Aortic Valve: Structure, Function & Diseases

The aortic valve is one of four heart valves or one of two so-called leaflet valves. It is located at the exit of the left ventricle into the aorta. The aortic valve opens during systolic contraction of the left ventricle and allows ejection of blood from the ventricle into the aorta, the beginning of the systemic circulation. During the subsequent diastolic relaxation phase of the left ventricle, the aortic valve closes and prevents the backflow of blood from the aorta into the ventricle.

What is the aortic valve?

The aortic valve is one of two so-called leaflet valves of the heart and is located at the exit of the left ventricle (chamber) to the aorta, the major artery of the body. The aortic valve opens during systolic contraction of the left ventricle, allowing blood to be pumped out of the ventricle into the aorta. Once blood pressure decreases toward the end of systole, there is a tendency for blood to flow back from the aorta into the left ventricle. A fully functional aortic valve prevents blood from flowing back because its “pockets” fill with blood and block the pathway from the aorta into the left ventricle. Instead, the left ventricle can refill with oxygenated blood from the left atrium. The aortic valve functions purely passively due to the different systolic and diastolic pressure and flow conditions in the heart. The valve does not have any muscles that could actively assist in opening and closing as is the case to some degree with the two leaflet valves, the mitral valve, and the tricuspid valve.

Anatomy and structure

The aortic valve is located in the left ventricle at the origin of the aorta, the large artery of the body. As a so-called pocket valve, the heart valve is composed of three crescent-shaped pockets formed by the intima, the innermost layer of blood vessels. The pockets are attached to a connective tissue-like ring, the annulus fobriosus, and are called the valvula semilunaris dextra, sinistra, and septalis. In exceptional cases, the aortic valve consists of only two leaflets. This is an embryonic maldevelopment or peculiarity that is created as early as the 5th to 7th week of pregnancy. The two-pocket aortic valve can also be fully functional. At the free end of each pocket, there is a small nodular thickening framed by the crescent-shaped valve leaflet. This anatomic feature supports the valve’s valvular function, which is entirely passive because there are no muscle cells or tendon filaments-as in the two leaflet valves-to support it.

Function and tasks

The main function of the aortic valve is to allow blood to flow from the left ventricle into the aorta, the body’s main artery, during the contraction phase of the ventricles (systole). This means that the aortic valve opens and offers as little resistance as possible to the flow of blood into the aorta to help the heart eject blood. If the outflow were only slightly obstructed, the heart would have to pump much harder, which could lead to damage to the heart muscle in the long run. The next main function of the aortic valve is to prevent blood from flowing from the aorta back into the left ventricle during the diastolic relaxation phase of the ventricles. This means that at the moment when the blood pressure in the ventricle decreases and becomes lower than that in the aorta, the aortic valve closes the aortic orifice, preventing blood from flowing back into the ventricle. This allows oxygenated blood to flow from the left atrium into the ventricle during diastole – provided that the mitral valve, the leaflet valve between the left atrium and left ventricle, opens properly and allows blood to flow from the left atrium into the left ventricle. If the aortic valve exhibits dysfunction in either of its two roles of opening and closing the aortic entrance at the proper time, the heart muscles must attempt to compensate for the reduced efficiency by increasing pumping power, which can lead to cardiac muscle overload in the long run.

Diseases

In principle, malfunction of the aortic valve is conceivable both in opening the aortic entrance and in closing the entrance at the proper time. Narrowing of the aortic valve or inadequate opening is referred to as aortic stenosis.If the aortic valve does not close properly and there is partial backflow of blood from the aorta into the left ventricle, valve insufficiency of a certain magnitude is present. Valve insufficiency and valve stenosis may occur separately or together as a so-called combined valve vitium. In rare cases, the changes in the aortic valve that lead to functional impairment are due to congenital valve defects, which is not always noticed early because the heart tries to compensate for valve stenosis or valve insufficiency by increasing its output. Malfunctions – especially of the aortic valve – are usually acquired. Typical triggers may include rheumatic fever or infectious endocarditis or myocarditis. Bacterial infections have also been observed, in the course of which the bacteria settled on the heart valves and led to changes in the valves. Survived endocarditis on the aortic valve can lead to scarring of the fine pockets, so that the valve can no longer close completely and grade I or II insufficiency develops. Gradually progressive degenerative changes in parts of the aortic valve, such as calcification, are also among the acquired valvular defects.

Typical and common heart diseases

  • Heart attack
  • Pericarditis
  • Heart failure
  • Atrial fibrillation
  • Heart muscle inflammation