Aortic valve

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Aortic valve
Diagram of the human heart (cropped).svg
Frontal view of the aortic valve
Gray497.png
Aortic valve
Details
Identifiers
Latin valva aortae
MeSH D001021
TA98 A12.1.04.012
TA2 3993
FMA 7236
Anatomical terminology

The aortic valve is a valve in the heart of humans and most other animals, located between the left ventricle and the aorta. It is one of the four valves of the heart and one of the two semilunar valves, the other being the pulmonary valve. The aortic valve normally has three cusps or leaflets, although in 1–2% of the population it is found to congenitally have two leaflets. [1] The aortic valve is the last structure in the heart the blood travels through before stopping the flow through the systemic circulation. [1]

Contents

Structure

The aortic valve normally has three cusps however there is some discrepancy in their naming. [2] They may be called the left coronary, right coronary and non-coronary cusp. [2] Some sources also advocate they be named as a left, right and posterior cusp. [3] [4] Anatomists have traditionally named them the left posterior (origin of left coronary), anterior (origin of the right coronary) and right posterior. [2]

The three cusps, when the valve is closed, contain a sinus called an aortic sinus or sinus of Valsalva. In two of these cusps, the origin of the coronary arteries are found. The width of the sinuses in cross-section is wider than the left ventricular outflow tract as well as wider than the ascending aorta. The junction of the sinuses with the aorta is called the sinotubular junction. The aortic valve is located posterior to the pulmonary valve and the commissure where the anterior two cusps join together points toward the pulmonary valve. It is these two sinuses that contain the origin of the coronary arteries. In the congenital disease known as transposition of the great arteries, these two valves are reversed (the anterior valve is the aortic valve) and the origin of the coronaries still follows this "rule" that the origins are in the sinuses facing the pulmonary valve.

Orifices of the Heart seen from above in An academic physiology and hygiene (1903).jpg

The term "semilunar" refers to an approximate half-moon shape of the valve leaflets. [5]

Function

Video clip from the aortic valve in a living, beating pig heart. Aortic valve.gif
Video clip from the aortic valve in a living, beating pig heart.

When the left ventricle contracts (systole), pressure rises in the left ventricle. When the pressure in the left ventricle rises above the pressure in the aorta, the aortic valve opens, allowing blood to exit the left ventricle into the aorta. When ventricular systole ends, pressure in the left ventricle rapidly drops. When the pressure in the left ventricle decreases, the momentum of the vortex at the outlet of the valve forces the aortic valve to close. The closure of the aortic valve contributes the A2 component of the second heart sound (S2). [6]

Insufficiency

Closure of the aortic valve permits maintaining high pressures in the systemic circulation while reducing pressure in the left ventricle to permit blood flow from the lungs to fill the left ventricle. Abrupt loss of function of the aortic valve results in acute aortic regurgitation (also known as acute aortic insufficiency) and loss in the normal diastolic blood pressure resulting in a wide pulse pressure and bounding pulses. The endocardium perfuses during diastole and so acute aortic regurgitation can reduce perfusion of the heart. Consequently, heart failure and pulmonary edema can develop.

Slowly worsening aortic insufficiency results in a chronic aortic regurgitation which permits the heart to compensate (unlike acute aortic regurgitataion). This compensation is through dilation of the left ventricle and return to normal filling pressures.

Stenosis

Inadequate opening of the aortic valve, often through calcific aortic valve disease, results in higher flow velocities through the valve and larger pressure gradients. Diagnosis of aortic stenosis is contingent upon quantification of this gradient. This condition also results in hypertrophy of the left ventricle.

Clinical significance

Micrograph demonstrating thickening of the spongiosa layer (blue) in myxomatous degeneration of the aortic valve. Myxomatous aortic valve.jpg
Micrograph demonstrating thickening of the spongiosa layer (blue) in myxomatous degeneration of the aortic valve.

