Valvular surgery concerns primarily the aortic and mitral valves. Aortic regurgitation in the elderly, aortic regurgitation of infectious or degenerative origin and mitral regurgitation justify surgery whenever the clinical, ultrasound and haemodynamic criteria no longer are within normal limits. Whenever a cardiac valve does not function normally, depending on the disorder, it can be repaired or replaced.
Prior to surgery, patients are out of breath, the heart is exhausted and attempts to compensate for valvular stenosis or regurgitation. Echocardiography makes it possible to assess the damage to the valves and to determine the type of surgery necessary in the short- or long-term. Valvular heart disease requires “open heart” surgery, which is facilitated by means of ECC (extra corporeal circulation).
We have seen remarkable progress in valvular surgery over the last two decades. Thus, valvular heart disease can be treated either by valvuloplasty, implantation of a ring which restores the shape and function to the valve or its replacement by a mechanical or biological artificial valve.
1-ADVANCES IN PROSTHESES.
Replacement of a stenotic or leaky valve by a prosthesis is routine surgery.
Advances have been made, not only in design and shape of valvular protheses, but also the tissue materials used. To date, two major types of prosthetic valves exist to repair a defective valve: mechanical prostheses and biological protheses, most often of animal origin.
Mechanical valves are the oldest type. They have widely demonstrated their reliability regarding efficacy and tolerability.
Mechanical valves last as long as the patient’s lifespan and are changed only in case of a complication, which is very rare.
Their disadvantage is that they require life-time use of closely monitored anti-coagulant treatment.
A mechanical prosthesis consists of two components:
– a metallic insertion ring which fastens the prothesis to the mitral or the aortic valve;
– a movable component manipulated by the effect of pressures in the chambers of the heart on each side of the prosthesis; and
– on the prosthesis enabling it to open and close.
Different types of mechanical valves exist: the ball valve, the tilting single disc valve and the tilting double disc valve.
A valve consisting of a ball which is lodged in a metallic cage whose ends are open; with the purpose being that one of the ends can close depending on contraction of the heart which makes the ball rise or descend. This type of valve is intended to replace diseased valvular orifices (aortic and mitral valves).
Tilting single disc valve:
A type of prosthetic valve consisting of a single disc which enables the valve to open when it tilts. This valve consists of a cobalt-chromium alloy disc covered by white Teflon in which a pyrolytic carbon bi-leaflet valve which oscillates between two struts.
Tilting double disc valve, or so-called bi-leaflet valve:
Type of prosthetic valve consisting of two discs on an axis. Their excellent haemodynamic performance and longevity make them reference valves.
The different “bi-leaflet” valves are described below:
Biological valves or bioprostheses:
Bioprostheses are a second major group of valves.
Currently, two types of bio-prostheses exist, those with an armature and those without an armature.
The major advantage of these biological prostheses is that the patient does not require long-term anti-coagulant treatment. Moreover, they carry a lower risk of complications.
But, on the other hand, this type of valve deteriorates with time, requiring some patients to undergo repeat surgery. They deteriorate more quickly in a young patient and it is for this reason that the surgeon will decide to implant them preferably in the elderly, patients over 75 years of age. Two types of bioprostheses exist: heterografts (of animal origin) and homografts (of human origin). But in the majority of cases, we use heterografts.
These are aortic, mitral and pulmonary valves collected from humans, living donors whose heart has been collected during explantation prior to cardiac transplantation or from persons whose valves are removed at time of death and then are processed and sterilised.
Lastly, they do not require anti-coagulant treatment, but their available in sufficient number for treatment of the number of patients with valvular heart disease.
Replacement of the aortic valve with a homograft accounts for only about 3% of cases in the treatment of acute aortic endocarditis and is used mainly for young patients, and for women of child-bearing potential.
Its major disadvantage is extensive and very frequent calcification.
In a synthetic ring attached with a dacron cloth on a frame, porcine or pericardial sheep valves are implanted.
