Bicuspid aortic valve

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Bicuspid aortic valve
Other namesBicommissural aortic valve [1]
Bicuspid Aortic Valve.svg
The aortic valve controls outflow of blood from the left ventricle of the heart through the aorta (valve is indicated within the yellow highlighted box). A normal aortic valve is tricuspid. Five types of bicuspid valve are shown, with Type 1 being most prevalent. A bicuspid valve forms when the tissue surrounding one of the cusps (leaflets) of the valve fuses during fetal development. This developmental anomaly can have either a negative or no effect on the individual.
Specialty Cardiology

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. [2] 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.

Contents

Signs and symptoms

In many cases, a bicuspid aortic valve will cause no problems. [3] People with BAV may become tired more easily than those with normal valvular function and have difficulty maintaining stamina for cardio-intensive activities due to poor heart performance caused by stress on the aortic wall. [4] [5] [ citation needed ]

Complications

Calcification

BAV may become calcified later in life, which may lead to varying degrees of severity of aortic stenosis that will manifest as murmurs. [6] If the leaflets do not close correctly, aortic regurgitation can occur. [6] If these become severe enough, they may require heart surgery. The heart is put under more stress in order to either pump more blood through a stenotic valve or attempt to circulate regurgitation blood through a leaking valve. [ clarification needed ] Ultimately there is a risk of rupture in the aortic valve due to bicuspid aortopathy which is a result of progressive aortic dilation from the stress of having only two valve leaflets where three are normal. [4] [7] [5]

Aortic lesions

One of the most notable associations with BAV is the tendency for these patients to present with ascending aortic aneurysmal lesions. [8] The extracellular matrix of the aorta in patients with BAV shows marked deviations from that of the normal tricuspid aortic valve, specifically reduced Fibrillin-1. It is currently believed that an increase in the ratio of MMP2 (Matrix Metalloproteinases 2) to TIMP1 (tissue inhibitors of metalloproteinase) may be responsible for the abnormal degradation of the valve matrix and therefore lead to aortic dissection and aneurysm. [9] However, other studies have also shown MMP9 involvement with no differences in TIMP expression. The size of the proximal aorta should be evaluated carefully during the workup. The initial diameter of the aorta should be noted and annual evaluation with CT scan, or MRI to avoid ionizing radiation, should be recommended to the patient; the examination should be conducted more frequently if a change in aortic diameter is seen. From this monitoring, the type of surgery that should be offered to the patient can be determined based on the change in size of the aorta.[ citation needed ]

Aortic narrowing

A bicuspid aortic valve may cause the heart's aortic valve to narrow (aortic stenosis). [6] This narrowing prevents the valve from opening fully, which reduces or blocks blood flow from the heart to the body. In some cases, the aortic valve does not close tightly, causing blood to leak backward into the left ventricle. [10]

Coarctation of the aorta (a congenital narrowing in the region of the ductus arteriosus) has also been associated with BAV. [11]

Pathophysiology

Heart bicuspid aortic valve anatomy. Heart bicuspid aortic valve.svg
Heart bicuspid aortic valve anatomy.

Fusion of aortic valve leaflets occurs most commonly (≈80%) between the right coronary and left coronary leaflets (RL), which are the anterior leaflets of the aortic valve. [12] [13] Fusion also occurs between the right coronary and noncoronary leaflets (RN, ≈17%), and least commonly between the noncoronary and left coronary leaflets (≈2%). [12] [13] In comparison to other fusion patterns, RN leaflet fusion has a stronger association with future complications such as aortic valve regurgitation and stenosis. [14] [15] However, all fusion patterns associate with a specific area or areas of dilated enlargement in either the root of the ascending aorta, the ascending aorta, or the transverse aortic arch. [12] [13] [14] [16]

