cardioversion

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.

Ventricular tachycardia — A rapid heart beat, usually over 100 beats per minute.

Resources

Organizations

American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. <http://www.americanheart.org>.

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cardioversion /car·dio·ver·sion/ (-ver´zhun) the restoration of normal rhythm of the heart by electrical shock.

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car·di·o·ver·sion (kärd--vûrzhn)

n.

Restoration of the heartbeat to normal by electrical countershock or by use of medication.

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cardioversion

[-vur′zhən]

Etymology: Gk, kardia + L, vertere, to turn

the restoration of the heart's normal sinus rhythm through an electric shock delivered by a defibrillator. Application of the shock is synchronized to the QRS complex. Cardioversion is used to slow the heart or to restore the heart's normal sinus rhythm when drug therapy is ineffective at doing so. Cardioversion may also be done pharmacologically, with IV antiarrhythmic medication. Also called cardiovert.

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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.

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cardioversion

the delivery of a direct current shock synchronized with the qrs complex to the myocardium as an elective treatment to end tachydysrhythmias; called also countershock and precordial shock. Used in humans, it has also been effectively used in dogs with atrial fibrillation and ventricular tachycardias.

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cardioversion

Interventional cardiology The conversion of a cardiac arrhythmia, usually a tachyarrhythmia to a normal sinus rhythm; CV is most effective in terminating tachycardias due to defective reentry–eg, atrial flutter, A Fib, AV nodal entry, WPW syndrome, V tach with a pulse, flutter; the electric shock depolarizes all excitable myocardium, prolongs refractoriness, interrupts reentry circuits, and establishes electrical homogeneity; it is attempted in Pts with AFib in order to improve cardiac function, relieve symptoms, and ↓ risk of thrombus formation; transesophageal echocardiography identifies Pts with atrial emboli requiring short-term anticoagulation with heparin before cardioversion. See Chemical cardioversion, Direct current cardioversion, Single-pulse cardioversion. Cf Defibrillation.

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Patient discussion about cardioversion.

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Ince again,
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