What is cardioversion?
An arrhythmia refers to any abnormal heart rhythm. Arrhythmias are typically divided into slow heart rhythms (bradycardia) and fast heart rhythms (tachycardia). Treatment for most forms of symptomatic bradycardia involves speeding up the heart rate. On the other hand, treatment for most forms of tachycardia involves slowing the heart rate, or preferably converting it back to a normal heart rhythm. This process is known as cardioversion.
Cardioversion can be achieved in many different ways. Most commonly it is done through the use of medications or by applying an electrical current to the heart. In children, cardioversion is most commonly used for the treatment of supraventricular tachycardia (SVT). In SVT, an electrical circuit is formed between the atria and ventricles. The circuit typically involves the AV node. Adenosine is a medication that transiently blocks conduction through the AV node. Giving adenosine is one form of medical cardioversion; it is typically very successful in terminating SVT. Cardioversion for SVT can also be accomplished by vagal maneuvers. With vagal maneuvers, a child performs one of a number of different bodily maneuvers (squatting down, blowing into an occluded straw, etc.) to activate the vagus nerve. The vagus nerve transiently blocks conduction through the AV node and can also cardiovert SVT.
What is electrical cardioversion?
Less common forms of tachycardia in children may not involve the AV node. These include atrial flutter, atrial fibrillation and ventricular tachycardia. These types of arrhythmias may not respond well to medical cardioversion and instead may require electrical cardioversion. Electrical cardioversion refers to the process of applying an electrical current to the heart to shock and subsequently reset the electricity in the heart.
When possible, electrical cardioversion is carried out in a controlled setting. Ideally it should be conducted in an intensive care setting where emergency personnel are immediately available. Usually intravenous medication is used to minimize pain and allow for sedation. Once this has been administered, specialized pads or paddles are applied to the child's chest in close proximity to the heart. The proper amount of electricity is selected on the machine and the device is set to synchronize with the patient's heart rhythm when appropriate. An electrical shock is then administered. When effective, the arrhythmia will instantaneously terminate and the sinus node typically takes over again.
In summary, cardioversion refers to the process of terminating an abnormal heart rhythm, either by the use of medication or electricity.