Aortic Valve

Heart valves open and close to allow the blood to flow in and out of the four chambers of the heart in the right direction. If they are damaged through infection (also called endocarditis) or disease they will either not open properly, and become stenotic or not close tightly enough, and leak. Both problems mean the heart has to pump harder. A new aortic valve relieves the strain on the heart and aims to ease symptoms such as breathlessness and chest pain.

The severity of the valve disease is based on physical examination and the echocardiographic  findings. The indications for intervention are based on the following:

  • the presence or absence of symptoms,
  • the  severity of valvular dysfunction,
  • the  response of the heart to he presence of valvular disease (dilatation, hypertrophy, failure),
  • the effect on the pulmonary or systemic circulation, and
  • the changes in heart rhythm.

All patients with heart valve disease are assigned to one of the new 4-stage.

  • A (at risk)
  • B (progressive)
  • C (asymptomatic severe)
  • D (symptomatic severe)

Bicuspid (bileaflet) aortic valve (BAV)

Bicuspid (bileaflet) Aortic Valve disease (the disease where the aortic valve has two instead of three cusps (or otherwise known as leaflets) is also a heritable disorder, is known to have an increased risk of ascending aortic aneurysm as well. Bicuspid aortic valve (BAV) disease is the most common congenital cardiac disorder, being present in 1-2% of the general population. Approximately 9% to 15% of first degree family members also have BAV disease, with men and women equally affected within family members. Therefore, it is recommended that first-degree relatives of patients with BAV are screened with echocardiography

In BAV disease, valvular complications (aortic valve stenosis or regurgitation) progress at their own independent rates, different from the rate of progression of the bicuspid aneurysm. Patients with pure/predominant BAV aortic regurgitation (10% to 15% cases of BAV) tent to be younger and males.

BAV aortopathy and aortic aneurysm is a common finding in patients with BAV disease and as high as 40%. Aneurysmal dilatatation in BAV aortopathy may occur in the aortic root, the tubular ascending aorta (most common, 60-70%), the proximal aortic arch, or any contiguous combination of these three. Although only 5% or less of patients with BAV will have aortic dissection over a lifetime, so BAV is an important cause of aortic dissection. Patients with BAV and aortic valve disease (stenosis or regurgitation) are at increased risk of rupture and dissection of the aorta. Evidence increasingly demonstrate that BAV with aortic regurgitationcan be more malignant phenotype than BAV with aortic stenosis BAV, with a higher risk (10x) of aortic dissection.

BAV pathologyBAV aortopathy consists of premature changes to the consistency of the aortic wall (cystic medial degeneration) in approximately one half of the patients who had surgery for BAVs. Valve mediated blood flow dynamics and regional wall stress differences are associated with changes in regional aortic wall histology and proteolytic events which are known to contribute towards the premature changes to the consistency of the aortic wall. Both genetic predisposition and rheological abnormalities may coexist, resulting in diverse clinical presentations, with distinct natural histories.Patients with BAV often present at a younger age, interventions should aim for the strategy that provides the best long-term benefit. Experienced surgeons faced with patients having BAV dysfunction and an ascending aortic aneurysm of 4.5 to 5.0 cm are supported in an open approach (especially for for low-risk patients), rather than isolated aortic valve therapies with transcatheter aortic valve implantation (TAVI) alone. This is especially true if aortic dissection risk factors (family history, root phenotype, growth ≥0.3 cm/y)  or aortic regurgitation are present.

Indications for Elective Surgical Repair of DilateAscending Aorta/Aortic Root/Aortic Arch Associated With Bicuspid aortic valve (BAV) 
  • Repair of the ascending aorta/root is recommended when:
    • The diameter is >5.5 cm in patients with no risk factor
    • The diameter is ≥50 mm and no risk factors, when the patients are at low surgical risk and operated on by an experienced aortic team in a center with established surgical results.
    • The diameter is <5.0 cm associated with any of the following:
      • Root phenotype or predominant aortic valve regurgitation,
      • Uncontrolled hypertension,
      • Family history of aortic dissection/sudden death,
      • Aortic coarctation,
      • Aortic diameter growth >3 mm/y
      • Small adult body size (especially if they have Turner’s syndrome), indicated by either of the following:
        • aortic cross-sectional area to height ratio of > 10 cm2/m
        • Indexted aortic diameter of >2,75 cm/m2
      • Women planning pregnancy because of an increased risk of aortic complications in such patients
      • Patients with BAV aortic regurgitation and root phenotype of aortic dilation at an aortic diameter of 5.0 cm. Such patients may particularly benefit from a valve-sparing aortic root replacement (David) operation, if done in an experienced center with known outcomes.
  • Concomitant repair of the ascending aorta/ root should be performed when the aortic diameter is ≥45 mm in patients undergoing cardiac surgery.
  • Repair of the aortic arch is recommended:
    • When the aortic arch diameter is ≥55 mm.
    • Concomitantly for patients undergoing cardiac surgery for other reasons and have an aortic arch diameter of ≥50 mm
    • Concomitantly for patients undergoing cardiac surgery for other reasons and have aortic arch diameter of ≥45 mm, provided the patients are at low surgical risk and operated on by an experienced aortic team with established surgical results.
    • For patients undergoing elective aortic arch repair by an experienced aortic team with established surgical results.

