Generality
Aortic valve replacement is a delicate, open-heart surgery to replace a no longer functional aortic valve with a prosthesis. The latter can be mechanical or biological and the choice of one or the other depends on the age of the patient.
The valve replacement operation is required in two pathological circumstances: in cases of aortic stenosis and in cases of aortic insufficiency.
Although it is an effective intervention, replacement of the aortic valve can, in certain circumstances, cause complications or be poorly indicated. In the latter case, alternative surgical treatments are used.
Brief anatomical reference: the heart and heart valves
The heart is composed of two halves, right and left. The right half is formed by the right atrium and by the underlying right ventricle . The left half is formed by the left atrium and by the underlying left ventricle .
Each ventricle has two valves with a particular anatomy:
- The right ventricle has
- the tricuspid valve, which controls the incoming blood coming from the right atrium
- and the pulmonary valve, which allows the blood to escape and reach the lungs.
- The left ventricle possesses
- the mitral valve, which controls the incoming blood coming from the left atrium
- and the aortic valve, which allows blood to flow out and flush the body's tissues and organs.
The valves therefore control the passageways of the blood, functioning as gates. To do this, they use special structures, called flaps or cusps, which can open and close as needed.
THE AORTIC VALVE
The aortic valve is the valve that allows oxygenated blood to pass from the left ventricle to the aorta, through which it will be distributed to the tissues and organs of the body. It is formed by three flaps.
Aortic valve replacement
Aortic valve replacement is an open-heart surgery that is performed when the aortic valve is defective and no longer works properly.
The valve prostheses that are implanted when there is a valve defect, can be of two types:
- Artificial or mechanical . They consist of a particular material, pyrolytic carbon .
- Advantages: remarkable resistance and long life. Recommended for younger patients.
- Disadvantages: blood clots may form on the valve surface. These clots could give rise to a stroke (see the chapter on risks).
- Biological . They consist of animal tissue, usually bovine or equine pericardium .
- Advantages: there is less danger of blood clots forming.
- Disadvantages: they are less durable, so they are not recommended for younger patients.
When needed
Aortic valve replacement surgery is basically performed for two reasons:
In case of severe aortic stenosis . The restriction (stenosis) of the aortic valve is meant; this narrowing prevents the blood from flowing normally through the valve itself.
Mild / moderate cases are monitored and do not require immediate intervention.
- In case of severe aortic insufficiency . An anatomical defect of the valve is meant, which causes the blood to flow back, from the aorta to the left ventricle.
Mild / moderate cases are monitored and do not require immediate intervention.
Stenosis and aortic insufficiency are two conditions that can be both congenital (ie present from birth) and acquired (ie developed over the years).
| Main diseases that cause aortic valve anomalies | |
Congenital:
| acquired:
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SYMPTOMS
The symptoms, which arise due to a defective aortic valve, do not appear immediately, but only when the causative pathology is at an advanced stage. An early diagnosis can therefore have significant benefits and make the prognosis positive.
Figure: a normal aortic valve compared to an aortic valve affected by stenosis (or stenotic). From the site: www.bigappleheartsurgery.com
The classic manifestations are: chest pain ( angina pectoris ), shortness of breath, dizziness / vertigo and loss of consciousness .
The cause of the entire symptomatology is only one: the reduced capacity of the heart to pump blood to every part of the body.
How is the surgery performed?
ANESTHESIA
Aortic valve replacement surgery is performed under general anesthesia . This means that the patient is not conscious and does not perceive any pain during the operation.
THE "OPEN HEART"
Once the anesthesia is practiced, a thoracotomy is performed, that is the opening of the chest, in order to have free access to the heart to be operated.
EXTRACORPARE CIRCULATION
At this point, the surgeon must isolate the heart from the circulating blood and, to do so, resort to the so-called extracorporeal circulation ( CEC ). The CEC consists in the deviation of the afferent and efferent vessels of the cardiac organ towards an instrument, called the heart-lung machine . This machine effectively replaces a human heart; in other words, it takes care of oxygenating the blood and sending it into circulation, thus not compromising the patient's vital functions.
REPLACEMENT
The heart, now, is like it was off and only then is one ready to replace the faulty aortic valve. The latter is removed, being careful not to damage the rest of the cardiac structure, and replaced (by suture) by a mechanical or biological prosthesis.
CONCLUSION
After the graft of the new valve, the normal anatomy of the blood vessels is restored and an electric shock is infused into the heart, to restart it.
DURATION OF THE INTERVENTION
The replacement of the aortic valve, but in general all open-heart procedures, are very long operations, which can last from 4 to 5 hours.
risks
The intervention is not without risks. About 1 person in 50 dies after the valve replacement or due to the complications that may arise from it.
Nevertheless, it is always advisable to resort to the operation, as stenosis and aortic insufficiency, if not treated, make many more victims.
THE COMPLICATIONS
The list of possible complications includes the following circumstances:
- Infections and inflammatory states ( endocarditis ). Infections, if left untreated, can degenerate and impair cardiac activity. They are treated with antibiotics.
- Embolism . It occurs especially when the prosthesis is mechanical. To avoid this, the patient should take oral anticoagulants.
- Stroke or transient ischemic attack ( TIA ). It is a possible consequence of embolism.
- Wear of the valve prosthesis . It occurs more often with biological prostheses.
- Arrhythmias . They afflict about 25% of people subjected to surgery.
- Renal failure . It occurs in 3-5% of operated individuals.
Alternative interventions
The replacement of the aortic valve is the first choice intervention when a serious defect of this valve is detected.
However, when the open heart operation is not recommended (for example due to the precarious health condition of a patient), one is forced to resort to alternative surgical treatments; these include transcatheter aortic substitution, aortic valvuloplasty and aortic replacement without stitches .
These alternative surgical methods are less invasive, but also less effective and at higher risk of post-intervention complications.
TRANSCATETER AORTIC REPLACEMENT
The surgeon "hooks" the new valve to a catheter and leads it to the heart in two possible ways: either through the large vessels or through an incision in the chest.
Once the heart is reached, the surgeon "releases" the valve prosthesis over the old one and extracts the catheter, which at this point is no longer useful.
It is a new surgical technique, which must be perfected.
A person in about 15-16 years, after this surgery, experiences a stroke episode.
valvuloplasty
Aortic valvuloplasty is the enlargement of the narrow (or stenotic) aortic valve. It is performed using a catheter, which is inserted into the blood vessels and led to the heart.
Figure: transcatheter aortic replacement .
From the site: advancingyourhealth.org
It is an intervention particularly suitable for younger children, who are not yet ready for an open heart surgery.
The main drawback of valvuloplasty is the fact that after two or three years it must be repeated, or replaced by another intervention.
AORTIC REPLACEMENT WITHOUT SUTURE POINTS
It is an innovative surgical technique. During the operation, thoracotomy and the use of the heart-lung machine are practiced, but, unlike the classic valve replacement, the application of the new aortic valve is performed without the use of sutures . This greatly shortens the duration of the operation and the time of extracorporeal circulation, to which the operated patient is forced.
The method must be perfected, as the valve is not always fixed adequately and in a stable manner; once this problem has been solved, however, this new procedure could probably replace the traditional one of replacing the aortic valve brilliantly.
