Defibrillation is a common treatment for life-threatening cardiac arrhythmia a, ventricular fibrillation, and pulseless ventricular tachycardia.

Defibrillation consists of delivering a therapeutic dose of electrical energy to the heart with a defibrillator.

Depolarize a a critical mass of the heart muscle, terminates the dysrhythmia, and allows normal sinus rhythm to be reestablished by the sinoatrial node of the heart.

Defibrillators can be external, transvenous, or implanted.

Automated external defibrillators (AEDs), automate the diagnosis of treatable rhythms, meaning that lay responders are able to use them successfully.

Biphasic defibrillation, alternates the direction of the pulses, completing one cycle in approximately 10 milliseconds, and significantly decreases the energy level necessary for successful defibrillation, decreasing the risk of burns and myocardial damage.

Ventricular fibrillation (VF) could be returned to normal sinus rhythm in 90% of cardiac arrest patients treated with a single shock from a biphasic defibrillator.

Implantable CDs do not require a thoracotomy and possess pacing, cardioversion, and defibrillation capabilities.

ICDs have inbuilt electrocardiogram readers, for which to diagnose arrhythmias which can be treated by different shocks.

Manual internal defibrillator provide charge is delivered through internal paddles in direct contact with the heart, and are almost exclusively found in operating rooms, where the chest is likely to be open, or can be opened quickly by a surgeon.

Automated external defibrillators (AED analyze the heart rhythm itself, and then advise the user whether a shock is required.

They are designed to deliver high joule shocks for VF (ventricular fibrillation) and VT (ventricular tachycardia) rhythms.

The automatic units are generally used by nonphysicians, while cardiac specialists generally employ manual defibrillators.

There are 2 types of AEDs: Fully Automated and Semi Automated.

Most AEDs are semi automated.

A semi automated AED automatically diagnoses heart rhythms and determines if a shock is necessary, and the user must then push a button to administer the shock.

Fully automated AED automatically diagnoses the heart rhythm and the shock is given automatically.

Almost half of patients with ventricular fibrillation remain refractory despite multiple defibrillation attempts.

Double sequential external defibrillation provides rapid sequential shocks from two different planes: anterior and lateral and anterior-posterior.

Vector change defibrillation switches defibrillation pads from anterior-lateral to the anterior-posterior positions offering a theoretical potential to defibrillate a portion of the ventricle that may not be completely defibrillated by pads in the standard anterior lateral position.

Among patients with refractory ventricular fibrillation survival to hospital discharge occurred more frequently in patients who received double sequential external defibrillation or vector change defibrillation than among those who received standard defibrillation (Cheskes S).

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