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Atrial Fibrillation (AF, AFib)

What is electrical cardioversion?

Other methods of converting AFib to a normal rhythm include electrical cardioversion and rate control therapy.

Electrical cardioversion is a procedure used by doctors to convert an abnormal rhythm (such as AFib) to a normal rhythm (sinus rhythm). Electrical cardioversion requires the administration of an electrical shock over the chest. This electrical shock stops the abnormal electrical activity of the heart for a brief moment and allows the normal rhythm to take over. Although electrical cardioversion can be used to treat almost any abnormal fast heartbeat (such as atrial flutter and ventricular tachycardia), it is used most frequently to convert atrial fibrillation to a normal rhythm.

Warfarin usually is given for 3 to 4 weeks prior to cardioversion to minimize the risk of stroke that can occur during or shortly after cardioversion. Warfarin is continued for 4 to 6 weeks after successful cardioversion. For some patients requiring urgent electrical cardioversion, warfarin may not work fast enough to thin the blood. Therefore, these patients may be given heparin prior to electrical cardioversion. Heparin is a faster-acting blood thinner than warfarin, but it must be administered as a continuous intravenous infusion or as injections under the skin. After successful cardioversion, these patients can be switched from heparin to warfarin.

Method of cardioversion

  • Electrical cardioversions (urgent and elective) usually are performed in a hospital. For elective (nonurgent) electrical cardioversion, patients usually arrive at the hospital without eating in the morning. Necessary medications can be taken with small sips of water. Patients are given supplemental oxygen via nasal catheters, and an intravenous infusion of fluids is started. Electrodes (pads) are placed on the skin over the chest to continuously monitor the heart rhythm. Paddles then are placed over the chest and the upper back. Patients are sedated (anesthetized) intravenously with medications. This is followed by a strong electric shock through the paddles. The shock converts the atrial fibrillation to a normal rhythm. After cardioversion, patients are observed for several hours or overnight to make sure that their normal heart rhythm is stable.

Effectiveness of electrical cardioversion

  • Electrical cardioversion is more effective than medications alone in terminating atrial fibrillation and restoring a normal rhythm. Electrical cardioversion successfully restores a normal rhythm in over 95% of patients.

Limitations of electrical cardioversion

  • While electrical cardioversion is effective in converting AFib to a normal heart rhythm, the normal rhythm may not continue for long. Approximately 75% of patients successfully treated with electrical cardioversion experience a recurrence of atrial fibrillation within 12 to 24 months. Older patients with enlarged atria and ventricles who have had atrial fibrillation for a long time are especially prone to recurrences. Thus, most patients who undergo successful cardioversion are placed on oral medications to prevent recurrences of the arrhythmia.

Risks and candidates for electrical cardioversion

What are the risks of electrical cardioversion?

The risks of electrical cardioversion include stroke, burns of the skin, and in rare instances, death. However, these complications are very uncommon.

Who are candidates for electrical cardioversion?

Doctors usually recommend that all patients with chronic, sustained AF undergo at least one attempt at cardioversion. Cardioversion usually is attempted with medications first. If medications fail, electrical cardioversion can be considered. Sometimes a doctor may choose to use electrical cardioversion first if AFib is of short duration (onset within 48 hours) and the transesophageal echocardiography shows no blood clots in the atria.

Electrical cardioversion is performed urgently (on an emergency basis) on patients with severe and potentially life-threatening symptoms caused by AFib. For example, some patients with rapid AFib can develop chest pain, shortness of breath, and dizziness or fainting. Chest pains in these individuals are due to an insufficient supply of blood to the heart muscles. Shortness of breath indicates ineffective pumping of blood by the ventricles. Fainting or dizziness usually is due to dangerously low blood pressure.

What is rate control therapy?

Recent studies have shown that an acceptable alternative to cardioversion (chemical or electrical) is rate-control therapy. In this therapy, the doctor will leave the individuals in AFib provided their rate of ventricular contractions is under good control, the output of blood from the heart is adequate, and their blood is adequately thinned by warfarin to prevent strokes. The rate in these patients can be controlled using medications such as beta blockers, calcium channel blockers, or digoxin or AV node ablation with pacemaker implantation. Rate-control therapy is used to simplify therapy and avoid the side effects of anti-arrhythmic medications (medications used to treat and prevent atrial fibrillation).

Over long periods of observation, individuals treated with rate-control therapy had similar survival and quality of life as compared to those who undergo repeated electrical or chemical cardioversions.

Suitable candidates for rate-control therapy include:

  • Patients who have had atrial fibrillation for more than one year
  • Patients with significant disease of the heart valves
  • Patients with enlarged hearts as a result of heart failure or cardiomyopathy (heart muscle weakness)
  • Patients with significant or intolerable side effects with medications for atrial fibrillation

Newer medications to prevent stroke

Newer antithrombotidc medial agents that are as effective as warfarin in preventing strokes in patients with atrial fibrillation that do not require such intense monitoring or dietary restrictions include:

  • rivaroxaban (Xarelto)
  • apixaban (Eliquis)
  • dabigatran (Pradaxa)

These antithrombotic agents work by a different mechanism from warfarin, and are suitable for many, but not all, patients. Indications should be discussed with the patient's doctor.

Converting (AFib to a normal rhythm (cardioversion)

Converting to a normal rhythm can be accomplished with medications (chemical cardioversion) or by electrical shocks (electrical cardioversion). Doctors usually recommend that all patients with chronic sustained Afib undergo at least one attempt at cardioversion, chemical or electrical. Successful cardioversion can alleviate symptoms, improve exercise tolerance, improve quality of life, and lower the risk of strokes. Doctors usually attempt medical cardioversion first, and, if medications fail, then try electrical cardioversion.

Patients who are more likely to attain and maintain a normal rhythm with either chemical or electrical cardioversion include patients:

  • Younger than 65 years of age
  • Who have had the disease for a short time (less than 12 months)
  • With normal-sized atria and ventricles
  • Who are having their first episode of AF
Reviewed on 1/30/2017
Atrial Fibrillation Quiz

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