Hypertrophy is called an enlargement of the heart muscle and heart size in response to excessive load caused by pressure or volume or trophic messages (such as hyperthyroidism). The extent of hypertrophy differs according to the underlying cause. Cardiac events from the onset of a beat up to the onset of the next beat are called cardiac cycle. Each heart cycle begins with spontaneous production of a potential for action in the sinusoidal node. This node is located in the upper outer wall of the right atrium and near the peritoneal vein of the corpus and the potential for action is rapidly transmitted from the atria and passes through the ventricular ventricle (AV) to the ventricles. Due to the specific order of the conduction device from the corridors to the ventricles, the cardiac impulse passes from the corridors to the ventricle with more than 0.1 seconds delayed. In this case, the atria will allow the ventricles to contracture and pump blood into the ventricles before the very contraction. Cardiac cycle consists of a rest period called diastole, in which the heart is filled with blood, followed by a period of contraction called systole.