Mitral valve replacement

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Mitral valve replacement
ICD-9-CM 35.23-35.24

Mitral valve replacement is a procedure whereby the diseased mitral valve of a patient's heart is replaced by either a mechanical or tissue (bioprosthetic) valve.

Contents

The mitral valve may need to be replaced because:[ citation needed ]

Causes of mitral valve disease include infection, calcification and inherited collagen disease. Current mitral valve replacement approaches include open heart surgery and minimally invasive cardiac surgery (MICS).

Normal mitral valve anatomy and physiology

From left to right: Fluid jetting from the left atrium through the mitral valve into the left ventricle, fluid creating a vortex near the apex in the left ventricle, and fluid being redirected out of the left ventricle through the aortic valve. VORTEX FORMATION IN THE LEFT HEART.png
From left to right: Fluid jetting from the left atrium through the mitral valve into the left ventricle, fluid creating a vortex near the apex in the left ventricle, and fluid being redirected out of the left ventricle through the aortic valve.

The mitral valve is a bileaflet valve sited between the left atrium and left ventricle, responsible for preventing blood flowing from the ventricle to the atrium when the heart contracts. It is elliptical, and its area varies from 5.0 to 11.4 cm2. The valve leaflets are separated by two commissures, and each leaflet of the valve (anterior leaflet, the large one, and posterior leaflet, the small one) has three sections (p1, p2, p3). Histologically, each leaflet is composed of the solid fibrosa, the spongiosa at the atrial surface and another fibroelastic layer covering the leaflets. [1] Two papillary muscles originating from the base of the left ventricle hold the mitral leaflets in place through chordae tendinae, which insert the edge of the leaflets, preventing them from leaking during left ventricle systole. [2]

Vortex Formation

During normal mitral valve function fluid jets from the left atrium through the mitral valve into the left ventricle. The vortex created from this jetting travels towards the apex of the left ventricle because of the asymmetric shape of the mitral valve leaflets. This vortex rotates clockwise until the isovolumetric contraction of the left ventricle opens the aortic valve and redirects the fluid flow from the apex of the left ventricle to the systemic circulation and the rest of the body.[ citation needed ]

The asymmetry of the mitral valve is very important in the diastolic flow patterns of transmitral flow. Additionally the entire systems; the mitral annulus, papillary muscles and the chordae tendinea all play a vital role in forming a sophisticated vortex that optimizes the fluid flow in the left heart. Simulations have been performed showing how all of these aspects of the mitral valve contribute to the normal vortex formation in the left heart. [3] [4]

Mitral stenosis and regurgitation

The most common cause of mitral stenosis is rheumatic fever, seen mostly in the developing world. Other causes are mitral degenerative disease, severe calcification (elderly), congenital deformities, malignant carcinoid syndrome, neoplasm, left atrial appendage thrombus, endocarditic vegetations, certain inherited metabolic diseases, or complications of previous procedures at the aortic valve. [5] Mitral stenosis causes left atrial pressure to increase, which, if left untreated, can lead to ventricular dilation, hypertrophy, atrial fibrillation, and thrombus creation. Symptoms include shortness of breath (dyspnea) on exertion, when lying flat (orthopnea) or during the night (paroxysmal nocturnal dyspnea), and fatigue. [6]

If mitral leaflets don't coapt (close) effectively, blood flows backwards (regurgitation) from the left ventricle towards the left atrium during systole. The most common causes are myxomatous degeneration (Barlow disease), ischemic heart disease, dilated cardiomyopathy, rheumatic valve disease, mitral annular calcification, infective endocarditis, congenital anomalies, endocardial fibrosis, myocarditis, and collagen-vascular disorders. [7] The most used system to classify mitral valve regurgitation is Carpentier's classification, which separates mitral regurgitation into three types, depending on the leaflet motion in relation to the mitral annular plane:[ citation needed ]

Artificial valve types

There are two main types of artificial mitral valve: mechanical valves and tissue (bioprosthetic) valves. [8] They come in various sizes (commonly starting from an external diameter of 19 mm and increasing by 2 mm per model). [9]

Mechanical valves

Mechanical valves are made from metal and/or pyrolitic carbon, [10] and can last 20–30 years. [11] The risk of blood clots forming is higher with mechanical valves than with bioprosthetic valves. As a result, patients with mechanical valves must take blood-thinning medication (anticoagulants) for the rest of their lives, making them more prone to bleeding. [11]

There are three types of mechanical valves:

