Cardioversion is used in persons who have heart rhythm problems (arrhythmias), which can cause the heart to beat too fast.

Information

Cardioversion can be done using electric shock (electric cardioversion) or medications (pharmacologic cardioversion).

ELECTRIC CARDIOVERSION

Electric cardioversion uses a device that can be placed inside (internal) or outside (external) the body.

An external cardioversion is often done during an emergency situation. External cardioversion uses a device called a defibrillator. When the defibrillator paddles are placed on your chest, a shock is delivered to your heart. This shock causes the heart rate to return to a normal rhythm.

People who have a recent arrhythmia (usually atrial fibrillation) or one that can not be controlled with medicines may be scheduled for external cardioversion. Before this is done, tests such as a transesophageal echocardiogram are often done to make sure that there are no blood clots in the heart. Some people may need to take blood thinners before the cardioversion procedure. If you are having a scheduled cardioversion, you will usually be given a sedative before the procedure starts.

After the procedure, you may be given medicine to prevent blood clots and help prevent the arrhythmia from coming back.

Internal cardioversion uses a device called an implantable cardioverter defibrillator (ICD). ICDs have two parts: a pulse generator and electrodes (wires). The generator is implanted under the skin, like a pacemaker. The wires connect the generator to the heart. If the heart starts beating incorrectly, the defibrillator will sense it and send an electrical shock to the heart, which returns the beat to normal. The generator battery usually lasts for 5 to 8 years.

An ICD is normally used for treating ventricular tachycardia or ventricular fibrillation. The severity of these arrhythmias can cause sudden death because of the dangerously fast heart rate. Less often, internal cardioversion is used to treat atrial (upper heart chamber) arrhythmias.

Before an internal defibrillator is used to perform internal cardioversion, your cardiologist or other health care provider will make sure the electric shock does not make your arrhythmia worse. Once set, the ICD works the same way an external defibrillator would.

PHARMACOLOGIC CARDIOVERSION

Cardioversion can be done using drugs that are taken by mouth or given through an intravenous line (IV). It can take several minutes to days for a successful cardioversion. If pharmacological cardioversion is done in a hospital, your heart rate will be regularly checked. Although rare, cardioversion using drugs can be done outside the hospital, but this requires close follow-up with a cardiologist.

As with electrical cardioversion, blood thinning medicines may be given to prevent blood clots from moving to the heart.

COMPLICATIONS

Possible complications of cardioversion are uncommon, but may include:

• Worsening of the arrhythmia
• Blood clots that can cause a stroke or other organ damage
• Bruising, burning, or pain where the paddles were used
• Allergic reactions from medicines used in pharmacologic cardioversion

Those who perform external cardioversion may be shocked if the procedure is not done correctly. This can cause heart rhythm problems, pain, even death.

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