A normally functioning valve permits normal physiology and dysfunction of the valve results in left ventricular hypertrophy and heart failure. Dysfunctional aortic valves often present as heart failure by non-specific symptoms such as fatigue, low energy, and shortness of breath with exertion. Common causes of aortic regurgitation include vasodilation of the aorta, previous rheumatic fever, infection such as infective endocarditis, degeneration of the aortic valve, and Marfan's syndrome. Aortic stenosis can also be caused by rheumatic fever and degenerative calcification. [7] The most common congenital heart defect is the bicuspid aortic valve (fusion of two cusps together) commonly found in Turner syndrome. Once diagnosed, the two options are to repair or replace the valve.

Aortic valve repair

Aortic valve repair or aortic valve reconstruction describes the reconstruction of both form and function of the native and dysfunctioning aortic valve. Most frequently it is applied for the treatment of aortic regurgitation. It can also become necessary for the treatment of aortic aneurysm, or less frequently for congenital aortic stenosis. [8]

Aortic valve replacement

Replacement of the aortic valve is done by replacing the native valve with a prosthetic valve. Traditionally, this has been a surgical procedure (surgical AVR or SAVR) but a non-surgical option called transcatheter aortic valve replacement (TAVR) or TAVI transcatheter aortic valve implantation delivers a prosthetic valve through a catheter. [9] The choice between SAVR and TAVR often relies on the open-heart surgical risk and indications for other open heart surgeries (etc., coronary bypass, other valve dysfunction). The Bentall procedure is a type of surgical procedure when the aortic valve, aortic root, and ascending aorta are replaced in a single operation.

There are two basic types of artificial heart valve: mechanical and tissue.

There are alternatives to animal tissue valves. In some cases, a human aortic valve can be implanted. These are called homografts. Homograft valves are donated by patients and recovered after the patient expires. The durability of homograft valves is probably the same as for porcine tissue valves. Another procedure for aortic valve replacement is the Ross procedure (after Donald Ross) or pulmonary autograft. The Ross procedure involves going to surgery to have the aortic valve removed and replacing it with the patient's own pulmonary valve. A pulmonary homograft (a pulmonary valve taken from a cadaver) or a valvular prothesis is then used to replace the patient's own pulmonary valve.

The first minimally invasive aortic valve surgery took place at the Cleveland Clinic in 1996.

Endocarditis

Endocarditis is infection of the heart and this often results in vegetations growing on valves. While it is possible for it to affect the aortic valve, it is not the most likely spot.

Evaluation

Evaluation of the aortic valve can be done with several modalities. Auscultation with a stethoscope is quick and easy. It contributes the A2 component to the second heart sound and changes with inspiration ("splitting") Transthoracic echocardiography (TTE) is used as the first test because it is non-invasive. Using TTE, the degree of stenosis and insufficiency can be quantified to grade the valve dysfunction. Transesophageal echocardiography is less often used for aortic stenosis & insufficiency because the angle between the probe and the aortic valve is not optimal (the best window is a transgastric view). MRI and CT can be used to evaluate the valve, but much less commonly than TTE.

Quantification of the maximum velocity through the valve, the area of the opening of the valve, calcification, morphology (tricuspid, bicuspid, unicuspid), and size of the valve (annulus, sinuses, sinotubular junction) are common parameters when evaluating the aortic valve.

Invasive measurement of the aortic valve can be done during a cardiac catheterization in which the pressure in the left ventricle and aorta can be measured simultaneously.

Additional images

Related Research Articles

<span class="mw-page-title-main">Coronary circulation</span> Circulation of blood in the blood vessels of the heart muscle (myocardium)

Coronary circulation is the circulation of blood in the arteries and veins that supply the heart muscle (myocardium). Coronary arteries supply oxygenated blood to the heart muscle. Cardiac veins then drain away the blood after it has been deoxygenated. Because the rest of the body, and most especially the brain, needs a steady supply of oxygenated blood that is free of all but the slightest interruptions, the heart is required to function continuously. Therefore its circulation is of major importance not only to its own tissues but to the entire body and even the level of consciousness of the brain from moment to moment. Interruptions of coronary circulation quickly cause heart attacks, in which the heart muscle is damaged by oxygen starvation. Such interruptions are usually caused by coronary ischemia linked to coronary artery disease, and sometimes to embolism from other causes like obstruction in blood flow through vessels.

