In a healthy person with a normal, in condition heart, it is unlikely that a sustained rhythm disturbance can occur without any external factor affecting. It may be an electric shock or use of any illegal drug. This is primarily because the heart is free from abnormal items, such as. Scar tissue. Scars in the heart may occur as a result of a wide range of conditions, but most commonly it is after a heart attack. Scar may interfere with initiation of an impulse in the sinus node or the spread of the impulse conduction system. In addition, the cardiac cells' inability to conduct electric impulses in the refractory period, helping to prevent accidental electrical impulses occurred elsewhere than in the sinus node, progresses to an arrhythmia. If, however, a heart disease or damage, initiation and propagation of the heart's electrical impulses become destabilized, which increases the risk of arrhythmias may occur.
Relaxation and electric charge
Each cell in the heart that contribute to the prevalence of the heart's electrical impulses, has two electric states: a charged (polarized) state and a relaxed (flat, refractory state) condition. In the polarized state, the heart cells are prepared and able to conduct the electrical impulse that will cause a heartbeat. After a heartbeat's cells in a flat phase, before they can be charged to a polarized state and is ready for a new heart. In the drained phase is the heart cells are unable to conduct an impulse.