AORTIC VALVE: anatomy, functions, pathologies and interventions

What is the aortic valve

What is the aortic valve? There aortic valve, Also called aortic semilunar valve, it is a heart valve that allows blood flow from the heart to the body's circulatory system. The aortic valve is formed by 3 flaps (cusps) and has an average diameter of 20 mm. Understanding the function of the aortic valve requires a brief review of the heart's anatomy.

Anatomy of the heart

The heart is a pumping organ blood across the circulatory system with a frequency of 70 beats for minute; a human heart contracts approximately 100,800 times in a day, more than 36 million times in a year and about 3 billion times over an 80-year life span.

The heart it is made up four heart chambers, two atria and two ventricles, whose function is to send the deoxygenated blood ai lungs and allow the passage of oxygenated blood to the rest of the body and by four valves that have the purpose of giving unidirectionality to the blood and making the heart chambers similar to airtight chambers in order to avoid blood loss or reflux.

The valves of the heart are structures of collagen covered by a continuous layer of endothelium which covers the entire cardiovascular system. The valves located at the outlet of the ventricles are the aortic valve is pulmonary valve that have three cusps, that is, three flaps. These valves are forced to open by ventricular contraction (ventricular systole) and close due to pressure in the aorta and pulmonary artery as the left ventricle and right ventricle release (ventricular diastole). Finally we have the valves placed in communication between the atrium and the ventricle: the tricuspid valve and the mitral valve, which, compared to the two previously mentioned, close in the phase of ventricular contraction and open in the phase of relaxation.

Heart valves

Anatomy of the heart with heart valves and emergence of the large arterial and venous vessels, the aorta and the pulmonary veins.

All these elements are the protagonists of the cardiac cycle consisting of the alternation of ventricular systole and diastole, which correspond respectively to the ejection and filling phase of the ventricles.

The cardiac cycle, reviewed in a very schematic way, it is as follows:

  • deoxygenated blood from peripheral tissues->
  • right atrium->
  • tricuspid valve->
  • right ventricle->
  • pulmonary arteries->
  • lungs->
  • oxygenated blood->
  • pulmonary veins->
  • left atrium->
  • mitral valve->
  • left ventricle->
  • aortic valve->
  • aorta->
  • peripheral tissues

In this article we will deal with the aortic valve.

3D image of the tricuspid aortic valve, with reconstruction of the beginning of the coronaries. Siemens Acuson SC2000

Anatomy of the aortic valve

As for the mitral valve also for the aortic valve we can speak of the valvular apparatus, in this case between the sinotubular junction at the top and the ventricular side of the flaps at the bottom.

The aortic valve consists of a fibrous annulus consisting of three rings of semicircular collagen to which they are attached three semilunar cusps, shaped nest of swallow, from which the aortic sinuses, also called breasts of Valsalva, one for each cusp.

The aortic cusps are divided into:

  • posterior cusp
  • right cusp
  • left cusp

On the free margin of each cusp there are i nodules of Aranzio, that allow a perfect closing of the valve during ventricular diastole and who are the first to undergo a senile degenerative process with consequent aortic insufficiency.

In a normal aortic valve we generally have three aortic sinuses :

  • left aortic sinus, from which the left coronary artery originates;
  • right aortic sinus, from which the right coronary artery departs;
  • posterior aortic sinus, from which they usually do not originate coronary arteries.

Recall that the coronary arteries are the arterial branches that supply the heart and whose closure can lead to heart attack myocardium. When the pressure in the left ventricle increases, it exceeds the aortic pressure and the valve flaps are passively open. During the aetius, most of the blood goes into the ascending aorta, but another part enters the sinuses.

During the diastole approximately 4% of ejected blood regurgitates through a valve with normal sinuses.

There are several pathologies that can affect the aortic valve and the causes are the most diverse: from congenital pathologies already present at birth to physiological senile degenerations, due to age. The most frequent congenital pathology is usually aortic bicuspidia (in fact usually there is a tricuspid aortic valve). As a degenerative pathology we most frequently have aortic stenosis which can more or less be associated with aortic insufficiency

Let's see them one by one.

 

Aortic valve

Image of aortic valve and ascending aorta. This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Congenital valve disorders

Bicuspid aorta

The most common congenital malformation is the bicuspid aorta, one of the cusps is rudimentary, the others appear morphologically normal. Unless it is the site of associated dysplasia, this valve is not stenotic from birth, but becomes stenotic later on.

There aortic stenosis it is usually secondary to fibrosis and calcification of the cusps.

Calcific deposits usually form nodules at the base of the cusps in the sinuses of Valsalva and extend, though often not involving, to the upper portions. In addition, there are foci of calcification and extensive fibrosis within the cusps. The fusion of the commissures is usually minimal and involves only one commissure.

