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  1. What are the indications for cardioversion?

  2. What is the difference between cardioversion and defibrillation?

  3. What is the difference between monophasic and biphasic cardioverter-defibrillators?

  4. How much energy should be used during cardioversion?

  5. What are the indications for anticoagulation prior to cardioversion?

Cardioversion is a medical procedure whereby an abnormal heart rhythm (ie, cardiac arrhythmia) is converted back to a normal rhythm using electricity or drugs. Electrical cardioversion, also referred to as direct-current or DC cardioversion, involves the delivery of a synchronized (perfectly timed) electrical shock through the chest wall to the heart to terminate arrhythmias and restore sinus rhythm. Electrical cardioversion is an effective, rapid, and safe technique that has become a routine procedure in the management of patients with cardiac arrhythmias. Pharmacologic cardioversion, also called chemical cardioversion, uses antiarrhythmic medication instead of an electrical shock to restore the heart's normal rhythm.

Investigators at Johns Hopkins Hospital were the first to develop techniques of defibrillation by an electrical shock in the 1930s. The first human defibrillation was performed in the operating room by Claude Beck in 1947, and Paul Zoll introduced defibrillation using alternating current in 1956. Direct-current defibrillation was subsequently pioneered and introduced into clinical practice by Bernard Lown in 1962. Subsequent studies in the early 1960s demonstrated that electrical cardioversion across the closed chest could abolish other cardiac arrhythmias in addition to ventricular fibrillation (VF). Today, atrial fibrillation (AF) is the most frequent arrhythmia encountered in clinical practice and the most commonly cardioverted arrhythmia.

Distinguish Cardioversion and Defibrillation

Electrical cardioversion and defibrillation procedures both use a device (eg, cardioverter-defibrillator) to deliver an electrical shock to the heart to treat abnormal heart rhythms, but they differ in the timing of the shock and energy provided. Electrical cardioversion delivers energy synchronized (ie, perfectly timed) to the QRS complex and is used to treat arrhythmias such as AF, atrial flutter (AFL), or ventricular tachycardia (VT) with a pulse. Cardioversion can be performed electively (ie, nonemergently) in stable patients or emergently in situations to correct a rapid abnormal rhythm associated with faintness, low blood pressure, chest pain, difficulty breathing, or loss of consciousness. Cardioversion is not performed in pulseless patients.

Defibrillation delivers nonsynchronized (ie, occurs at random timing) energy during the cardiac cycle and is used to treat life-threatening arrhythmias such as pulseless VT or VF. Defibrillation is the treatment of choice for the arrhythmias most commonly associated with sudden cardiac arrest. The electrical shock delivered during cardioversion or defibrillation can be delivered externally to the heart using electrodes (external pads or paddles) placed on the chest (most common); directly to the heart using internal paddles during an open chest surgery; or through the electrodes of a permanently implanted cardioverter-defibrillator (ICD).

Mechanism of Cardioversion

Cardioversion disrupts the abnormal electrical circuit(s) in the heart and restores a normal heartbeat. The shock causes all the heart cells ...

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