Heart valve replacement

The basic principles of technique and tactics of implantation of frame bioprostheses are similar to those when using mechanical valves. Unlike mechanical and skeletal biological prostheses, frameless bio-valves (xenografts, allografts, etc.) are not rigid, resistant to deformation structures and therefore such a replacement of the heart valve can be accompanied by a change in both geometric and functional characteristics. How and how does the function of frameless bio-valves change as a result of implantation? What factors should be considered before and during the implantation of frameless heart valve replacements in order to preserve their original functional characteristics as much as possible? Which heart valve replacement provides the best functional outcome? The answers to these and other questions were tried in a number of experimental and clinical studies.

A comparison of the hydrodynamic characteristics of a Medtronic Freestyle prosthesis implanted in an elastic silicone "aorta" showed that the pressure gradient and the volume of regurgitation on the prosthesis largely depend on the size of the prosthesis and, to a lesser extent, on the variant of the implantation technique. The maximum opening areas of the flaps, measured during visualization of the prosthesis at the stand, were large when modeling the prosthesis using the "full root" method.

In subsequent works of other authors, the experimental model for assessing the effect of the size and technique of implantation of frameless bioprostheses on their functional characteristics in vitro has been improved. To do this, the frameless bioprosthetic implants were implanted into the native porcine aorta roots, and then also into the aortic porcine roots stabilized with glutaraldehyde. This, according to the authors, simulated implantation in the "young" and "elderly" roots of the human aorta.

In these studies, the replacement of the heart valve was accompanied by a significant decrease in the extensibility of native "young" aortic root-accepting roots, into which Toronto SPV frameless prostheses were implanted. The hydrodynamic parameters were better, and the flexural deformations of the open flaps were smaller when implanted with a Toronto SPV prosthesis with an outer diameter of 1 mm smaller than the inner diameter of the acceptor root. According to the authors, a moderately understated disparity in the implantation of xenografts can increase their wear resistance, depending on the deformation of the valve and flexural stresses. The hydrodynamic efficiency of the "young" composite aortic roots was significantly and significantly higher than the "elderly". Subcoronary replacement of the heart valve of both stabilized and native aortic roots led to a deterioration in their initial functional characteristics.

In the study, a comparative analysis of the functional results of experimental xenograft implantations in allogeneic aortic roots on embalming corpses of young and elderly people was carried out, followed by an assessment of the anatomical and functional characteristics of the removed composite aortic roots in poster trials.

A comparative analysis of the functional results of the two groups of composite aortic roots showed that the best biomechanical and hydrodynamic characteristics were obtained using a technique such as a subcoronary heart valve replacement with excision of all three sinuses of xenograft. With the preservation of the non-coronary sinus of xenograft, a paraprotease "hematoma" was often formed, significantly distorting the geometry of the composite root of the aorta and adversely affecting its flow characteristics and biomechanics of the valves. In clinical practice, the formation of paraproteinous hematomas in the area of the preserved non-coronary sinus xenograft often leads in the postoperative period to a high systolic pressure gradient that gradually regresses as the hematoma dissolves. With significant hematoma size and its further organization, high residual pressure gradients may persist or infection may occur with the formation of a paraprosthesis abscess.

The study also showed that the main factors influencing the functional outcome of such a procedure as replacement of the heart valve of the developed xenograft model are the acceptor root extensibility, adequate xenograft size selection and its position relative to the fibrous ring of the acceptor root. In particular, prosthetic aortic root does not affect the initial functional characteristics of the developed xenograft model. Supranannular subcoronary replacement of the heart valve, in contrast to the aortic root prosthesis, leads to the formation of moderate circumferential precomsural deformations of the xenograft flaps, and also provides him with better flow characteristics, in comparison with implantation in the intra-ananular position.

