The human heart beat is powered by chemical impulses produced by special cells called pacemaker cells. These cells are often affected by external stimuli– medication, stress, and physical activity, just a few things that change body chemistry; altering chemical impulses, increasing or decrease heartbeat. One of the most well-known and often misunderstood external heart stimuli is defibrillation.
Defibrillation is the administration of a jolt of electricity to the heart which depolarizes the heart muscle and allows the heart's natural pacemaker to potentially reset and continue beating. Defibrillation is performed by devices called defibrillators, which vary in design and ability. Currently, the familiar TV and movie trope of defibrillator paddles being used on flat-lining patients is outdated. More commonly, defibrillation will occur via the prophalayctic nodes, which are attached to the chest of the patient and also used to monitor heart rate. These nodes deliver shocks when a shockable heart rhythm occurs. Unlike TV shows, a shocked patient does not convulse, usually there is only a small amount of muscle contraction throughout the body. Also, unlike media portrayals, a flat line is usually an 'unshockable' rhythm. Ventricular fibrillation is a 'shockable' heart rhythm and is when the ventricles quiver rather than work in a pattern. Ventricular tachycardia, another shockable rythmn, is an extremely fast rhythm in which there is a loss of pulse. Certain types of cardiac arrhythmias may not be shockable depending on severity and rhythm type. Defibrillator devices in hospitals are usually not completely automatic, but are very similar to the completely automatic AEDs by Cardiac Science, Zoll, Phillips HeartStart, and Samaritan.
Click here for more information on automated external defibrillator