Currently, there are three types of prostheses with a metal frame, with a flexible armature or with no armature.
Bio-prosthesis with an armature:
Bio-prostheses with an armature account for almost 90% of cardiac valves implanted.
Porcine bioprotheses implanted are 2nd generation valves with optimisation of the process of manufacture to limit calcifications.
PERIMOUNT Carpentier-Edwards aortic valve: pericardial cardiac valves of animal origin with an armature.
One of the porcine valves processed and mounted on a rigid support, a type of prosthetic valve widely implanted for about the last 20 years.
Xenogenic stentless valve without an armature :
This type of prosthesis makes it possible to gain in size compared to those with an armature and they have increased longevity.
They are developed based on two principles, improvement of haemodynamic performance.
Medtronic Freestyle Stentless valve in aortic position.
Porcine natural valve, without sectioning, without reconstruction, but reinforced at the base for implantation.
These valves improve haemodynamic performance.
Durability of this prosthesis in subjects 30 to 60 years of age justify its use, providing good quality of life to patients.
Xenogenic valve with a flexible armature:
MITROFLOW PERICARDIAL VALVE
A prosthesis made of bovine pericardium and mounted on a flexible support medium
These pericardial bio-prostheses are made from bovine or equestrian pericardial tissue. They approximate the aortic valve with three semi-lunar valves mounted on a flexible armature.
Edwards Sapiens and Corevalve valve.
A innovative surgical approach has been adopted in recent decades with implantation of aortic valves correlated with techniques of endovascular catheterisation.
The introduction of these so-called peri-cutaneous valves into surgery provides new models of prostheses using new means of attachment and based on the principle of stent placement with a memory of shape.
The Sorin Solo valve (Sorin Solo stentless valve, without a support medium)
generally is implanted on the wall of the aorta with a single line of sutures.
2-ADVANCES IN SURGICAL TECHNIQUES.
We have seen significant advances in surgical techniques over the past 20 years, such as mini-thoracotomy, but the true revolution comes from two methods which are the TAVI (TAVI: “Trans Arterial Valve Implantation”) and, more recently still, TMVI (TMVI: “Transcatheter Mitral Valve Implantation”). These last two procedures are performed by percutaneous approach, without anaesthesia and with no surgical incision.
MINI STERNOTOMY AND SUTURELESS AORTIC VALVULAR PROSTHESES
With regard to the mini incisions, mini sternotomy and mini-thoracotomy are techniques that have become widely used for two reasons. Firstly, they are less invasive for patients who are increasingly older and frail, therefore carrying higher surgical risk, secondly, the technical possibility of using a prosthesis with “rapid deployment”, such as the TAVI (Sorin Perceval valve); see photograph.
Surgical replacement of the aortic and the mitral valves by mini-thoracotomies improves the patient’s quality of life. They mean we can avoid a complete median sternotomy and reduce surgical trauma by decreasing the size of the incision and facilitate post-surgical follow-up. The combination of a mini sternotomy and of a sutureless valvular prosthesis (without sutures) and of its rapid deployment have provided a true gain in time and simplification of open-heart conventional aortic valvular surgery. The major advantage of this technique compared to TAVI is the possibility of excision of a calcified valve, thus enabling complete deployment of the prothesis.
The second advantage of this simplified technique is to treat coronary or other valvular lesions.
It is therefore possible to perform aortic implantations in 20 minutes as opposed to up to 50 minutes. The combined use of a sutureless prosthesis with CABG on a beating heart with ECC (Pump Off) enables us to perform an impressive procedure, in the elderly, 2 to 3 CABG on a beating heart together with aortic valve replacement in about only 20 minutes of ECC and clamping of the aorta.
Therefore, the post-surgical follow-up is less complicated in terms of pain, major blood loss and risk of transfusion and also duration of hospital stay is shortened. Convalescence is reduced, the patient can resume his or her activities more quickly. And without mentioning the improved cosmetic presentation!
 CABG: Coronary artery bypass grafting