The choice of the technique of the operation in the case of using the frameless bioprosthesis in the aortic position is determined, first of all, by its design. A number of bioprostheses (AB-Composite-Kemerovo, AB-Mono-Kemerovo, Cryolife-O'Brien, Toronto SPV, Sonn Pencarbon, Shelhigh Standard and Shelhigh SuperStentless, etc.) are implanted only in the subcoronary position. Prostheses made as a whole xenogeneic root of the aorta (Medtronic Freestyle, PnmaTM Edwards) can be implanted into the subcoronary position with excision of two or three sinuses, and also as a root-inclusion with partial excision of the coronary sinuses of xenograft. Finally, these prostheses can be implanted according to the "full-root" technique. Most surgeons prefer to use the technique of subcoronary implantation using whole xenografts

In aortic prosthesis using the technique of subcoronary implantation, a transverse (2/3 perimeter of the ascending aorta slightly higher than the sinotubular junction) or an oblique, rarely complete transverse or semi-vertical aortotomy is most often performed. After careful excision of the valves of the aortic valve and the maximum removal of calcifications, the anatomical changes and geometry of the aortic root, the peculiarities of the location of the coronary arteries, are visually assessed.

The choice of the size of the frameless bioprosthesis remains controversial. Usually a bioprosthesis with a diameter of 1-3 mm larger than the maximum caliber that is sufficiently freely drawn through the aortic ring of the patient is selected. Sometimes a prosthesis with a diameter equal to the diameter of the aortic ring or the diameter of the sinotubular junction is selected, in some cases the root reconstruction is performed. With a low location of the right coronary artery, subcoronary replacement of the heart valve with a bioprosthesis reversal is applied, placing its right sine into the noncoronary sinus of the patient, or performing aortic root prosthesis. At the first stage of implantation of frameless bioprostheses in the supranannular subcoronary position on the fibrous ring, a proximal row of nodal sutures (3-0 ticron, 2-0 or 3-0 etibond, 4-0 lobule at the discretion of the surgeon) is superimposed in the plane of the ventriculoaortic joint, through the base of the fibrous ring. In the second stage, bioprostheses, which have been washed from the preservative and released as a whole root of the aorta, are prepared for implantation by excision of two or three sinuses of xenograft. Some authors do not recommend performing excision of sinuses at this stage, so as not to disrupt the spatial orientation of commissural columns at the next stages of implantation. Frameless bioprostheses produced with excised sines are not subjected to this procedure. In the third stage, the filaments of the proximal row of nodal sutures are passed through the base of the xenograft, taking care not to damage the valves with a needle. In the fourth stage, the xenograph is placed in the patient's aorta root, and the strings are tied and cut. To ensure the correct orientation of the commissure, impregnate U-shaped supporting sutures are placed 3-5 mm above the commissure of the xenograft, passing them through the aortic wall of the patient to the outside. The fifth stage of the operation can be performed in different ways, depending on the bioprosthesis model used. If a bioprosthesis model without sinuses is used or they were excised at the second implantation stage, then they are "adjusted" to the coronary arteries of the patient. At the same time, it is recommended to preserve the original spatial orientation of commissures and flaps.

Only after the suture orientation of the commissure is complete is the excess of the xenograft aortic tissue dissected. At the sixth stage of implantation, a continuous diagonal continuous wrap sealing seam is applied (4-0 or 3-0 prolen). The thread is drawn through the dissected margin of the xenograft sinus and the sine wall of the acceptor root below the coronary artery mouth. The distal suture begins to be applied at the deepest proximal point of the excised sine of the xenograft and ends at the top of the nearby commissures (sometimes it is recommended to start the distal seam in the opposite direction - from the top of the intercoronary commissure). The ends of the adjacent filaments are removed to the external surface of the aorta and linked together. In some cases, before the tying of distal suture filaments, fibrin glue is introduced into the paraprotease space between the non-coronary sinuses to avoid the formation of a paraprosthetic hematoma. It can be formed due to a mismatch between the sizes of the non-coronary sinuses of the bioprosthesis and the patient, and also become infected with the formation of a paraprosthesis abscess. The last stage of the operation consists in closing the aortotomous incision with a continuous suture (4-0 prolene). Some patients undergo aortic plasty with a native autopericardium or xenopericardium. The Cryolite-O'Brien bioprosthesis is fixed with a single-row (4-0-span) continuous suture into the supranannular position.