Hemodynamics

Identifying hemodynamic patterns in the aorta after left ventricle systole aids in predicting consequential complications of bicuspid aortic valve. [12] [13] [14] The patient-specific risk of developing complications such as aortic aneurysms is dependent on the particular aortic leaflet fusion pattern, with each pattern varying in 4D MRI measurements of wall shear stress (WSS), blood flow velocity, asymmetrical flow displacement and flow angle of the aorta. [12] [13] [16]

BAV outflow is helical and occurs at high velocities (>1 m/s) throughout the ascending aorta. [12] [13] [14] This is potentially more damaging to the aorta in comparison to the streamline flow and short-lived burst of high velocity at the beginning of the aorta, as seen within a healthy tricuspid valve. [12] This eccentric outflow from the BAV results in blood hitting and reflecting off the aortic wall in a non-streamline fashion. [12] [13] The specific zones where blood hits is dependent on the varying BAV leaflet fusion patterns and consequently correlates with increases in WSS. [12] [16] WSS measurements in RL fusion indicate an increase in pressure applied predominantly to the right-anterior side of the vessel wall, while RN fusion increases WSS on the right-posterior wall. [12] [16] The resulting rise in WSS is supported by the asymmetrical displacement of blood flow produced by an increased angle of outflow from the BAV. [12] [13] Displacement is measured as the distance in millimeters from the center of the aorta to the center of the high velocity outflow. [12] Blood does not flow centrally through the aorta in BAV, but along the right-anterior and right-posterior vessel wall for RL and RN leaflet fusion respectively. [12] [13]

Aortic disease

Identification of hemodynamics for RL, RN, and left coronary and noncoronary leaflet fusion patterns enables detection of specific aortic regions susceptible to dysfunction and the eventual development of disease. [12] [13] Specifically, RL and RN fusion patterns are more likely to develop into these aortic disease states. [12] [13] The blood flow information associated with RL fusion causes dilation of the mid-ascending aorta, while RN fusion is associated with dilation in the root, distal ascending aorta and transverse arch. [12] [14] BAV helical and high velocity outflow patterns are consistent with aortic dilation hemodynamics seen in those with tricuspid aortic valves. [17] However, it is the increase and variance in WSS and flow displacement in BAV that demonstrate the importance of aortic leaflet morphology. [12] Flow displacement measurements taken from 4D MRI may be best for detecting irregularities in hemodynamics. [12] Displacement measurements were highly sensitive and distinguishable between different valve morphologies. [12] Hemodynamic measurements from 4D MRI in patients with BAV are advantageous in determining the timing and location of repair surgery to the aorta in aortopathy states. [12]

Most patients with bicuspid aortic valve whose valve becomes dysfunctional will need careful follow-up and potentially valve replacement at some point in life. Regular EchoCG and MRI may be performed.[ citation needed ]If the valve is normally functioning or minimally dysfunctional, average lifespan is similar to that of those without the anomaly. [18]

Diagnosis

Heart bicuspid aortic valve diagram Heart bicuspid aortic lpla.svg
Heart bicuspid aortic valve diagram

A bicuspid aortic valve can be associated with a heart murmur located at the right second intercostal space. Often there will be differences in blood pressures between upper and lower extremities. The diagnosis can be assisted with echocardiography or magnetic resonance imaging (MRI). Four-dimensional magnetic resonance imaging (4D MRI) is a technique that defines blood flow characteristics and patterns throughout the vessels, across valves, and in compartments of the heart. [12] [13] [19] Four-dimensional imaging enables accurate visualizations of blood flow patterns in a three-dimensional (3D) spatial volume, as well as in a fourth temporal dimension. [12] [14] [17] [19] Current 4D MRI systems produces high-resolution images of blood flow in just a single scan session. [12] [19]

Classification

Bicuspid aortic valves may assume three different types of configuration: [20]

  1. "Real" bicuspid valves with two symmetric leaflets
  2. A tricuspid architecture with a fusion of two leaflets
  3. A tricuspid architecture with a fusion of three leaflets

