Restoring Heart Rhythm with Defibrillation
Defibrillation is a procedure used to restore normal heart rhythm. Electrical charges are sent to the heart, usually from pads placed externally on the chest. The shock depolarizes the heart and can allow the heart to resume normal beating.
In the event of cardiac arrest (when the heart suddenly stops pumping blood effectively), defibrillation may be used. Cardiac arrest is often caused by a heart attack due to heart disease but can also result from other incidents such as choking, drowning or trauma.
If you have a heart attack, your heart is likely to be in a state of ventricular fibrillation where heart beats irregularly and cannot pump blood effectively.
The faster defibrillation is performed after cardiac arrest, the higher the chance that the heart will resume normal beating. If you are in the hospital when you experience cardiac arrest, defibrillation can be performed immediately. But for people who have heart attacks or cardiac arrest outside the hospital, getting access to a defibrillator will take more time. For this reason, there has been a push to make defibrillators available in public places so defibrillation can be administered quickly.
These portable machines, called automated external defibrillators (AEDs), are capable of analyzing the heart rhythm and delivering an electric shock to the heart, if necessary. Just as for CPR (cardiopulmonary resuscitation), training is available for use of AEDs by the general population.
While defibrillators come in various sizes and designs, the steps in defibrillation are basically the same. First, the heart rhythm is assessed to determine whether the heart will benefit from defibrillation. With AED, this step is performed automatically after electrode pads are placed on the chest. Then, the correct voltage is determined and an electric shock is delivered from the defibrillator to the heart through the pads or paddles on the chest.
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In addition to external defibrillators that are used to treat cardiac arrest, implantable defibrillators are available. These devices are inserted internally to maintain proper heart rhythm in patients who are at risk of ventricular defibrillation.