We must also remember the close correlation between aortic bicuspidia and increased susceptibility to infective endocarditis.
As for the bicuspid aortic valve and sport, on the other hand, there are no particular contraindications; if you are aware of bicuspidy it will be sufficient to carry out occasional cardiological checks to verify that there is no insufficiency.

Other cusp changes that are very rare compared to bicuspid are quadricuspid or unicuspid aortic valve. The most frequent indication for surgery on these valves is the onset of severe aortic insufficiency.

Write down Type of Aortic Valve

Published by Sultania Cardiovascular Sciences on Wednesday 28 March 2018

Aortic stenosis

There aortic stenosis it is a narrowing of the aortic valve orifice that may obstruct the flow of blood from the left ventricle to the rest of the body. It is the most common aortic disease in adults in the Western world.

The obstruction of the outflow tract of the left ventricle is usually localized at the level of the valve ring, but sometimes supravalvular and subvalvular stenosis can occur, therefore superior or inferior to the valve plane.

The causes of the aortic stenosis they can be:

  • senile calcification, calcific aortic valve is the most common finding, 75 % of patients over 70 years occurs in ca;
  • congenital: bicuspid valve;
  • William's syndrome, a genetic disease that mainly causes SSA (supravalvular aortic stenosis);
  • rheumatic fever, less common than in the past.

L'aortic valve area it is usually between 3-4 cm ^ 2, a narrowing equal to 1 cm ^ 2 is associated with a higher systemic pressure gradient which results in an increase in the load of the left ventricle and consequently in its mass. Concentric hypertrophy of the left ventricle, as a compensatory mechanism, can usually maintain ventricular function for many years without consequent reduction in output or the appearance of symptoms.

Aortic stenosis is usually diagnosed only when it becomes symptomatic, because for a long time the ventricle is able to compensate for the pressure increase due to stenosis without giving obvious symptoms of overload.

The compensation mechanism of the stenosis involves, due to the increase in the pressure gradient between the left ventricle and aorta, a definite increase in muscle mass concentric hypertrophy of the left ventricle which has the consequence:

  • increased need and consumption of myocardial oxygen;
  • reduction in coronary reserve and diastole time, with increased risk of ischemic heart disease without underlying coronary artery disease;
  • left atrial hypertrophy with risk of AF onset due to increased ventricular diastolic pressure.

In the clinical setting, a patient with aortic stenosis is usually a patient over the age of sixty with ache to the chest, dyspnea from effort or syncope. As the disease progresses, it may encounter a left heart failure, with appearance of orthopnea ed pulmonary edema.

The key examination that allows us to diagnose aortic stenosis is the echocardiogram that depending on certain parameters such as:

  • AVA (Aortic valve area, normal value between 3-4 cm ^ 2), the flow velocity through the valve (vn 1-2.5 m / s)
  • MPG (medium gradient, vn <5 mmHg) allows to classify the stenosis in mild, moderate or severe.

Aortic stenosis treatment

There is no medical treatment for aortic stenosis that can avoid surgery for the patient. It is necessary replace there aortic valve.
Therapy with Ace inhibitors and diuretics improves symptoms and allows the patient to reach the operation in conditions that are as optimal as possible.

In a symptomatic patient there is a prognosis of 2-3 years without surgery, if the patient already has symptoms of decompensation the prognosis is reduced to one year. Even in an asymptomatic patient, if the presence of severe stenosis is detected on the echocardiogram, there is an indication to perform surgery.

In case of aortic stenosis it is not certain that one must necessarily undergo major open heart surgery, but if the patient's clinical condition allows it and the age above 75 years, one can undergo a transcatheter valve replacement surgery called TAVI.

The term TAVI stands for "Transcatheter Aortic Valve Implantation" that is a replacement of the transcatheter aortic valve, sometimes it is also found with the words TAVR "Transcatheter Aortic Valve Replacement".
It is a minimally invasive surgical procedure of percutaneous replacement of the aortic valve, without removal of the same, but with the implantation of a metal stent inside which the cusps of the biological prosthesis are located. The stent holds in position the bioprosthesis that begins to function as a natural aortic valve.

How do you proceed?

There are several approaches by which the cardiologist hemodynamist or the heart surgeon may choose to implant the new valve.

The common denominator in all cases is the introduction of a catheter through guides equipped at the end of a balloon deflated and a device for releasing the new valve. At the beginning of the procedure, the calcified aortic valve is reached through a transapical or transfemoral approach, a first balloon expands, unblocking the narrowing of the diseased valve and after withdrawing it inflates a second balloon, the one with the metal stent inside which the cusps of the biological aortic valve are found.

The operation is usually performed under local anesthesia, under constant radiological control, in fact there is the injection of a contrast medium to visualize the vessels. Two accesses are possible as we said:

  • transfemoral: from the femoral artery it goes up with the catheter up to the aorta through the abdominal artery;
  • transapical: through the right minithoracotomy the cardiac apex is accessed and with guides and catheters it is possible to reach the aorta.