Treatment

Complications stemming from structural heart issues are most often treated through surgical intervention, which could include aortic valve replacement, or balloon valvuloplasty. [21]

Prognosis

BAV frequently leads to significant complications in over one-third of affected individuals which often lead to significant morbidity and mortality. [22] Notable complications of BAV include narrowing of the aortic valve opening, backward blood flow at the aortic valve, dilation of the ascending aorta, and infection of the heart valve. [22]

If aortic regurgitation and dilation of the ascending aorta are noted in someone, they should undergo yearly surveillance with transthoracic echocardiograms if the aortic root measures 4.5 centimeters or greater in diameter.[ citation needed ]

Epidemiology

Bicuspid aortic valves are the most common cardiac valvular anomaly, occurring in 1–2% of the general population. It is twice as common in males as in females. [23]

Bicuspid aortic valve is a heritable condition, with a demonstrated association with mutations in the NOTCH1 gene. [24] Its heritability () is as high as 89%. [25] Both familial clustering and isolated valve defects have been documented. Recent studies suggest that BAV is an autosomal dominant condition with incomplete penetrance. Other congenital heart defects are associated with bicuspid aortic valve at various frequencies, including coarctation of the aorta. [26]

Bicuspid aortic valve abnormality is also the most observed cardiac defect in Turner syndrome. [27]

Related Research Articles

<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 narrowing 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">Aortic valve</span> Valve in the human heart between the left ventricle and the aorta

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. The aortic valve is the last structure in the heart the blood travels through before stopping the flow through the systemic circulation.

<span class="mw-page-title-main">Aortic dissection</span> Injury to the innermost layer of the aorta

Aortic dissection (AD) occurs when an injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart. In most cases, this is associated with a sudden onset of severe chest or back pain, often described as "tearing" in character. Vomiting, sweating, and lightheadedness may also occur. Damage to other organs may result from the decreased blood supply, such as stroke, lower extremity ischemia, or mesenteric ischemia. Aortic dissection can quickly lead to death from insufficient blood flow to the heart or complete rupture of the aorta.

<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">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.

<span class="mw-page-title-main">Coarctation of the aorta</span> Medical condition

Coarctation of the aorta, also called aortic narrowing, is a congenital condition whereby the aorta is narrow, usually in the area where the ductus arteriosus inserts. The word coarctation means "pressing or drawing together; narrowing". Coarctations are most common in the aortic arch. The arch may be small in babies with coarctations. Other heart defects may also occur when coarctation is present, typically occurring on the left side of the heart. When a patient has a coarctation, the left ventricle has to work harder. Since the aorta is narrowed, the left ventricle must generate a much higher pressure than normal in order to force enough blood through the aorta to deliver blood to the lower part of the body. If the narrowing is severe enough, the left ventricle may not be strong enough to push blood through the coarctation, thus resulting in a lack of blood to the lower half of the body. Physiologically its complete form is manifested as interrupted aortic arch.

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:

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">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">Aortic valvuloplasty</span>

Aortic valvuloplasty, also known as balloon aortic valvuloplasty (BAV), is a procedure used to improve blood flow through the aortic valve in conditions that cause aortic stenosis, or narrowing of the aortic valve. It can be performed in various patient populations including fetuses, newborns, children, adults, and pregnant women. The procedure involves using a balloon catheter to dilate the narrowed aortic valve by inflating the balloon.

Regurgitation is blood flow in the opposite direction from normal, as the backward flowing of blood into the heart or between heart chambers. It is the circulatory equivalent of backflow in engineered systems. It is sometimes called reflux.

