Cardioversion vs Defibrillation
Both cardioversion and defibrillation involve delivering electrical energy to the chest to alter the heartbeat. Both are contraindicated in digoxin and catecholamine induced dysrhythmias. The techniques are similar in the two procedures. There are two paddle placements. In the antero-lateral placement method, one paddle goes on just right to the sternum on the upper chest while the other goes on at the mid-axillary line at the cardiac apex level. In the antero-posterior paddle placement method, the two paddles go on the front and the back of the chest. Both cardioversion and defibrillation can be biphasic and monophasic. Atrial arrhythmias are commonly seen as a side effect in both cardioversion and defibrillation. This article will try to explain the two procedures, the cardioversion and the defibrillation, in detail highlighting their types and usages.
Defibrillation is the delivery of a measured amount of electrical energy to the chest during any stage of the heart cycle. Defibrillation is a life-saving emergency treatment method for ventricular tachycardia and ventricular fibrillation. During a cardiorespiratory arrest, CPR and DC shock are the two methods available to restart the heart. There are five types of defibrillators. 1. Manual external defibrillator is almost exclusively found in hospitals or ambulances where a trained healthcare provider is available. It usually has a cardiac monitor to record cardiac electrical rhythm, as well. 2. Manual internal defibrillators are used in operating theaters, to restart the heart during an open thorax operation, and the leads are placed in direct contact with the heart. 3. Automatic external defibrillators need little training because it assesses the cardiac rhythm on its own and suggest the use of DC shock. It is mainly for use by untrained lay person. 4. Wearable cardiac defibrillator is a vest that can be worn, and it monitors the patient 24/7 and administers shock when needed.
Cardioversion is the delivery of a measured amount of electrical energy to the chest, synchronized with the large R wave of the electrocardiogram. The mechanism, technique, and equipment have the same basic operation principles as in defibrillation. There are specific cardioversion defibrillators that do not fire once the discharge button is pressed, and until the discharge is synchronized with an R wave in the ECG. Implantable cardioversion defibrillators recognize the need for shock and administer them as needed, synchronized with the large R wave.
What is the difference between Cardioversion and Defibrillation?
• Defibrillator is an emergency life-saving procedure done in ventricular tachycardia, ventricular fibrillation, and cardiac arrest while cardioversion is done to correct supraventricular tachycardia, ventricular reentrant tachycardia, atrial flutter and atrial fibrillation.
• Defibrillation is always done to restart the heart, so no anesthesia is needed. Cardioversion is done under sedation.
• Cardioversion may be done without anesthesia only if there is an imminent threat of cardiovascular collapse. Cardioversion may cause serious arrhythmias. There may be a transient elevation of ST segment after cardioversion.
• Pulmonary edema is also a known, rare complication of cardioversion. Defibrillation may cause myocardial necrosis rarely due to high energy shock delivery.