Use an Automated External Defibrillator to Save a Life
Our hearts function as two-stage electrical pumps.

An electrical system that begins with the sinoatrial node located in the right upper chamber or atria of the heart coordinates the contraction of the chambers within the heart. Because the sinoatrial node cells do not have resting potential, the cells generate spontaneous action potentials that results in cell-to-cell conduction at a rate of 0.5 meters per second (m/sec).  In a normal heart, the cells within the sinoatrial node tissue generate an electrical stimulus 60 to 100 times per minute.

The slow depolarizing current travels to the atria and causes the cells within the atria to become less negative.  With this change, the atria switch on and contract for a short time as each cell transmits the electrical charge to the next cell.  In turn, the electrical current enters the ventricles through another special set of cells called the atrioventricular node.  With the conducting tissue slowing the conduction of the current to 0.05millisconds, the atrial can depolarize and contract before depolarization of the ventricles can occur.  

As the impulses enter the base of the ventricle, fibers that make up the left and right bundle branches conduct the impulses at rapid velocity of 2 m/sec.  As the branches divide, the electrical impulses move at rate of 4 m/sec through the ventricles. Given the electrical stimulation, the ventricles contract, generate pressure, and pump blood.

The synchronized pumping action of the atria and ventricles makes up the heart rhythm. A heart beat consists of one cycle of generated electrical signal and one heartbeat.  Whether we participate in strenuous physical activity or sleep, the electrical system regulates the heart rate to meet our body’s needs. 


Sudden cardiac arrest occurs because an interruption to the heart’s electrical circuit.  The condition happens within seconds without warning and causes an irregular heartbeat called arrhythmia.  Arrhythmia often occurs as a ventricular fibrillation or a rapid, unsynchronized heart rhythm that originates in the lower chambers of the heart.

Disrupting the pumping action of the heart stops the pumping of blood to the brain, lungs, and other areas of the body.  With this condition, an individual loses consciousness and the pulse rate drops to zero. Left untreated, an individual experiencing sudden cardiac arrest dies within minutes.  According to the National Safety Council, more than 320,000 out-of-hospital sudden cardiac arrests occur each year in the United States.  The NSC reports that:

  • Sudden cardiac arrest can happen to seemingly healthy individuals.
  • Sudden cardiac arrest causes more deaths than the combined number of deaths caused breast cancer, colon cancer, diabetes, and vehicle accidents.
  • Every minute of delay in treating sudden cardiac arrest reduces the chances for survival by ten percent.


An automated external defibrillator generates and delivers an electrical shock to the heart that can stop arrhythmia.  Stopping arrhythmia allows a normal heart rhythm to start.

Automated external defibrillators function around a computer and adhesive electrodes.  With the electrodes fastened to the patient’s chest, the AED computer can analyze the patient’s heart rhythm and check for ventricular fibrillation or pulseless ventricular tachycardia.  If the computer does not detect those conditions, the AED does not deliver an electrical shock. 

If ventricular fibrillation has occurred, the electrodes provide a biphasic electrical path for delivering an exact amount of current that shocks the heart back to its natural rhythm.  The biphasic electrical path allows current to travel from one electrode to the other and back in the other direction.  Biphasic shock uses less energy to restore the normal heart rhythm.  With less energy required, the design reduces the chance for burns to the skin or damage to the cells within the heart.

The portability, programming, and design of an AED allows anyone outside the medical profession to respond to a sudden cardiac arrest emergency.  When many brands of automated external defibrillators detect a life-threatening heart condition, audible prompts guide even a novice user through the process of applying the shock.  Cardio-pulmonary resuscitation (CPR) combined with the use of an AED increases the chances for survival by 75 percent.


Motion Industries encourages businesses and corporations to provide safety training that includes instruction in CPR and the use of an AED.  The National Safety Council offers courses designed to train the general public about using AEDs and how to perform CPR. Having access to an AED and the proper training saves lives.

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