<span class="mw-page-title-main">Ross procedure</span> Type of cardiac surgical operation

The Ross procedure, also known as pulmonary autograft, is a heart valve replacement operation to treat severe aortic valve disease, such as in children and young adults with a bicuspid aortic valve. It involves removing the diseased aortic valve, situated at the exit of the left side of the heart, and replacing it with the person's own healthy pulmonary valve (autograft), removed from the exit of the heart's right side. To reconstruct the right sided exit, a pulmonary valve from a cadaver (homograft), or a stentless xenograft, is used to replace the removed pulmonary valve. Compared to a mechanical valve replacement, it avoids the requirement for thinning the blood, has favourable blood flow dynamics, allows growth of the valve with growth of the child and has less risk of endocarditis.

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.

<span class="mw-page-title-main">Ventricular outflow tract obstruction</span> Medical condition

A ventricular outflow tract obstruction is a heart condition in which either the right or left ventricular outflow tract is blocked or obstructed. These obstructions represent a spectrum of disorders. Majority of these cases are congenital, but some are acquired throughout life.

<span class="mw-page-title-main">Hybrid cardiac surgery</span>

A hybrid cardiac surgical procedure in a narrow sense is defined as a procedure that combines a conventional, more invasive surgical part with an interventional part, using some sort of catheter-based procedure guided by fluoroscopy imaging in a hybrid operating room (OR) without interruption. The hybrid technique has a reduced risk of surgical complications and has shown decreased recovery time. It can be used to treat numerous heart diseases and conditions and with the increasing complexity of each case, the hybrid surgical technique is becoming more common.

<span class="mw-page-title-main">Apicoaortic conduit</span> Cardiothoracic surgical process

Apicoaortic Conduit (AAC), also known as Aortic Valve Bypass (AVB), is a cardiothoracic surgical procedure that alleviates symptoms caused by blood flow obstruction from the left ventricle of the heart. Left ventricular outflow tract obstruction (LVOTO) is caused by narrowing of the aortic valve (aortic stenosis) and other valve disorders. AAC, or AVB, relieves the obstruction to blood flow by adding a bioprosthetic valve to the circulatory system to decrease the load on the aortic valve. When an apicoaortic conduit is implanted, blood continues to flow from the heart through the aortic valve. In addition, blood flow bypasses the native valve and exits the heart through the implanted valved conduit. The procedure is effective at relieving excessive pressure gradient across the natural valve. High pressure gradient across the aortic valve can be congenital or acquired. A reduction in pressure gradient results in relief of symptoms.

<span class="mw-page-title-main">Hemodynamics of the aorta</span> Study of the flow patterns and forces in the thoracic aorta

The hemodynamics of the aorta is an ongoing field of research in which the goal is to identify what flow patterns and subsequent forces occur within the thoracic aorta. These patterns and forces are used to identify the presence and severity of cardiovascular diseases such as aortic aneurysm and atherosclerosis. Some of the methods used to study the hemodynamics of aortic flow are patient scans, computational fluid dynamics models, and particle tracking velocimetry (PTV). The information gathered through these studies can be used for surgery planning and the development of implants. Greater understanding of this topic reduces mortality rates associated with cardiovascular disease.

