The septum of the heart is a wall of tissue that separates the left and right sides of the heart and enables blood to flow as it should. It consists of the atrial septum and the ventricular septum.

The atrial septum separates the left and right atria, while the ventricular septum separates the left and right ventricles.

The heart’s septum is critical for ensuring that blood flows properly through the heart.

If the septum does not form properly in the womb, it can result in a septal abnormality. These problems are relatively common and may resolve spontaneously. However, some abnormalities can cause serious health problems, such as stroke.

This article discusses the septum of the heart, its structure, and its function. It also covers septal abnormalities.

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The heart’s septum is a wall separating the right and left sides of the heart. The heart has two upper chambers called atria and two lower chambers called ventricles.

The heart’s septum comprises the atrial septum, which separates the atria, and the ventricular septum, which separates the ventricles.

A heart that develops typically should not have holes in the septum that allow blood to flow between the atria or ventricles. Instead, proper blood flow should only occur between the atria and ventricles.

However, some people are born with congenital heart abnormalities that can cause holes in the septum. These holes are called septal abnormalities. They can range from tiny to very large and can develop in different parts of the septum. They may often close on their own, but if they do not, people may require surgery.

A healthy septum is important for the proper functioning of the heart. The septum helps keep oxygen-rich blood from the lungs from mixing with oxygen-poor blood from the body.

It also prevents blood from flowing back into the heart chambers after pumping it out.

During cardiac cycle

  • Blood from the body enters the heart through two large veins called the superior and inferior vena cava. The blood initially enters the right atrium, and the atrial septum prevents it from entering the left atrium.
  • The heart then pumps the blood to the right ventricle, where the ventricular septum helps pump the blood to the lungs through the pulmonary artery.
  • Oxygen-rich blood from the lungs returns to the heart through the pulmonary vein and into the left atrium. Again, the atrial septum prevents blood from entering the right atria, and instead, the blood passes into the left ventricle.
  • The left ventricular septum helps generate the high pressure necessary to pump blood to the body through an artery called the aorta.

The septum sits in the center of the heart, between the right and left sides. It extends from the base of the heart to the apex, or tip.

The atrial septum is a thin, relatively mobile sheet of tissue between the two atria, just above the ventricles. In the womb, the atrial septum has an opening called the foramen ovale, which allows blood to bypass the lungs. After birth, this opening usually closes.

The ventricular septum is much thicker than the atrial septum. It is a triangular wall of cardiac tissue that consists of muscular and membranous portions. Its purpose is to prevent blood from flowing back into the ventricles after pumping it out.

What is the blood supply to the septum of the heart?

Certain coronary arteries supply blood to the heart and septum. These include the:

  • Left coronary artery: Supplies blood to the left side of the heart muscle, including the left ventricle and atrium.
  • Circumflex artery: Supplies blood to the lateral side and back of the heart.
  • Left anterior descending artery: Supplies blood to the front portion of the left ventricle and septum.
  • Right coronary artery: Supplies blood to the right atrium, the right ventricle, and the septum.

Various types of abnormalities can affect the heart septum.

Atrial septal defect (ASD)

These common septal abnormalities occur in around 1 in 4 children. They occur when the wall between the right and left atria fails to close.

There are five types of atrial septal abnormalities, depending on the location of the hole:

  • patent foramen ovale
  • ostium secundum defect
  • ostium primum defect
  • sinus venosus defect
  • coronary sinus defect

If an ASD is minor, it often closes on its own during childhood and may cause no symptoms. However, larger abnormalities that do not close spontaneously may need surgery to prevent complications, such as stroke or pulmonary hypertension.

Pulmonary hypertension occurs when small arteries in the lungs narrow, which ultimately leads to an increase in pulmonary pressure and can affect the right ventricle.

Ventricular septal defects (VSD)

A VSD is a hole in the wall separating the two ventricles. Doctors divide VSDs into types 1 to 4 depending on the location of the abnormality.

VSDs occur in around 0.3% of newborn babies. Around 90% of these abnormalities close by themselves, but if they do not, a person can experience pulmonary arterial hypertension and an increased risk of heart arrhythmias. Pulmonary arterial hypertension refers to high blood pressure in the pulmonary artery, which supplies blood from the heart to the lungs. A heart arrhythmia refers to an abnormality of the heart’s rhythm.

A baby may have an isolated VSD, or VSD can occur with other congenital heart abnormalities, such as an atrial septal abnormality.

Experts have identified several genetic factors that cause VSDs, but other factors may also play a role. For example, they may occur if the person carrying the fetus contracts an infection, rubella, or influenza. VSDs could also occur if a pregnant individual exposes the developing fetus to toxins, such as alcohol, cannabis, or certain medications.

Learn more about VSDs.

The septum is a wall of tissue separating the heart’s right and left sides. It consists of both atrial and ventricular septums. A healthy septum helps the heart pump blood efficiently by preventing it from flowing back into the heart chambers.

Various abnormalities can affect the septum, such as atrial septal defects and ventricular septal defects. These abnormalities are congenital, meaning they are present at birth. Septal abnormalities sometimes close on their own, but larger ones may require surgery.

Certain genetic factors can cause septal abnormalities, but there are also noninherited risk factors, such as exposure to certain infections or toxins.