<span class="mw-page-title-main">Aortic stenosis</span> Narrowing of the exit of the hearts left ventricle

Aortic stenosis is the narrowing of the exit of the left ventricle of the heart, such that problems result. It may occur at the aortic valve as well as above and below this level. It typically gets worse over time. Symptoms often come on gradually with a decreased ability to exercise often occurring first. If heart failure, loss of consciousness, or heart related chest pain occur due to AS the outcomes are worse. Loss of consciousness typically occurs with standing or exercising. Signs of heart failure include shortness of breath especially when lying down, at night, or with exercise, and swelling of the legs. Thickening of the valve without causing obstruction is known as aortic sclerosis.

<span class="mw-page-title-main">Heart valve</span> A flap of tissue that prevent backflow of blood around the heart

A heart valve is a biological one-way valve that allows blood to flow in one direction through the chambers of the heart. Four valves are usually present in a mammalian heart and together they determine the pathway of blood flow through the heart. A heart valve opens or closes according to differential blood pressure on each side.

<span class="mw-page-title-main">Heart sounds</span> Noise generated by the beating heart

Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. Specifically, the sounds reflect the turbulence created when the heart valves snap shut. In cardiac auscultation, an examiner may use a stethoscope to listen for these unique and distinct sounds that provide important auditory data regarding the condition of the heart.

<span class="mw-page-title-main">Mitral valve</span> Valve in the heart connecting the left atrium and left ventricle

The mitral valve, also known as the bicuspid valve or left atrioventricular valve, is one of the four heart valves. It has two cusps or flaps and lies between the left atrium and the left ventricle of the heart. The heart valves are all one-way valves allowing blood flow in just one direction. The mitral valve and the tricuspid valve are known as the atrioventricular valves because they lie between the atria and the ventricles.

<span class="mw-page-title-main">Afterload</span> Pressure in the wall of the left ventricle during ejection

Afterload is the pressure that the heart must work against to eject blood during systole. Afterload is proportional to the average arterial pressure. As aortic and pulmonary pressures increase, the afterload increases on the left and right ventricles respectively. Afterload changes to adapt to the continually changing demands on an animal's cardiovascular system. Afterload is proportional to mean systolic blood pressure and is measured in millimeters of mercury.

<span class="mw-page-title-main">Aortic regurgitation</span> Medical condition

Aortic regurgitation (AR), also known as aortic insufficiency (AI), is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle. As a consequence, the cardiac muscle is forced to work harder than normal.

<span class="mw-page-title-main">Bicuspid aortic valve</span> Medical condition

Bicuspid aortic valve (BAV) is a form of heart disease in which two of the leaflets of the aortic valve fuse during development in the womb resulting in a two-leaflet (bicuspid) valve instead of the normal three-leaflet (tricuspid) valve. BAV is the most common cause of heart disease present at birth and affects approximately 1.3% of adults. Normally, the mitral valve is the only bicuspid valve and this is situated between the heart's left atrium and left ventricle. Heart valves play a crucial role in ensuring the unidirectional flow of blood from the atrium to the ventricles, or from the ventricle to the aorta or pulmonary trunk. BAV is normally inherited.

<span class="mw-page-title-main">Mitral regurgitation</span> Form of valvular heart disease

Mitral regurgitation (MR), also known as mitral insufficiency or mitral incompetence, is a form of valvular heart disease in which the mitral valve is insufficient and does not close properly when the heart pumps out blood. It is the abnormal leaking of blood backwards – regurgitation from the left ventricle, through the mitral valve, into the left atrium, when the left ventricle contracts. Mitral regurgitation is the most common form of valvular heart disease.