In the dilatation of the sinotubular junction and annuloaortal ectasia, the root-inclusion implantation technique is used in a number of cases. This technique consists in incomplete excision of the coronary sinuses and preservation of the sinotubular xenograft to ensure its initial spatial configuration. The proximal row of nodal sutures is superimposed according to the standard scheme. The coronary arteries of the patient are implanted into the adapted coronary sinus holes of the xenograft. The upper edge of the xenograft and the edge of the aorta-volume incision are stitched by a continuous polypropylene seam with simultaneous closure of the aorta.

Replacement of the heart valve according to the "full root" technique is performed much less often (at 4-15%) than the replacement of the heart valve in the subcoronary position. First, complete transverse aortotomy is performed slightly above the sinotubular junction. Then, cut out the mouths of both coronary arteries of the patient along with the prevailing portion of the sinuses, and then remove the affected valves of the aortic valve. Proximal anastomosis is imposed using 28-35 nodal seams (3-0), which are tied on a strip of teflon or native autopericardium 1 mm wide to seal the joints. The coronary arteries of the bioprosthesis are excised. Reimplant the mouth of the left coronary artery with a continuous continuous (5-0 cut) suture into the corresponding sinus of the bioprosthesis. Perform a distal anastomosis between the xenogram and the ascending aorta of the patient with a continuous suture (4-0 prolene) of the "end-to-end" type. At the last stage, the mouth of the right coronary artery is reimplanted.

It should be noted that technical errors or inaccuracies in the implantation of frameless bioprostheses can lead to their distortion, loss of mobility of one or more valves and, as a result, to the early development of structural degeneration and calcification. When implantation is necessary to constantly irrigate the bioprosthesis with saline solution to prevent drying and damage to the tissue of the valves.

The replacement of the heart valve of frameless bioprostheses in the aortic position is performed by patients with hemodynamically significant defects mostly older than 40 years or younger patients with intolerance to anticoagulants. Replacement of the heart valve of xenografts is performed, mainly, to patients aged 60-70 years and older. This type of bioprosthesis is the valve of choice for elderly patients and with a narrow aortic root (less than 21 mm) or with a low fraction of the left ventricular ejection, since the absence of a skeleton in the narrow root of the patient's aorta provides a high hemodynamic effect. Severe calcification of Valsalva sinuses, root aneurysm and / or ascending aortic anomalies in the location of the coronary arteries (proximity of the coronary artery to the fibrous ring of the valve or their location opposite to each other in the bicuspid valve), the presence of unrecognizable fibrous ring calcifications, significant dilatation of the sinotubular junction Contraindications to the implantation of frameless bioprostheses in the subcoronary position. The solution to this situation is the replacement of the heart valve of xenograft with aortic root prosthesis.

Normally, in young healthy people, the diameter of the sinotubular junction is always smaller than the diameter of the fibrous ring. However, in patients with aortic valve defects, especially in aortic stenosis, the diameter of the sinotubular junction often exceeds the diameter of the fibrous ring. In this case, the size of the bioprosthesis is selected according to the diameter of its sinotubular junction and implanted according to the "root insertion" technique or root prosthesis, or a subcoronary heart valve replacement is performed with the reconstruction of the sinotubular junction.

With an aneurysm of the root of the aorta, an isolated valve prosthesis is performed, either in combination with prosthetics of the ascending aorta, or a valve-containing conduit is implanted.

While singling out absolute contraindications to the use of frameless bioprostheses, some authors recommend refraining from their use in cases of active infective endocarditis. Other authors widely used bioprostheses Medtronic Freestyle, Toronto SPV with active infective endocarditis.

