Defibrillation

Defibrillation Electrode Position

Defibrillation is a treatment for life-threatening cardiac dysrhythmias, specifically ventricular fibrillation (VF) and non-perfusing ventricular tachycardia (VT).

Mechanism

A defibrillator delivers a dose of electric current (often called a counter-shock) to the heart. This process depolarizes a large amount of the heart muscle, ending the dysrhythmia. Consequently, the body's natural pacemaker in the sinoatrial node of the heart is able to re-establish normal sinus rhythm.

Types of Defibrillation

Defibrillators can be external, transvenous, or implanted (implantable cardioverter-defibrillator), depending on the type of device used or needed.

Some external units, known as automated external defibrillators (AEDs), automate the diagnosis of treatable rhythms, enabling lay responders or bystanders to use them effectively with little or no training.

Medical Uses

Defibrillation is often an important step in cardiopulmonary resuscitation (CPR).

Medical Uses

Defibrillation is often an important step in cardiopulmonary resuscitation (CPR). CPR is an algorithm-based intervention aimed to restore cardiac and pulmonary function.

Contraindications

If the heart has completely stopped, as in asystole or pulseless electrical activity (PEA), defibrillation is not indicated. Defibrillation is also not indicated if the patient is conscious or has a pulse. Improperly given electrical shocks can cause dangerous dysrhythmias, such as ventricular fibrillation.

Outcomes

Survival rates for out-of-hospital cardiac arrests are often less than 10%. Outcome for in-hospital cardiac arrests are higher at 20%.

See Also

• Cardioversion
• Automated external defibrillator
• Cardiac arrest

References

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