Aortic valve replacement is a procedure whereby the failing aortic valve of a patient's heart is replaced with an artificial heart valve. The aortic valve may need to be replaced because:

<span class="mw-page-title-main">Chordae tendineae</span> Inelastic cords of fibrous connective tissue connecting papillary muscles to heart valves

The chordae tendineae or tendinous cords, colloquially known as the heart strings, are inelastic cords of fibrous connective tissue that connect the papillary muscles to the tricuspid valve and the mitral valve in the heart.

A transthoracic echocardiogram (TTE) is the most common type of echocardiogram, which is a still or moving image of the internal parts of the heart using ultrasound. In this case, the probe is placed on the chest or abdomen of the subject to get various views of the heart. It is used as a non-invasive assessment of the overall health of the heart, including a patient's heart valves and degree of heart muscle contraction. The images are displayed on a monitor for real-time viewing and then recorded.

<span class="mw-page-title-main">Artificial heart valve</span> Replacement of a valve in the human heart

An artificial heart valve is a one-way valve implanted into a person's heart to replace a heart valve that is not functioning properly. Artificial heart valves can be separated into three broad classes: mechanical heart valves, bioprosthetic tissue valves and engineered tissue valves.

<span class="mw-page-title-main">Valvular heart disease</span> Disease in the valves of the heart

Valvular heart disease is any cardiovascular disease process involving one or more of the four valves of the heart. These conditions occur largely as a consequence of aging, but may also be the result of congenital (inborn) abnormalities or specific disease or physiologic processes including rheumatic heart disease and pregnancy.

<span class="mw-page-title-main">Aortic valve repair</span> Treatment of aortic regurgitation

Aortic valve repair or aortic valve reconstruction is the reconstruction of both form and function of a dysfunctional aortic valve. Most frequently it is used for the treatment of aortic regurgitation. It can also become necessary for the treatment of aortic aneurysm, less frequently for congenital aortic stenosis.

<span class="mw-page-title-main">Arterial switch operation</span> Open heart surgical procedure

Arterial switch operation (ASO) or arterial switch, is an open heart surgical procedure used to correct dextro-transposition of the great arteries (d-TGA).

<span class="mw-page-title-main">Ascending aorta</span> Part of the heart

The ascending aorta (AAo) is a portion of the aorta commencing at the upper part of the base of the left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the sternum.

The following outline is provided as an overview of and topical guide to cardiology, the branch of medicine dealing with disorders of the human heart. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians who specialize in cardiology are called cardiologists.

References

  1. 1 2 Bayne, Edward J (8 January 2016). "Bicuspid Aortic Valve: Background, Pathophysiology, Epidemiology". Medscape . Retrieved 2 April 2018.
  2. 1 2 3 Ho, SY (January 2009). "Structure and anatomy of the aortic root". European Journal of Echocardiography. 10 (1): i3-10. doi: 10.1093/ejechocard/jen243 . PMID   19131496.
  3. ↑ Anatomy photo:20:29-0104 at the SUNY Downstate Medical Center – "Heart: The Aortic Valve and Aortic Sinuses"
  4. ↑ Last's anatomy, regional and applied (9th. ed.). Churchill Livingstone. 1994. p.  268. ISBN   044304662X.
  5. ↑ "Anatomy of the Heart: Valves". 2019. Retrieved 2019-03-24.
  6. ↑ Crawford, Phillip T.; Arbor, Tafline C.; Bordoni, Bruno (2023). "Anatomy, Thorax, Aortic Valve". StatPearls. StatPearls Publishing. PMID   32662953 . Retrieved 13 December 2023.
  7. ↑ Aortic Valve, Bicuspid at eMedicine
  8. ↑ Hans-Joachim Schäfers: Current treatment of aortic regurgitation. UNI-MED Science, Bremen, London, Boston 2013, ISBN   978-3-8374-1406-6.
  9. ↑ "What is TAVR?". American Heart Association. 2014. Retrieved 2015-08-15.
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