A cardiac or heart defibrillator is a device that delivers an electric shock or pulse to the heart in order to alleviate certain disturbances or failures. Typically the goal is to change a fibrillation, or rapid and irregular rhythm, into a slower and steadier beat that can be managed by a care provider. The shock comes from an electric current that is channeled through the patient's chest via electrodes or paddles. The current causes the heart muscle to contract, hopefully jolting it back to a more natural pace.

When a person is experiencing cardiac arrest, the most common cause is ventricular fibrillation. Here, the ventricles are contracting in a chaotic fashion that causes the heart to stop pumping sufficient blood. The other form of fibrillation, atrial fibrillation, is more common and much less deadly. It is a disorder found in approximately two million Americans and causes the small upper chambers of the heart, or atria, to quiver rather than beat steadily. Though this isn't normally a life-threatening condition, atrial fibrillation can cause blood to pool and clot. If this clot becomes lodged in the brain or artery, a stroke can result.

In years past, the image of a cardiac defibrillator has been that of a last resort, life saving measure undertaken in an emergency room by doctors or surgeons. Although this is still often the setting in which they are used, recent years have seen heart defibrillators become increasing common in the general public for life saving measures.

Specifically, the automated external defibrillator has become a fixture in places such as airports, casinos and various sports arenas. When using the automated external defibrillator, the machine automatically determines whether a shock is needed and selects the appropriate level of energy. Therefore they are an effective tool for those not in the medical field who wish to keep a defibrillator on hand is case of a sudden cardiac attack.

Heart defibrillators have even become common in the home as a method of saving lives. Studies have shown that the vast majority of heart attacks or cardiac arrests occur within the home, but until recently the defibrillator was too bulky and cumbersome an apparatus to keep there. Now with portable cardiac defibrillators, family members have more methods for saving the life of a loved one than simple CPR.

The American Heart Association has sought to continue broadening access to and education on the use of cardiac defibrillators in hopes of helping regular citizens save the lives of victims of cardiac arrest when professional medical attention is unavailable. Though some experts have expressed concern over possible misuse or over-reliance on portable or automated defibrillators, it can surely be said that any device that promotes education and readiness for life saving measures among the general public can only be a good thing.