Cardioversion refers to the process of restoring the heart's normal rhythm by applying a controlled electric shock to the exterior of the chest. Abnormal heart rhythms are called arrhythmias or dysrhythmias.
When the heart beats too fast, blood no longer circulates effectively in the body. Cardioversion is used to stop this abnormal beating so that the heart can begin its normal rhythm and pump more efficiently.
Cardioversion is used to treat many types of fast and/or irregular heart rhythms. Most often, cardioversion is used to treat atrial fibrillation or atrial flutter. Life-saving cardioversion can be used to treat ventricular tachycardia and ventricular fibrillation.
Abnormal heart rhythms are slightly more common in men than in women and the prevalence of abnormal heart rhythms, especially atrial fibrillation, increases with age. Atrial fibrillation is relatively uncommon in people under age 20.
Elective cardioversion is usually scheduled ahead of time. After arriving at the hospital, an intravenous (IV) catheter will be placed in the arm to deliver medications and fluids. Oxygen may be given through a face mask.
In some people, a test called a transesophageal echocardiogram (TEE) may need to be performed before the cardioversion to make sure there are no blood clots in the heart.
A short-acting general anesthetic will be given through the IV to put the patient to sleep. During the five or 10 minutes of anesthesia, an electric shock is delivered through paddles or patches placed on the exterior of the chest and sometimes on the back. It may be necessary for the doctor to administer the shock two or three times to stop the abnormal heartbeat and allow the heart to resume a normal rhythm. During the procedure, the patient's breathing, blood pressure, and heart rhythm are continuously monitored.
A doctor may be able to detect an irregular heart beat during a physical exam by taking the patient's pulse. In addition, the diagnosis may be based upon the presence of certain symptoms, including:
Not everyone with abnormal heart rhythms will experience symptoms, so the condition may be discovered upon examination for another medical condition.
DIAGNOSTIC TESTS. Tests used to diagnose an abnormal heart rhythm or determine its cause include:
EATING AND DRINKING GUIDELINES. The patient should not eat or drink anything for six to eight hours before the procedure.
OTHER GUIDELINES. It is advisable to arrange for transportation home, because drowsiness may last several hours and driving is not permitted after the procedure.
Do not apply any lotion or ointments to your chest or back before the procedure.
The patient generally wakes quickly after the procedure. Medical personnel will monitor the patient's heart rhythm for a few hours, after which the patient is usually sent home. The patient should not drive home; driving is not permitted for 24 hours after the procedure.
The doctor may prescribe anti-arrhythmic medications (such as beta-blockers, digitalis, or calcium channel blockers) to prevent the abnormal heart rhythm from returning.
Some patients may be prescribed anticoagulant medication, such as warfarin and aspirin , to reduce the risk of blood clots.
The medications prescribed may be adjusted over time to determine the best dosage and type of medication so the abnormal heart rhythm is adequately controlled.
Some chest wall discomfort may be present for a few days after the procedure. The doctor may recommend that the patient take an over-the-counter pain reliever such as ibuprofen to relieve discomfort. Skin irritation may also be present after the procedure. Skin lotion or ointment can be used to relieve irritation.
Cardioverters have been in use for many years and the risks are few. The unlikely risks that remain include those instances when the device delivers greater or lesser power than expected or when the power setting and control knobs are not set correctly. Unfortunately, in about 50% of cases, the heart prefers its abnormal rhythm and reverts to it within one year, despite cardioversion. Cardioversion can be repeated for some patients whose abnormal heart rhythm returns.
About 90% of cardioversions are successful and, at least for a time, restore the normal heart rhythm safely and prevent further symptoms.
The 2002 Rate Control vs. Electrical Cardioversion for Persistent Atrial Fibrillation (RACE) study, published in The New England Journal of Medicine indicated that controlling a patient's heart rate is as important as controlling the patient's heart rhythm to prevent death and complications from cardiovascular causes. The study also concluded that anticoagulant therapy is important to reduce the risk of stroke and is appropriate therapy for patients who have recurring, persistent atrial fibrillation even after they were treated with cardioversion. In patients who did not receive anticoagulant therapy after cardioversion, there was a 2.4% increase of embolic events (such as stroke or blood clots), even though there were no signs of these events prior to the procedure.
Atrial fibrillation and atrial flutter often revert to normal rhythms without the need for cardioversion. Healthcare providers usually try to correct the heart rhythm with medication or recommend lifestyle changes before recommending cardioversion.
Lifestyle changes often recommended to treat abnormal heart rhythms include:
If cardioversion is not successful in restoring the normal heart rhythm, other treatments for abnormal heart rhythms include:
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American College of Cardiology. Heart House. 9111 Old Georgetown Rd., Bethesda, MD 20814-1699. (800) 253-4636 ext. 694 or (301) 897-5400. http://www.acc.org .
American Heart Association. 7272 Greenville Ave. Dallas, TX 75231. (800) 242-8721 or (214) 373-6300. http://www.americanheart.org .
The Cleveland Clinic Heart Center, The Cleveland Clinic Foundation. 9500 Euclid Avenue, F25, Cleveland, Ohio, 44195. (800) 223-2273 ext. 46697 or (216) 444-6697. http://www.clevelandclinic.org/heartcenter .
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National Heart, Lung and Blood Institute. National Institutes of Health. Building 1. 1 Center Dr., Bethesda, MD 20892. E-mail: NHLBIinfo@rover.nhlbi. http://www.nhlbi.nih.gov .
North American Society of Pacing and Electrophysiology. 6 Strathmore Rd., Natick, MA 01760-2499. (508) 647-0100. http://www.naspe.org .
Dorothy Elinor Stonely Angela M. Costello
Heart doctors (cardiologists) specially trained in cardioversion (called electrophysiologists) should perform this procedure. To find a heart rhythm specialist or an electrophysiologist, patients can contact the North American Society of Pacing and Electrophysiology. Cardioversion usually takes place in the hospital setting in a special lab called the electrophysiology (EP) laboratory. It may also be performed in an intensive care unit , recovery room or other special procedure room.