Some surgeons recommend implanting xenografts in the subcoronary position only in uncomplicated forms, when the infectious process is limited to the limits of the aortic valve flaps, since it is possible to infect the synthetic plating of the bioprosthesis.

More resistant to infection, according to some authors, have frameless bioprostheses trimmed with a stabilized pericardium. For example, shelhigh xenografts were used, mainly, in emergency cases in the absence of the required homograft size. The frequency of reinfection of frameless Shelhigh bioprostheses and homografts (4%) in patients of both groups was identical.

Usually in the postoperative period patients with frameless bioprosthesis are prescribed warfarin (MHO = 2-2.5) for 1.5-3 months. However, with the accumulation of experience, many surgeons prescribe warfarin to patients with atrial fibrillation and a high risk of thromboembolic complications. Individual authors prescribe only aspirin to those patients who additionally underwent aortocoronary bypass surgery.

Replacing the aortic valve with a pulmonary autograft using the DN Ross method (1967) is performed in patients with infective endocarditis of the aortic valve, with its congenital malformations, mainly in newborns and infants. There are several modifications to the operation of Ross - the replacement of the root of the aorta, the cylindrical technique, the Ross-Konn operation, etc. Also described is the Ross II operation, in which the pulmonary autograft is implanted into the mitral position. In the case of aortic root replacement technique, the ascending aorta is cut by transverse access and a revision of the aortic valve. The incision of the pulmonary artery is made transversely and below the level of the right pulmonary artery. The excision of the pulmonary artery root is performed carefully, so as not to damage the first septal branch of the left coronary artery. Both coronary arteries are cut off along with the sites from the surrounding tissue of the sinuses of Valsalva. The root of the aorta is excised at the level of the aortic ring along the lower edge of the walls of the aortic sinuses. The pulmonary artery trunk together with the valve is stitched with the base of the aortic root, and the coronary arteries are re-implanted into the autotraft. Allograft pulmonary artery is sewn to the opening of the outlet of the right ventricle and to the distal pulmonary trunk.

Frameless biological (allo- and xenogeneic) substitutes for atrioventricular heart valves have been developed and have so far been limitedly introduced into clinical practice with the aim of almost complete anatomical and functional replacement of natural valves in cases where the valve-preserving operation can not be performed. Replacement of the heart valve of these atriovetricular valve substitutes ensures their high throughput and good blocking function while preserving the annulopapillary continuity of the ventricles, which ensures a high functional result.

Prosthesis of the mitral valve with a homograft was one of the first operations in the course of the development of valvular heart surgery. Experimental studies in the early 60s of the 20th century on animal models had inspiring results demonstrating the rapid integration of homografts, the valves and chords of which remained intact one year after implantation. Nevertheless, the first attempts to prosthetic mitral valve mitral homograft in the clinical situation were associated with the development of early valve dysfunction due to a misunderstanding of the function of the valve apparatus and because of the difficulty of fixing the papillary muscles. The progress achieved over the past 20 years in evaluating the mitral valve through echocardiography has significantly increased the knowledge base of valvular pathophysiology. The experience gained in reconstructive surgery of the mitral valve allowed surgeons to master operational techniques on the valve.

The essence of the operation of implantation of a frameless substitute for atrioventricular valves is reduced to suturing the tips of the papillary muscles of the allo- or xenograft to the patient's papillary muscles, and then fixing the fibrous ring of the graft to the recipient's fibrous ring. The operation consists of several stages. After excision of the patient's pathologically altered valve, the anatomy of his papillary muscles is evaluated, the caliber of the atrioventricular opening and the distance between the fibrous triangles are measured. Then, the size of the graft is selected, guided by the measurements made, and the implant on the holder is placed in the ventricle cavity, trying on its relative to the papillary muscles, the fibrous ring of the patient, and on the coincidence of the sizes between the fibrous triangles. Calculate the level of suturing the papillary muscles. The tops of the implant are fixed to the papillary muscles with P-shaped seams on the pads carried through the bases of the papillary muscles.