Surgery to the aortic valve

The reasons for aortic valve intervention are: to improve symptoms, to prolong survival, and to reduce the risk of complications. The operation involves replacing a damaged valve in your heart with a mechanical valve (made from man-made materials) or a tissue valve (usually from a cow or pig). requires a hospital stay of 5-7 seven days and is done under general anaesthesia. This means you will be asleep during the procedure. Once the anaesthetic has taken effect, your surgeon will make a cut (traditionally about 25cm long, mini sternotomy about 10-12cm long), down the middle of your breastbone and open the ribcage to reach the heart. The heart is slowed or stopped (using medication) and blood is re-routed to a heart-lung machine. This takes over the pumping action of the heart and lungs, adding oxygen to the blood and maintaining the circulation.

Your surgeon will open the heart chamber, remove the faulty valve and sew in a replacement. Blood is then redirected back to your heart and the heart is restarted. The breastbone is re-joined using wires and your chest is closed using dissolvable sutures, stitches or staples. The operation usually takes about 2-3 hours.

 Aortic valve replacement is one of the commonest procedures performed in cardiac surgery. The stented biological or mechanical prostheses (“tissue” or “metal” valves) that are used always require the insertion of sutures for their implantation. The reason for this is to bring the tissues of the aortic annulus (compliant part) to the aortic valve prosthesis (non-compliant part). During this process, the choice of selected valve (new door) is marginally smaller than the actual annulus (door frame), where it is due to be implanted; the sutures are there to make sure that this gap is closed. Rapid deployment biological valves (sutureless) are new valves that use established, self-expanding stent technology (already used in other products such as vascular stents and TAVI valves) that allows for the valve to self-expand after deployment, meet the aortic annulus, and provide adequate radial force to keep the valve in place, without the need for sutures.

On certain occasions and usually for very young patients the Ross procedure can also be offered, which consists of full replacement of the aortic root (valve and aortic wall), replacement of the of the extracted tissues with the patients own pulmonary artery with the valve and replacement of the pulmonary artery and the valve used with a homograft (artery and valve from another human).

Biological valves for aortic valve replacement

There are a variety of biological valves which can be used for aortic valve replacement. Most are made from cow or pig tissue and they use sutures to attach them to the heart. The main advantage of this type of valve is that it is associated with a low risk of blood clot formation which if occurs, can cause the valve to malfunction or cause a stroke. The main disadvantage is that these valves have a limited durability as compared with mechanical valves. In other words, they will wear out given enough time. The rate at which they wear out depends on the patient’s age. A young boy might wear out a valve in only a few years, while the same valve might last 10-15 years in middle aged person, and even longer in a patient over the age of 70. The general consensus is that a tissue valve is best used in patients from the age of >60 years.

New technology sutured bovine bioprosthetic valves claim that they can offer longer durability due to better decalcification process and build-in technology for future valve-in-valve TAVI procedures and as such, they could be offered to patients of <60 years of age. The Edwards Inspiris Resillia valve has demonstrated very good durability and hemodynamic performance after an equivalent of 25 years of simulated in vitro accelerated wear testing, however hard evidence to support this statement are still missing due to the fact that this technology is new and longterm durability data are still awaited.

There are some bovine (cow) tissue biological valves that are mounted onto a stent and they do not need any sutures during surgery. They are known by the name of suturerless or rapid deployment valves. By not using sutures during the operation, the time that the heart is exposed to unfavorable conditions (ischaemia) can be reduced by 50%, which could translate into better clinical outcomes, and faster recovery. The absence of a sewing ring allows for a bigger valve size to be implanted within the given aortic annulus dimensions (when compared to the currently used sutured equivalent). This is associated with better haemodynamic performance, especially in patients with smaller aortic roots. The ease of implantation allows for smaller incisions and minimally invasive surgery that, in addition to a superior cosmetic result, could result in improved clinical outcomes in selected patients. Finally, the valve design facilitates a future TAVI through the Perceval valve, should that become necessary, by providing navigation landmarks and allowing for bigger TAVI valves compared to stented valve-in-valve procedures. Patients with aortic valve stenosis who opt for a bioprosthesis (“tissue” valve) can have the Perceval valve. This valve is probably better suited to patients older than 55 years of age, complex reoperations of the aortic valve, multiple procedures that include aortic valve replacement or in special circumstances that dictate its use due to technical issues during surgery. Patients with a bicuspid aortic valve or a dilated aortic root are not eligible and should preferably receive ‘conventional’ stented aortic valve replacement. Patients with known allergy to nickel alloys should also not receive this type of valve.