  1. Caged ball valve (not in use any more)
  2. Tilting disc
  3. Bileaflet disc

Bileaflet valves are the most common type of mechanical valve, offering desirable haemodynamics. [12] The two leaflets of a bileaflet disc valve open during diastole and close during systole.[ citation needed ]

Bioprosthetic valves

Bioprosthetic valves are made from animal tissues. Most people with bioprosthetic valves don’t need to take anticoagulants long term. However, bioprosthetic valves may only last 10–15 years. [11] They tend to deteriorate more quickly in younger patients. [11] Valve failure prevalence at 10 years is 30%, increasing to 35–65% at 15 years. [13] New tissue preservation technologies are being studied to try to increase the durability of bioprosthetic valves. [14]

Valve selection

The choice of valve depends upon the patient's age, medical condition, preferences, and lifestyle. [11] Typically, patients younger than 65 years old will receive a mechanical valve unless they are unable to take long-term anticoagulation, and patients older than 70 years will receive a bioprosthetic valve. [8]

Procedure

The most common approach for surgeons to reach the heart is a median sternotomy (vertically cutting the breastbone), but other incisions can be employed, such as a left or right thoracotomy. [15] After the heart is exposed, the patient is put on a cardiopulmonary bypass machine, also known as a heart–lung machine. This machine breathes for the patient and pumps their blood around their body – bypassing the heart – while the surgeon replaces the heart valve. Next, an aortic clamp is placed on the aorta, and the heart is stopped (cardioplegia). [15] Depending on the pathology of the mitral valve and surgeon's preference, various approaches can be used to access the mitral valve. The interatrial groove approach involves incising the left atrium posterior to the interatrial groove. The transatrial oblique approach is utilized when the left atrium is small. In this approach, the right atrium is opened and another incision is made at the interatrial septum. [16]

The valve is excised 4–5 mm from the annulus, leaving intact the attached chordae unless they are calcified or otherwise diseased. The valve is replaced by a mechanical or bioprosthetic valve. The replacement valve is sewn into the annulus with interrupted or horizontal mattress sutures with the pledgets on the atrial side. [17] The atrial walls are closed, taking care not to trap air within the chambers of the heart. [18] The heart is restarted, and the patient is taken off the heart–lung machine.[ citation needed ]

Recovery

Following surgery, patients are typically taken to an intensive care unit for monitoring. They may need a respirator to help them breathe for the first few hours or days after surgery. The patient should be able to sit up in bed within 24 hours. After two days, the patient may be moved out of the intensive care unit. Patients are usually discharged after 7–10 days. If the mitral valve replacement is successful, patients can expect their symptoms to improve significantly. [19]

Some scarring occurs after surgery. After median sternotomy, the patient will have a vertical scar on their chest above their breastbone. If the heart is accessed from under the left breast there will be a smaller scar in this location. [20]

Patients with a bioprosthetic mitral valve are prescribed anticoagulants, such as warfarin, for 6 weeks to 3 months after their operation, while patients with mechanical valves are prescribed anticoagulants for the rest of their lives. Anticoagulants are taken to prevent blood clots, which can move to other parts of the body and cause serious medical problems, such as a heart attack. Anticoagulants will not dissolve a blood clot but they do prevent other clots from forming or prevent clots from becoming larger. [21]

Once their wounds have healed, patients should have few, if any, restrictions from daily activities. People are advised to walk or undertake other physical activities gradually to regain strength. Patients who have physically demanding jobs will have to wait a little longer than those who don’t. Patients are also restricted from driving a car for six weeks after the surgery.[ citation needed ]

Complications

As with other cardiac procedures, mitral valve replacement is associated with risks, such as bleeding, infection, thromboembolism, renal shutdown, cardiac tamponade, stroke, or reaction to anesthesia. [22] The risk of death is about 1%. [23] Risks depend on a patient’s age, general health, specific medical conditions, and heart function. [24]

Flipped Vortex Circulation

Pedrizetti et al. [25] studied the fluid mechanics in the left heart in 40 randomized patients with mechanical and tissue artificial heart valves. Using echocardiography they quantitatively analyzed the velocity field in the left heart and found that the patients with artificial mitral valves had a consistent counterclockwise circulation, as opposed to the normal clockwise circulation that is characteristic of normal transmitral flow.[ citation needed ]

To further characterize this counterclockwise circulation a numerical simulation was performed which backed up the data taken from the echocardiograph study.[ citation needed ]

This flipped vortex circulation could lead to further complications in the patient who had mitral valve replacement surgery as it was observed to cause stagnation points, crossed flows, increased energy requirements and pressure shifts from the lateral to the septal wall in the left heart.[ citation needed ]