After tying the U-shaped seams, the second (upper) row of seams is performed by continuous or single seams. Initially, the seams, provisional in the field of fibrous triangles, are passed through the marked sections of the fibrous ring of the graft. After restoration of cardiac activity, an intraoperative transesophageal echocardiographic evaluation of the graft closure function is mandatory.

Replacement of the heart valve of cryoprotected mitral homografts according to Asar et al. (1996). The complex of the mitral apparatus is excised in patients undergoing cardiac transplantation at the sites of attachment of papillary muscles to the walls of the ventricle and myocardium surrounding the fibrous ring of the mitral valve. This manipulation is performed under operating conditions. Cryopreservation is carried out for 18 hours, during which homografts are in the tissue bank. A 5% preservative solution of dimethyl sulfoxide is used without the addition of antibiotics. Conservation is carried out with a gradual decrease in temperature to -150 ° C. Morphological characteristics of the papillary muscles and the distribution of chords are recorded for each homograft and recorded in the identification map. The recorded characteristics of the valve are the height and area of the anterior mitral valve, measured by the obturator for annuloplasty, and the distance between the apex of the papillary muscle and the fibrous ring of the mitral valve. Papillary muscles are classified according to their morphological features and are divided into 4 types. Protection of the myocardium is carried out through cold cardioplegia through the root of the aorta. Access to the left atrium is performed by a classical parallel incision through the interatrial groove. The mitral valve is then inspected to assess the pathological process and to make a final decision on the type of surgery. If there is an isolated lesion affecting less than half the valve (calcification or valve abscess), only a part of the homograft is implanted, provided that the rest of the valve is normal. On the other hand, in the presence of extensive damage involving the entire pathological process of the valve, the mitral valve is fully prosthetic with a homograft. When implanting a mitral homograft, the pathologically altered valve tissue is first excised along with the corresponding chords, the integrity of the papillary muscles is carefully preserved. Their mobilization is carried out by separating the muscular layers attached to the wall of the left ventricle. The replacement of the heart valve of homograft begins with the fixation of the papillary muscles. Exposure of the papillary muscle of the recipient is clearly visible by its traction over the suture-holder. Each papillary muscle of the homograft is fixed to the cut between the native papillary muscle and the wall of the left ventricle. The head of the homograft's papillary muscle, supporting the commissure, is used as a control point and placed on the corresponding site of the native papillary muscle. This site is easily determined, since commissural chords invariably originate from the apex of the papillary muscle. Typically, the papillary muscle of the homograft is sutured side-by-side to the papillary muscle of the recipient to be placed at a lower level. To stitch the papillary muscles a double row of mattress sutures is used, protected by numerous interrupted sutures. The annuloplastic ring of the Carpentier is attached to the fibrous ring of the recipient. The size of the annuloplastic ring is selected based on the size of the anterior flap of the homograft measured by the obturator. The homograft fabric is then sewn to the Carpentier ring by means of a 5-0 polypropylene suture. Different parts of the valve are sewn in the following order, posterior-medial commissure, anterior valve, anterolateral commissure, posterior valve. Particular attention is paid to the location of the commissure. In the areas of the anterior valve and commissure, the seams are applied without tension. In cases of excess or insufficient tissue of the folds of the homograft with respect to the annuloplastic ring, the suture line is corrected to achieve balance during suturing the posterior mitral valve. After implantation of homograft, the result is estimated by infusion of physiological solution under pressure into the ventricle (hydraulic sample). C Asar et al (1996) conducted a series of implantations of cryoprotected mitral homografts to 43 patients on the acquired pathology of the mitral valve, as described above, with satisfactory long-term results (14 months later) .

