The cardiac septum separates the right side of the heart from the left side. A distinction can be made between a ventricular and an atrial septum.
What is the cardiac septum?
The cardiac septum is also known as the septum or cardiac septum in medical terminology. It separates the atrium and ventricle of the left heart from the atrium and ventricle of the right heart. While the right atrium and chamber are part of the so-called low-pressure system or small circulation, the left side of the heart with the left chamber and atrium belongs to the large systemic circulation. Defects in the cardiac septum are in the majority genetic. They can occur as isolated heart defects or in combination with other malformations and cause different symptoms depending on their localization. A rough distinction can be made between atrial septal defects and ventricular septal defects.
Anatomy and structure
The cardiac septum consists of an atrial septum and a ventricular septum. The atrial septum (septum interartriale cordis) has a fairly thin wall and is located between the right and left atria. On the posterior side of the heart, the septum becomes visible as the interatrial sulcus. On the anterior side, on the other hand, the interatrial sulcus is obscured by the aorta. The wall of the ventricular septum is thicker than the wall of the atrial septum. The ventricular septum separates the right ventricle from the left ventricle. In the ventricular region, the septum consists mainly of a thick muscular wall. This part is also called the pars muscularis. Towards the base of the heart, however, the wall becomes thinner and membranous. It is therefore also called the pars membranacea in this area. The pars membranacea houses an important part of the cardiac conduction system. The His bundle runs here before it then divides first into the Tawara legs and later into the Purkinje fibers. The ventricular septum runs along the outside of the heart through the interventricular sulcus anteriorly and posteriorly.
Function and Tasks
The interventricular septum separates the right side of the heart from the left side, ensuring that arterial and venous blood do not mix. Oxygen-depleted blood from the organs enters the right atrium via the body’s venous system. The blood then flows through the tricuspid valve into the right ventricle during diastole. During systole, the blood is ejected through the pulmonary valve into the pulmonary arteries. Gas exchange then occurs in the lungs. The blood, now rich in oxygen, passes through the pulmonary veins into the left atrium and through the mitral valve into the left ventricle. In systole, the aortic valve opens and the blood flows into the aorta. From there, it distributes throughout the body’s arterial vascular system, providing nutrients and oxygen to the organs.
Diseases
Defects of the cardiac septum are also called septal defects. Depending on the initial manifestation, a distinction can be made between congenital and acquired septal defects. The atrial septal defect belongs to the congenital malformations. It is therefore congenital. It is a malformation of the heart in which the cardiac septum between the two atria is not completely closed. About 10 percent of all congenital heart defects are ventricular septal defects. Ventricular septal defect is one of the shunt ventricular defects. All congenital heart defects in which there is a connection between the arterial and venous legs of the bloodstream are shunt ventricular defects. Depending on the direction of blood flow, a distinction can be made between right-to-left and left-to-right shunts. Symptoms of ventricular septal defect depend on the size of the shunt. The heart defect usually becomes noticeable between the ages of 2 and 20. Most patients with a ventricular septal defect suffer from cardiac arrhythmias and signs of heart failure. These include, for example, shortness of breath and reduced exercise capacity. Characteristically, patients with such a defect have a pale skin color. The extremities are often slightly bluish in color (peripheral cyanosis). In the case of a major defect, the first symptoms appear in infancy. Even later, children suffer from heart palpitations, reduced performance and shortness of breath on exertion. Ventricular septal defect is also usually congenital. Here, the cardiac septum between the two chambers of the heart is not fully developed. Like the atrial septal defect, the ventricular septal defect is also a shunt vitium.The defect is most commonly found in the membranous and less commonly in the muscular portion of the cardiac septum. Depending on the size of the defect, a left-to-right shunt may develop. In this case, blood flows from the left ventricle back into the right ventricle, resulting in a pressure load and a volume load on the right heart. The result is pulmonary hypertension. As more blood enters the pulmonary circulation, blood pressure within the pulmonary vessels increases. If this is the case, the shunt may reverse. Blood then flows from the right ventricle directly into the left ventricle. Like small atrial septal defects, small ventricular septal defects often go unnoticed. Larger defects eventually lead to left heart failure and result in increased lung infections. The atrioventricular septal defect is also a congenital malformation. In this malformation, the combination of an atrial septal defect and a ventricular septal defect creates an AV canal, resulting in the development of a double left-to-right shunt. The result is absolute volume overload with valvular insufficiency. The function of the heart deteriorates rapidly as the disease progresses. Eventually, the atrioventricular septal defect usually develops into complete heart failure.