Minimally invasive mitral valve replacement

Since the 1990s, surgeons have been working on less invasive approaches to mitral valve surgery, known as minimally invasive cardiac surgery (MICS). Minimally invasive mitral valve replacement involves a small incision (5–8 cm) just below the right breast. The benefits of MICS over conventional surgery include reduced hospital stay and blood transfusion requirements, and a smaller scar. [26]

Transcatheter mitral valve replacement

Rather than removing the existing valve, transcatheter mitral valve replacement [27] involves wedging a new valve into the site of the existing valve. The replacement valve is delivered to the site of the existing valve through a tube called a catheter. The catheter may be inserted through the femoral artery in the thigh, or through a small incision in the chest. [28] Once the replacement valve is in place, it is expanded, pushing the old valve’s leaflets (the sections that open and close) out of the way. [29] [30] [31]

Alternatives to mitral valve replacement

Repair

Many mitral valves can be repaired instead of replaced. In fact, mitral valve repair is recommended by international guidelines wherever possible. [32] [33] Advantages of mitral valve repair over replacement include lower surgical mortality (~1% for repair vs ~5% for replacement [34] ), lower rates of stroke and endocarditis (an infection of the heart’s inner lining), equivalent or better long‑term durability, [35] [36] [37] and improved long-term survival. [35] Patients who have their valve repaired have a similar life expectancy to the general population. [38] In addition, patients may not need to take anticoagulants long term following mitral valve repair. [39]

Non-surgical options

For individuals with few symptoms, or those with contraindications to surgery, options exist for medical treatment in both mitral insufficiency and mitral valve stenosis, although they won't cure the conditions. Such medical treatments include diuretics, [40] [41] vasodilators, [41] [40] and ACE inhibitors. [40] [42] [43]

See also

Related Research Articles

<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">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">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">Tricuspid valve</span> One-way valve present between right auricle and right ventricle

The tricuspid valve, or right atrioventricular valve, is on the right dorsal side of the mammalian heart, at the superior portion of the right ventricle. The function of the valve is to allow blood to flow from the right atrium to the right ventricle during diastole, and to close to prevent backflow (regurgitation) from the right ventricle into the right atrium during right ventricular contraction (systole).

<span class="mw-page-title-main">Mitral valve prolapse</span> Medical condition

Mitral valve prolapse (MVP) is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. It is the primary form of myxomatous degeneration of the valve. There are various types of MVP, broadly classified as classic and nonclassic. In severe cases of classic MVP, complications include mitral regurgitation, infective endocarditis, congestive heart failure, and, in rare circumstances, cardiac arrest.

<span class="mw-page-title-main">Mitral stenosis</span> Heart disease with narrowing of valve

Mitral stenosis is a valvular heart disease characterized by the narrowing of the opening of the mitral valve of the heart. It is almost always caused by rheumatic valvular heart disease. Normally, the mitral valve is about 5 cm2 during diastole. Any decrease in area below 2 cm2 causes mitral stenosis. Early diagnosis of mitral stenosis in pregnancy is very important as the heart cannot tolerate increased cardiac output demand as in the case of exercise and pregnancy. Atrial fibrillation is a common complication of resulting left atrial enlargement, which can lead to systemic thromboembolic complications such as stroke.

<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">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 cardiac surgery procedure whereby a failing aortic valve is replaced with an artificial heart valve. The aortic valve may need to be replaced because of aortic regurgitation, or if the valve is narrowed by stenosis.

<span class="mw-page-title-main">Atrium (heart)</span> Part of the human heart

The atrium is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves.

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">Atrioventricular septal defect</span> Medical condition

Atrioventricular septal defect (AVSD) or atrioventricular canal defect (AVCD), also known as "common atrioventricular canal" or "endocardial cushion defect" (ECD), is characterized by a deficiency of the atrioventricular septum of the heart that creates connections between all four of its chambers. It is a very specific combination of 3 defects:

<span class="mw-page-title-main">Mitral valve repair</span> Cardiac surgery procedure

Mitral valve repair is a cardiac surgery procedure performed by cardiac surgeons to treat stenosis (narrowing) or regurgitation (leakage) of the mitral valve. The mitral valve is the "inflow valve" for the left side of the heart. Blood flows from the lungs, where it picks up oxygen, through the pulmonary veins, to the left atrium of the heart. After the left atrium fills with blood, the mitral valve allows blood to flow from the left atrium into the heart's main pumping chamber called the left ventricle. It then closes to keep blood from leaking back into the left atrium or lungs when the ventricle contracts (squeezes) to push blood out to the body. It has two flaps, or leaflets, known as cusps.