[1], [2], [3], [4]

Heart valve replacement: immediate and long-term results

Hospital or the nearest lethality within 30 days after the operation of an isolated prosthetics of the mitral or aortic valve, including combined aortocoronary shunting (ASCH), was 10-20% 15-20 years ago. In recent years, perioperative mortality has significantly decreased to 3-8% and is due to the presence of severe chronic cardiac and pulmonary insufficiency, severe chronic lung diseases, multiple organ dysfunction, diabetes and postoperative development of patients with various complications: hemorrhage, acute purulent infection, infarction myocardium, acute disorders of cerebral circulation, etc. Decrease in lethality in the last decade is associated with an improvement in the surgical technique of implantation of valves, the method of performing artificial circulation, the protection of the myocardium through the introduction of blood antegrade and retrograde cardioplegia, anesthesia and resuscitation, as well as the use of more advanced models of artificial heart valves and bioprostheses. Hospital mortality remains higher in emergency and urgent operations performed according to vital indications, with re-operations (repeated operations) and combined surgical interventions. It was noted that most complications and deaths occur in the first 3-5 years after the operation, then stabilization of survival occurs.

The criterion of the functional efficiency of the implanted valve in maintaining homeostatic stability is the actuarial survival rate of patients - the absence of lethality from valve-dependent complications. In 90% of patients who underwent prosthetic repair of the mitral or aortic valve, the signs of chronic heart failure are largely eliminated or reduced, making them pass to the I-II functional class (according to the NYHA classification). Only a small group of patients remain in III or IV FC, which is usually associated with low contractility of the myocardium before surgery, high initial pulmonary hypertension and concomitant pathology. Survival and quality of life indicators are better in patients with artificial heart valves in the aortic position than in the mitral position. However, survival may be significantly impaired with an increase in the pressure gradient on the artificial valve, the increase in chronic heart failure and the duration of postoperative follow-up.

Essential effect on the state of homeostasis in the body, survival and quality of life of operated patients have hemodynamic parameters of the artificial heart valve As can be seen from Table. 6.2, all artificial heart valves resist blood flow, especially when loaded: ball valves have a greater pressure drop than rotary discs, and bivalves have the lowest resistance. In clinical practice, a detailed study of the hemodynamic characteristics of artificial heart valves seems complex. Therefore, the effectiveness of valves is judged on the peak and average pressure difference on the valve, detected both at rest and under the load of transthoracic and transesophageal opplerehokardiografiey (Doppler echocardiography) whose values have a good correlation with those obtained during catheterization of the heart cavities.

Pressure and / or volume overload caused by aortic valve pathology leads to increased pressure in the left ventricular cavity and its compensatory hypertrophy Severe aortic insufficiency causes an overload of left ventricular volume with an increase in its end-diastolic volume and the development of eccentric left ventricular myocardial hypertrophy. In severe aortic stenosis, the concentric hypertrophy of the myocardium of the left ventricle occurs without an increase in the end-diastolic volume until the late stage of the process, thus increasing the ratio of the wall thickness and the radius of the ventricular cavity. Both pathological processes lead to an increase in left ventricular myocardial mass. A positive effect after aortic valve replacement is to reduce the volume and pressure of the left ventricle, which contributes to the remodeling and regression of its mass in the near and distant observation periods.

Despite the fact that the clinical and prognostic value of reducing the mass of the left ventricular myocardium is not yet fully understood, this concept is widely used as

A measure of the effectiveness of aortic valve replacement. It can be assumed that the degree of decrease in the mass of the myocardium of the left ventricle should be associated with the clinical outcome of the operation, which, especially in young patients, is of fundamental importance for their physical adaptation and subsequent employment in occupations related to physical stress.

Studies performed in patients after aortic valve replacement showed that the risk of developing cardiac complications was significantly lower in those patients who had achieved a reduction in the mass of the left ventricular myocardium. In this case, the replacement of the heart valve with the optimal prosthesis size for isolated aortic stenosis left ventricular mass was significantly reduced and in a number of patients it reached normal values within the first 18 months. Regression of the ventricle mass lasts up to 5 years after the operation. The situation when the inadequate hemodynamic characteristics of the prosthesis does not lead to a significant decrease in the mass of the left ventricular myocardium, which determines the unsatisfactory result of the operation, is regarded by some authors as a prosthetic-patient incompatibility.

