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Atrial Fibrillation (cont.)

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Converting atrial fibrillation (AFib) to a normal rhythm

Converting AFib 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 atrial fibrillation 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 try medical cardioversion first, and, if medications fail, then try electrical cardioversion.

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

  • patients younger than 65 years of age;
  • patients who have had AFib for a short time (less than 12 months);
  • patients with normal-sized atria and ventricles; and
  • patients who are having their first episode of AFib.

Cardioversion with medications

Before prescribing medications for cardioversion, the doctor usually controls the rate of ventricular contractions and thins the blood, usually with warfarin.

Available medications for cardioversion

Medications used in cardioversion usually work by blocking the channels in the walls of cells through which ions travel (sodium channels, potassium channels, beta adrenergic channels, and calcium channels). Some examples of these medications include:

  • Quinidine (Quinaglute) -- rarely used
  • Procainamide (Procan SR) -- rarely used
  • Disopyramide (Norpace) -- rarely used
  • Sotalol (Betapace)
  • Flecainide (Tambocor)
  • Amiodarone (Cordarone)

These medications are capable of converting AFib to normal rhythm in about 50% of patients. They often are used long term to maintain a normal rhythm and prevent recurrences of AFib.

Disadvantages of using medications for cardioversion

Medications used for converting atrial fibrillation carry a small risk of causing other abnormal heart rhythms -- they are said to be proarrhythmic -- especially in patients with diseases of the heart muscle or coronary arteries. These abnormal heart rhythms can be more life-threatening than atrial fibrillation. Therefore, treatment with these medications often is initiated in the hospital while the patient's rhythm is continuously monitored for 24 to 72 hours.

These medications may not be effective in the longer term. Many patients eventually develop a recurrence of atrial fibrillation despite the medications.

Medications used in treating atrial fibrillation often have important side effects. Many patients discontinue them because they cannot tolerate these side effects. For example, amiodarone is commonly used in treating atrial fibrillation because it is less proarrhythmic and has been shown to maintain a normal rhythm in up to 75% of patients. However, amiodarone may cause side effects and drug interactions. Amiodarone can interact with other medications such as tricyclic antidepressants, for example, amitriptyline (Elavil, Endep) or phenothiazine antipsychotics, for example, chlorpromazine (Thorazine), and cause abnormal heart rhythms. Amiodarone interacts with warfarin and increases the risk of bleeding. This interaction with warfarin can occur as early as 4 to 6 days after the start of both drugs or can be delayed by a few weeks. Thus, doctors prescribing both warfarin and amiodarone will adjust the dose of warfarin to avoid excessive blood thinning. Amiodarone also can cause thyroid disturbances in the fetus when administered orally to the mother during pregnancy. Amiodarone also may affect thyroid function in adults. The most severe side effect of amiodarone is lung toxicity that potentially can be fatal. Because of this lung toxicity, patients should report any symptoms of cough, fever, or painful breathing to their doctors.

Medically Reviewed by a Doctor on 5/4/2015

Source: MedicineNet.com
http://www.medicinenet.com/atrial_fibrillation/article.htm

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