An interesting aspect of the TAVI / TAVR is the possibility of applying this procedure even in the case of stenosis arising on a valve prosthesis, in this case we speak of a procedure called "valve in valve".

Up to three can be encountered over the course of a lifetime interventions of TAVI / TAVR. In fact, with the TAVI there is the implantation of a biological valve that we remember has a duration of approximately ten years. Nowadays, this procedure is reserved for those people who have an intermediate risk undergoing open heart surgery. For this reason, most people who have this procedure are between the ages of 70 and 80 with various comorbidities that make them perfect candidates. TAVI can be a valuable alternative for patients who have limitations for repairing their aortic valve.

We will describe the possible surgeries on the aortic valve immediately after addressing the other very common pathology of the aorta: insufficiency.

Aortic valve insufficiency

The term aortic insufficiency indicates retrograde blood flow into the left ventricle from the aorta as a result of an incompetent aortic valve. Prevalence is 5-10 % and increases with age.

Incompetence of the valve can result from pathologies affecting the valve flaps or the root or ascending aorta. It should also be remembered that there are two types of aortic insufficiency: acute and chronic aortic insufficiency which, although they affect the same valve, are to be considered as distinct entities for causes, presentation and treatment.

Causes of acute aortic insufficiency:

  • Diseases affecting the valve:
    • infective endocarditis
    • thoracic trauma
  • Injuries of the valve wall:
    • aortic dissection
    • aortic aneurysm

Causes of chronic aortic insufficiency:

  • diseases affecting the valve:
    • rheumatic endocarditis
    • congenital malformations: interventricular septal defects, congenital bicuspid valve
  • wall pathologies:
    • Syphilis
    • Marfan syndrome
    • Ankylosing spondylitis
    • Reiter's syndrome
    • Rheumatoid arthritis
    • Systemic lupus erythematosus

While previously with aortic stenosis we saw that the symptoms resulted from concentric hypertrophy of the left ventricle due to pressure overload, we will now see how in aortic insufficiency the incompetence of the valve leads to an increase in volume with the appearance of symptoms due to expansion of the left ventricle accompanied only in the most advanced cases a hypertrophy.
By combining dilation and hypertrophy we will have a patient with the so-called "cor bovinum " or bovine heart.

The patient may remain asymptomatic for a long time or sometimes report palpitations, but when the ventricle begins to fatigue there is the appearance of the first symptoms severe:

  • exertional dyspnea
  • paroxysmal nocturnal dyspnea
  • angina
  • orthopnea
  • profuse sweating.

Also in this case the examination that comes to our aid and allows us to evaluate the insufficiency is the echocardiogram that according to the ratio between the reflux area / LVOT (left ventricular outflow tract) allows to divide the aortic insufficiency into mild, moderate and severe.

Treatment of aortic insufficiency

The primary purpose of medical therapy is to reduce systolic hypertension (cause of left ventricular remodeling)
ACE inhibitors are also useful.
It is useful in milder cases to carry out an echo every 6-12 months to monitor the progress of the insufficiency.

Directions to surgery:

  • increased symptoms,
  • enlarged heart on x-ray or echocardiography,
  • treatment-refractory infective endocarditis

The goal is to replace the valve before severe left ventricular dysfunction occurs.

Predictors of poor survival post-operative are:

  • FE <50%
  • NYHA III-IV
  • duration of congestive heart failure> 12 months

For aortic insufficiency until some time ago it was possible to perform an operation, called Ross surgery, which consists of a surgical operation where a diseased aortic valve is replaced with the pulmonary valve of the same patient. The missing valve is replaced with that of a corpse (in this case we speak of an allograft).

Aortic valve replacement

During this surgery the damaged heart valve is removed and replaced with an artificial aortic valve.

This is an open heart surgery, under general anesthesia.

During an open heart surgery, the surgeon makes a long incision along the breastbone. The blood instead circulates outside the body through a machine that adds oxygen (we are talking about the cardiopulmonary bypass or heart-lung machine).
The heart can be cooled to slow it down or stopped, thus protecting it from possible damage from surgery.
There are two types of valves available to the heart surgeon: biological and mechanical.

Mechanical aortic valve life

The mechanical aortic valve is usually chosen in patients under the age of 65 who will then have to follow anticoagulant therapy (Coumadin or new oral anticoagulants) for the rest of their life.

Biological aortic valve duration

For patients over the age of 65, a biological valve (often coming from the pig) is usually chosen which will not require life-long anticoagulant therapy, but will be replaced every ten years due to progressive degeneration.

What to expect after surgery?

Hospitalization does not have a well-defined period, it varies from patient to patient and immediately after the intervention includes a monitoring period even in intensive care. You will probably need to take 4 to 12 weeks off work after your heart surgery.

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