The decrease in patient survival in the long term after the operation, in addition to risk factors, is also associated with the negative aspects of the ball artificial heart valves of large dimensions and mass, increased pressure gradient, inertia of the locking element, leading to a reduction in shock release and increased thrombus formation. However, according to some authors, the use of spherical artificial heart valves is justified in the mitral position with large volumes of the left ventricle expressed by calcification, or in the aortic - with aortic root diameter> 30 mm, due to their durability of mechanical reliability, satisfactory hemodynamic qualities over 30 years of work in the body. Therefore, spherical artificial heart valves are too early to write off from cardiac surgery.

With the rotary disc heart valves Lix-2 and Emix (Mix), Bjork-Shiley, Sorm, Omniscience, Omnicarbon, Ullehei-Kaster, Medtromc-Hall in the aortic position by 5-25th year, the actuarial survival rate of patients is slightly higher, than with ball valves, ranging from 89% to 44%, and in the mitral range from 87% to 42%. Rotational disc heart valves, especially Medtromc-Hall, which has the greatest opening angle and competes in hemodynamic efficiency with bivalve mechanical heart valves , are known for their advantages over ball clays Anami is good hemocompatibility, reduce thrombosis artificial heart valves and thromboembolic complications, smaller losses of energy and flow resistance, speed, small size and weight, better flow structure.

Replacing the heart valves of the rotary disc valves, in comparison with the ball valves, morphofunctional parameters of the heart are significantly improved. Their hemodynamic advantage favorably affects the course of the immediate and distant postoperative period, especially in patients with atrial fibrillation, and acute heart failure and "low cardiac output syndrome" become two times less frequent than with ball valves.

A noticeable hemodynamic advantage was noted in patients with implantation of bivalve artificial heart valves Medinzh-2; Carbonix-1; St. Jude Medical; Carbomedics; Sonn Bicarbon; ATS in both mitral and aortic positions with respect to rotary disc and, especially, spherical pressure gradient on the valve, effective valve area, valve performance, reduction in heart chamber volumes, myocardial mass, as well as actuarial survival and stability of good results from 93% to 52% to 5-15 years in the mitral position and from 96% to 61% in the aortic.

The joint document STS / AATS of the Society of Thoracic Surgeons of the United States provides definitions of specific non-fatal valve-dependent complications of non-infectious and infectious origin, leading to a decrease in actuarial survival, quality of life and disability. Non-infectious valve-dependent complications include structural dysfunction of the valve - any changes in the function of the implanted valve due to its wear, breakage, wedging of the valves or breakage of the suture line, leading to stenosis or regurgitation. Non-structural valve dysfunction includes any valve dysfunction that is not related to its failure: a discrepancy between the size of the valve and surrounding structures, paraplanic fistula leading to stenosis or regurgitation.

Actuarial and linear indicators of structural dysfunction of mechanical valves are 90-95% and 0-0.3% patient-years, respectively. Long-term follow-up of patients with ball mechanical valves MCH, ACH, Starr-Edwards, and also rotary discs Lix-2, Mix, Emix, Medtronic-Hall and bivalve Meding-2, Carbonics-1, St Jude Medical, Carbomedics, etc. Showed that these valves are extremely resistant to structural breakdowns. A number of non-currently used mechanical prostheses, such as Bjork-Shiley Convexo-Concave, had a fragility of the limiter and were excluded from clinical practice. Unlike mechanical valves, structural degeneration of bioprostheses, on the contrary, is the most common non-lethal valve-dependent complication. Thus, a long-term observation of the second-generation framework bioprostheses used, including the pig Medtronic Hankock II and pericardial Carpenter-Edwards, showed that in the aortic position of more than 90% of the bioprosthesis, structural degeneration does not develop for 12 years, while in the mitral position, it occurs much earlier due to more pronounced systolic loads on the valves of the prosthesis.

