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What is a Biphasic Defibrillator?

Jami Yontz
Jami Yontz

A biphasic defibrillator is a device used by medical professionals to reestablish a patient’s natural heartbeat using biphasic waveforms. Defibrillators are used when a patient with a life-threatening condition has an arrhythmia, such as ventricular fibrillation (V-fib). The shocks from a defibrillator will allow the heart to begin to contract naturally and pump blood, preventing death or cardiogenic shock.

Defibrillators are often used externally in conjunction with cardiopulmonary resuscitation (CPR) to revive a a patient. Portable units are available to emergency technicians, and many businesses and public buildings have a defibrillator on-site for use. A defibrillator usually has two metal handles that are placed over a person’s chest once a gel substance has been applied. There are also electrode pads available that are sticky and can be applied to a high-risk patient's chest so that a semi-automatic or automatic defibrillator can shock the patient out of cardiac arrest without the continual monitoring of a medical professional.


A biphasic defibrillator uses biphasic waveforms, which sends electrical currents from one paddle to the other and then transfers energy back to the original paddle. Uniphasic, or monophasic, defibrillators send one electric shock to the other paddle. Monophasic defibrillators may take several tries to shock the heart into returning to its normal rhythm, and requires an electrical current ranging from 200 joules to 360 joules. Biphasic defibrillator shocks require less energy because the electric currents are passed back and forth from the paddles over a longer period of time. 200 joules is the highest recommended energy level used with a biphasic device.

There are fewer risks associated with a biphasic defibrillator because of the lower amount of required energy. The repeated shocks sometimes necessary for patients can lead to post-resuscitation myocardial dysfunction, skin burns from the paddles, hemorrhage, edema, and damage to the tissues of the heart. Studies have shown that the more time the person spends in V-fib, the higher the amount of electricity and shocks needed to return to normal sinus rhythm will increase the risk of death or permanent damage.

Implantable biphasic defibrillators, known as an implantable cardioverterdefibrilator (ICD), are also available. Leads and a pulse generator are implanted into the person’s chest to monitor the heart for irregularities, including tachycardia and V-fib. Once an arrhythmia is detected, the device shocks the heart back to normal sinus rhythm. An ICD is only implanted in individuals who have an extensive history of heart attacks caused by ventricular arrhythmias.

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