Normal heart anatomy describes the four chambers of the heart and their connections to the veins and arteries. The upper two chambers of the heart are called the right and left atria. The atria are the receiving chambers for blood returning from the body and the lungs. The wall dividing the two atria is called the atrial septum. The lower two chambers are the right and left ventricles. The ventricles are muscular chambers responsible for pumping blood to the body and lungs. The wall dividing the two ventricles is called the ventricular septum. There are four separate valves in the heart: the tricuspid valve, pulmonary valve, mitral valve, and aortic valve. The valves open to allow blood to flow forward and close to prevent any backflow. Finally, there are a number of veins and arteries attaching to the heart. The superior and inferior vena connect to the right atrium, while the pulmonary veins connect to the left atrium. The pulmonary artery connects the right ventricle to the lungs, while the aorta connects the left ventricle to the body.

Coarctation of the aorta is a congenital heart defect, or a birth defect of the heart. It involves a narrowing of the aorta, the main blood vessel carrying oxygen-rich blood from the left ventricle of the heart to all of the organs of the body.  Coarctation occurs most commonly in a short segment of the aorta adjacent to the ductus arteriosus. The ductus arteriosus is a blood vessel normally present in all fetuses that forms a connection between the pulmonary artery and the aorta.  The ductus arteriosus has special oxygen-sensing tissue in its wall that causes it to close in the first hours or days of life. It is thought that coarctation may be caused by the presence of extra ductal tissue extending into the adjacent aorta which results in aortic narrowing as the ductal tissue contracts.

Junctional tachycardia (or junctional ectopic tachycardia or JET) is an arrhythmia, or an abnormal heart rhythm that causes a fast heart rate in children. Normal electrical conduction in the heart starts with the generation of electricity in the sinus node in the upper portion of the right atrium. Electricity moves from the sinus node through the atrium. From there, it is transmitted to the AV node to the ventricles. As electricity passes to the ventricles, the heart muscle contracts.

Every time the heart squeezes it requires an electrical impulse. With normal electrical conduction, impulses originate from an area in the top right corner of the heart known as the sinus node. Electricity then spreads across the upper two chambers of the heart. It travels to the lower two chambers through a specialized conducting pathway known as the >AV node. Normally the only way for electricity to travel from the upper to the lower chambers is through the AV node.

Sudden cardiac death refers to any process by which the heart suddenly stops beating. The vast majority of cases of sudden cardiac death occur in older adults who have pre-existing heart problems. For example, in older people who have had heart attacks, or myocardial infarctions, sudden cardiac death is often triggered by electrical disturbances related to the injured heart muscle.

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