Cardioversion
Definition
Cardioversion refers to the process of restoring the heart's normal rhythm by applying a controlled electric shock to the exterior of the chest.
Purpose
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 normal rhythm and pump more efficiently.
Precautions
Not all unusual heart rhythms (called
arrhythmias) are dangerous or fatal. Atrial fibrillation and atrial flutter often revert to normal rhythms without the need for cardioversion. Healthcare providers may also try to correct the heart rhythm with medication or recommend a lifestyle change before trying cardioversion. However,
ventricular tachycardia lasting more than 30 seconds and
ventricular fibrillation require immediate cardioversion.
Description
Elective cardioversion is usually scheduled ahead of time. After arriving at the hospital, an intravenous (IV) catheter will be placed in the arm and oxygen will be given through a face mask. A short-acting general anesthetic will be administered through the vein. During the two or three minutes of anesthesia, the doctor will apply two paddles to the exterior of the chest and administer the electric shock. It may be necessary to give the shock two or three times to obtain normal rhythm.
Preparation
Medication to thin the blood is usually given for at least three weeks before elective cardioversion. Food intake should be stopped eight hours before the procedure.
Aftercare
Medical personnel will monitor the heart rhythm for a few hours, after which the patient is usually sent home. It is advisable to arrange for transportation home, because drowsiness may last several hours. The doctor may prescribe anti-arrhythmic medication to prevent the abnormal rhythm from returning.
Risks
Cardioverters have been in use for many years and the risks are few. Those unlikely risks that remain include those instances when the device delivers greater or lesser power than expected or when power setting and control knobs are not set correctly. Unfortunately, in a number of cases, the heart prefers its abnormal rhythm and reverts to it despite cardioversion.
Normal results
Most cardioversions are successful and, at least for a time, restore the normal heart rhythm.
Key terms
Atrial fibrillation — A condition in which the upper chamber of the heart quivers instead of pumping in an organized way.
Atrial flutter — A rapid pulsation of the upper chamber of the heart that interferes with normal function.
Ventricular fibrillation — A condition in which the lower chamber of the heart quivers instead of pumping in an organized way.
Resources
Organizations
American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. <http://www.americanheart.org>.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
cardioversion
[kahr´de-o-ver″zhun] the delivery of a direct current
countershock synchronized with the QRS complex to the myocardium as an elective treatment to end
tachydysrhythmias. (For emergency treatment using a nonsynchronized current to terminate arrhythmia, see
defibrillation.) The goal of cardioversion is to restore sinoatrial control of the heart rhythm by depolarizing the entire myocardium at the moment of shock. The depolarization interrupts
reentry circuits, thus ending myocardial
fibrillation and some other types of
dysrhythmias. The electric shock can be delivered directly to the myocardium in an open chest procedure, or through externally applied paddles placed on the chest.
Cardioversion is most effective in terminating arrhythmias due to continuous
reentry, including
atrial flutter,
atrial fibrillation,
paroxysmal supraventricular tachycardia,
ventricular tachycardia, and
ventricular fibrillation. Patients who have had a recent myocardial infarction and resultant atrial, nodal, or ventricular tachycardia are the most frequent candidates for cardioversion. Those with severe, longstanding arrhythmias due to chronic extensive heart disease usually do not benefit from this procedure.
Cardioversion should be done only by trained physicians in a setting where resuscitation equipment and respiratory support are readily at hand. Serum
potassium levels must be within normal limits at the time of procedure because
hypokalemia increases the patient's chance of developing deadly postconversion
dysrhythmias. If necessary, potassium salts can be given prior to the procedure.
digitalis toxicity predisposes the patient to life-threatening
dysrhythmiasduring cardioversion and the drug should be withheld several days prior to the anticipated procedure.
hypoxia and
acidosis may decrease the chances of successful cardioversion.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
Patient discussion about cardioversion
Q. Does anyone know if its possible to get breast implants if i have an implanted defibrillator? I have hypertrophic cardiomyopathy. I'm 27 and in great health, I workout 6 days a week and I have no further symptoms.
A. Thanks for your help. In fact I have an appointment with my cardiologist in a couple of weeks and if he says its OOK I will definitely consult it with the plastic surgeon as well. However I always try to do some additional research on my own and get second opinions.
Ince again,
Thanks!
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