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">Tricuspid regurgitation</span> Type of valvular heart disease

Tricuspid regurgitation (TR), also called tricuspid insufficiency, is a type of valvular heart disease in which the tricuspid valve of the heart, located between the right atrium and right ventricle, does not close completely when the right ventricle contracts (systole). TR allows the blood to flow backwards from the right ventricle to the right atrium, which increases the volume and pressure of the blood both in the right atrium and the right ventricle, which may increase central venous volume and pressure if the backward flow is sufficiently severe.

<span class="mw-page-title-main">Lutembacher's syndrome</span> Medical condition

Lutembacher's syndrome is a very rare form of congenital heart disease that affects one of the chambers of the heart as well as a valve. It is commonly known as both congenital atrial septal defect (ASD) and acquired mitral stenosis (MS). Congenital atrial septal defect refers to a hole being in the septum or wall that separates the two atria; this condition is usually seen in fetuses and infants. Mitral stenosis refers to mitral valve leaflets sticking to each other making the opening for blood to pass from the atrium to the ventricles very small. With the valve being so small, blood has difficulty passing from the left atrium into the left ventricle. Septal defects that may occur with Lutembacher's syndrome include: Ostium primum atrial septal defect or ostium secundum which is more prevalent.

Mitral valve annuloplasty is a surgical technique for the repair of leaking mitral valves. Due to various factors, the two leaflets normally involved in sealing the mitral valve to retrograde flow may not coapt properly. Surgical repair typically involves the implantation of a device surrounding the mitral valve, called an annuloplasty device, which pulls the leaflets together to facilitate coaptation and aids to re-establish mitral valve function.

<span class="mw-page-title-main">MitraClip</span>

MitraClip is a medical device used to treat mitral valve regurgitation for individuals who should not have open-heart surgery. It is implanted via a tri-axial transcatheter technique and involves suturing together the anterior and posterior mitral valve leaflets.

References

  1. ↑ Fann, Ingels & Miller 2017, p. 761.
  2. ↑ Fann, Ingels & Miller 2017, p. 784.
  3. ↑ Sotiropoulos, Fotis; Le, Trung Bao; Gilmanov, Anvar (2016-01-03). "Fluid Mechanics of Heart Valves and Their Replacements". Annual Review of Fluid Mechanics. 48 (1): 259–283. Bibcode:2016AnRFM..48..259S. doi: 10.1146/annurev-fluid-122414-034314 . ISSN   0066-4189.
  4. ↑ Votta, Emiliano; Le, Trung Bao; Stevanella, Marco; Fusini, Laura; Caiani, Enrico G; Redaelli, Alberto; Sotiropoulos, Fotis (2013). "Toward patient-specific simulations of cardiac valves: State-of-the-art and future directions". Journal of Biomechanics. 46 (2): 217–228. doi:10.1016/j.jbiomech.2012.10.026. ISSN   0021-9290. PMC   3552085 . PMID   23174421.
  5. ↑ Fann, Ingels & Miller 2017, p. 764.
  6. ↑ Fann, Ingels & Miller 2017, p. 767.
  7. 1 2 Fann, Ingels & Miller 2017, p. 770.
  8. 1 2 van der Merwe, J (2017). "Mitral Valve Replacement-Current and Future Perspectives". Open Journal of Cardiovascular Surgery. 9: 1179065217719023. doi:10.1177/1179065217719023. PMC   5513524 . PMID   28757798.
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  37. ↑ Mohty, D.; Orszulak, T.A.; Schaff, H.V. (2001). "Very long-term survival and durability of mitral valve repair for mitral valve prolapse". ACC Current Journal Review. 11 (2): 78. doi:10.1016/s1062-1458(02)00576-7. ISSN   1062-1458.
  38. ↑ Vassileva, Christina M.; Mishkel, Gregory; McNeely, Christian; Boley, Theresa; Markwell, Stephen; Scaife, Steven; Hazelrigg, Stephen (2013-05-07). "Long-Term Survival of Patients Undergoing Mitral Valve Repair and Replacement: A Longitudinal Analysis of Medicare Fee-for-Service Beneficiaries". Circulation. 127 (18): 1870–1876. doi: 10.1161/CIRCULATIONAHA.113.002200 . ISSN   0009-7322. PMID   23569153.
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  40. 1 2 3 VOC=VITIUM ORGANICUM CORDIS, a compendium of the Department of Cardiology at Uppsala Academic Hospital. By Per Kvidal September 1999, with revision by Erik Björklund May 2008
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