All patient with failing existing (surgically or percutaneously implanted) biological valves can become candidates for redo aortic valve replacement surgery or more often nowadays, for “valve-in-valve” percutaneous implantation of a new biological valve, within the existing failing prosthesis.

Mechanical valves for aortic valve replacement

There are a number of excellent mechanical prostheses available today. All perform equally well. The principle advantage of mechanical valves is their excellent durability, made from carbonised metal they simply do not wear out! Their main disadvantage is that blood cells are likely to form clots on the surface of the metal. If this happens the valve will not function normally. Patients with these valves must therefore take anticoagulants (blood thinners) for life. There is also a small but definite risk of blood clots causing stroke, even when taking anticoagulants.

Aortic valve repairs

Aortic valve repair is a new way of treating dysfunctional aortic valves. Not all leaking aortic valves are amenable to aortic valve repair and not all cardiac surgeons are capable in performing this type of operations. It is recommended that aortic valve repairs are performed by sub-specialist aortic surgeons with specialist interest in the field.

AV repair.techniques and mechanism

Tricuspid aortic valve (the aortic valve has three doors, normal configuration) that present with aortic regurgitation (leaking valves) can be treated using a number of different type of techniques with  very good record of success and excellent functional end-result.

                      AV reapir 1      AV repair 2

Aortic valve repair can also be deployed into young patients with congenitally abnormal aortic valve (defects you are born with) like the bicuspid aortic valve (the aortic valve has two doors). The aortic valve repair of those valves can offer to the patient a functionally competent valve with excellent haemodynamics  and postpone the replacement therapy into the future.

BAV repair

Here are some procedures surgeons may use to repair your aortic valve:

  1. Commissurotomy, which is used for narrowed valves, where the cusps (the leaflets that make up the valve) are thickened and perhaps stuck together. The surgeon opens the valve by cutting the points where the cusps meet.
  2. Valvuloplasty, which strengthens the cusps to provide more support and to let the valve close tightly.
  3. Reshaping, where the surgeon cuts out a section of a cusp. Once the cusp is sewn back together, the valve can close properly.
  4. Decalcification, removes calcium which has built up on the cusps. Once the calcium is removed, the cusps can close properly.
  5. Patching, where the surgeon covers holes or tears in the cusps with a tissue patch.

Percutaneous options for aortic valve disease – TAVI or TAVR

TAVI1

Different TAVI valvesThis minimally invasive surgical procedure treats the malfunctioning valve and alleviates the symptoms without removing the old, damaged, native aortic valve. Instead, it wedges the new valve inside the old, diseased valve, which has been previously stretched open.

The surgery may be called a transcatheter aortic valve replacement (TAVR) or transcatheter aortic valve implantation (TAVI). These techniques are reserved for patients who are well over 70 years of age (usually in their 80s & 90s) and who either cannot have or who carry a very high risk of death from formal cardiac surgery. As a TAVI is still a new procedure, its long-term benefits are not known. At present, if you need to have an aortic valve replacement, it is more likely that you will be offered a conventional heart valve surgery.

tavi-steps

 The Oxford TAVI Team have been working together since the inception of the technology in 2009 and is delivering hundreds of TAVI operations per year.  Every case that is refereed for TAVI is discussed at our sub-specialised TAVI multidisciplinary team and the treatment options are individualized and optimized to meet the needs of each and every patient we treat.

When transcatheter aortic valve implantation (TAVI) is performed transfemorally, via the grointavi-transfemoral-oder-transapical, a local anesthetic is used to numb the area around the artery in order to insert a special catheter. Once inside the artery, the catheter is advanced from the groin to the aortic valve of the heart. This catheter carries an expanding valve armed with a specially designed balloon. After the new valve is implanted within the existing (native) valve, the patient returns to a high dependency area for observation. The patient usually leaves the hospital within 2-3 days after surgery.

When we are replacing the aortic valve through a small incision in the chest – transapically or transaortic, a general anesthetic is given to the patient. After a small incision has been made to the left side of the chest, a special catheter is advanced from the apex of the heart to the aortic valve. This catheter carries an expanding valve armed onto a special balloon. After the new valve is implanted within the native valve, the patient returns to a high dependency area for observation. The patient usually leaves the hospital within 3-5 days after surgery.

 

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Valves of the heart         Aortic valve problems        Aortic valve replacement      TAVI Implantation 

   

 

    

 

Links:These, like any other published guidelines & evidence, do not and should not override the individual responsibility of healthcare professionals to make appropriate decisions in the circumstances of the individual patients, in consultation with that patient, and where appropriate and necessary the patient’s guardian or carer. 
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