References

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  2. ↑ Verma, S; Siu, SC (May 2014). "Aortic dilatation in patients with bicuspid aortic valve". New England Journal of Medicine (Review). 370 (20): 1920–9. doi:10.1056/NEJMra1207059. PMID   24827036. S2CID   55778596.
  3. ↑ "Atrial Septal Defect". Commonly Asked Questions About Children and Heart Disease. October 29, 2012. Retrieved April 9, 2014.
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  8. ↑ Davies, Ryan R.; Kaple, Ryan K.; Mandapati, Divakar; Gallo, Amy; Botta, Donald M.; Elefteriades, John A.; Coady, Michael A. (April 2007). "Natural History of Ascending Aortic Aneurysms in the Setting of an Unreplaced Bicuspid Aortic Valve". The Annals of Thoracic Surgery. 83 (4): 1338–1344. doi:10.1016/j.athoracsur.2006.10.074.
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  10. ↑ Aortic valve stenosis (AVS). American Heart Association. http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/AboutCongenitalHeartDefects/Aortic-Valve-Stenosis-AVS_UCM_307020_Article.jsp#.WclzKdjrvcs. Accessed December 23, 2018.
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  13. 1 2 3 4 5 6 7 8 9 10 11 12 Bissell MM, Hess AT, Biasiolli L, et al. (July 2013). "Aortic dilation in bicuspid aortic valve disease: flow pattern is a major contributor and differs with valve fusion type". Circulation: Cardiovascular Imaging. 6 (4): 499–507. doi:10.1161/CIRCIMAGING.113.000528. PMC   3859916 . PMID   23771987.
  14. 1 2 3 4 5 6 Hope MD, Hope TA, Meadows AK, et al. (April 2010). "Bicuspid aortic valve: four-dimensional MR evaluation of ascending aortic systolic flow patterns". Radiology. 255 (1): 53–61. doi:10.1148/radiol.09091437. PMID   20308444.
  15. ↑ Fernandes SM, Sanders SP, Khairy P, et al. (October 2004). "Morphology of bicuspid aortic valve in children and adolescents". Journal of the American College of Cardiology. 44 (8): 1648–51. doi: 10.1016/j.jacc.2004.05.063 . PMID   15489098.
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  17. 1 2 Weigang E, Kari FA, Beyersdorf F, et al. (July 2008). "Flow-sensitive four-dimensional magnetic resonance imaging: flow patterns in ascending aortic aneurysms". European Journal of Cardio-Thoracic Surgery. 34 (1): 11–6. doi: 10.1016/j.ejcts.2008.03.047 . PMID   18515137.
  18. ↑ Michelena HI, Desjardins VA, Avierinos JF, et al. (May 2008). "Natural history of asymptomatic patients with normally functioning or minimally dysfunctional bicuspid aortic valve in the community". Circulation. 117 (21): 2776–84. doi:10.1161/CIRCULATIONAHA.107.740878. PMC   2878133 . PMID   18506017.
  19. 1 2 3 Markl M, Chan FP, Alley MT, et al. (April 2003). "Time-resolved three-dimensional phase-contrast MRI". Journal of Magnetic Resonance Imaging. 17 (4): 499–506. doi:10.1002/jmri.10272. PMID   12655592.
  20. ↑ Kumme, Anja (2007). Klassifikation bikuspider Aortenklappen. OCLC   254078723.[ page needed ]
  21. ↑ Mohler ER, et al. Management of thoracic aortic aneurysm in adults. https://www.uptodate.com/contents/search. Accessed December 23rd, 2018.
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  24. ↑ Garg V, Muth AN, Ransom JF, et al. (2005). "Mutations in NOTCH1 cause aortic valve disease". Nature. 437 (7056): 270–274. Bibcode:2005Natur.437..270G. doi:10.1038/nature03940. PMID   16025100.
  25. ↑ Cripe L, Andelfinger G, Martin LJ, Shooner K, Benson DW (July 2004). "Bicuspid aortic valve is heritable". Journal of the American College of Cardiology. 44 (1): 138–43. doi: 10.1016/j.jacc.2004.03.050 . PMID   15234422.
  26. ↑ Blackbourne, Lorne H.; Chhabra, Anikar, eds. (2002). "Congenital Heart Disease". Pathology Recall. Lippincott Williams & Wilkins. pp. 247–9. ISBN   978-0-7817-3406-6.
  27. ↑ Bondy, Carolyn; Bakalov, Vladimir K.; Cheng, Clara; Olivieri, Laura; Rosing, Douglas R.; Arai, Andrew E. (1 October 2013). "Bicuspid aortic valve and aortic coarctation are linked to deletion of the X chromosome short arm in Turner syndrome". Journal of Medical Genetics. 50 (10): 662–665. doi: 10.1136/jmedgenet-2013-101720 . ISSN   0022-2593. PMC   3786649 . Retrieved 13 December 2022.
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