The formation of paraplanar fistula at an early or late time after surgery can be facilitated by the development of prosthetic endocarditis or massive calcification of the fibrous ring, as well as technical errors during implantation of the valve.

Hemodynamically significant para-valentine fistulas usually cause refractory hemolytic anemia, in contrast to the clinically insignificant degree of chronic intravascular hemolysis that occurs after implantation of virtually all mechanical, especially ball and rotary-disc valves.

Technical errors in the form of too large gaps between the seams contribute to the formation of areas of loss without tight contact with the fibrous ring of the valve, which eventually leads to the formation of a fistula. If the paraplanar fistula is hemodynamically significant and causes hemolysis accompanied by anemia and requiring blood transfusions, the fistula or valve .

As a result of the improvement of surgical methods, the occurrence of paraclavanic fistulas has recently decreased and, according to the linear indices, ranges from 0% to 1.5% of patient-years for both mechanical valves and for bioprostheses. Some authors noted the growth of para-valentine fistulas after implantation of mechanical bivalves, as compared to bioprostheses, considering that this is due to the use of an eversion suture and a narrower sutured cuff.

Despite the improvement of surgical techniques, postoperative care and antibiotic prophylaxis, prosthetic endocarditis remains one of the unresolved problems of cardiac surgery and meets up to 3% of complications after prosthetic heart valves. Despite the fact that the materials from which mechanical artificial heart valves are manufactured have thrombus-resistant properties, the source of infection may be the sutures fixing the prosthesis to

The tissues of the heart, where non-bacterial thrombotic endocardial

Damage that can be infected during transient bacteremia. When the prosthesis is damaged in the aortic position, its insufficiency often occurs (67%), and if the mitral valve prosthesis is affected, its obstruction (71%) occurs. Abscesses of the fibrous ring are found in 55% of cases of prosthetic endocarditis. Infectious endocarditis of the valve bioprosthesis causes not only the destruction of the valves, but also abscesses of the sewing ring, which develop more often during the first year after the operation than at later times - 27%).

Depending on the development period, prosthetic endocarditis is divided into early (within 60 days after the operation) and late (more than 60 days). Early prosthetic endocarditis occurs in 35-37% of cases and is usually a consequence of bacterial contamination of the valve, either during implantation intraoperatively or by hematogenous way in the postoperative period from a wound or venous catheter with intravenous infusions. Epidermal and golden staphylococcus prevail in this period (28.1-33% and 17-18.8% of cases, respectively), enterococcus - 6.3%, green streptococcus - 3.1%, gram-negative bacteria and fungal flora. Cases of infective endocarditis of viral etiology are described, in spite of the fact that in most cases late prosthetic endocarditis (the occurrence of 60-63%) is associated with noncardial septicemia.

According to D. Horstkotte et al. (1995), most often late prosthetic endocarditis occurs as a complication after dental manipulation (20.3%), urological manipulation and urosepsis (13.9%), intensive therapy with permanent venous catheters (7.4%), pneumonia and bronchitis (6.5%), manipulation of the respiratory tract (5.6%), fibroscopic examination of the digestive tract (4.6%), trauma, wound infection (4.6%), abdominal surgery (3.7%), labor ( 0.9%). In some cases, it can be caused by nosocomial infection with malovirulent pathogens oral epidermal staphylococcus.

Actuarial and linear indicators of the incidence of prosthetic endocarditis in the aortic position are 97-85% and 0.6-0.9% of patient-years, respectively, in the aortic position are slightly higher than in the mitral position. Five-year freedom from bioprosthetic endocarditis, according to most major studies, is more than 97%. The risk of prosthetic endocarditis for mechanical valves is slightly higher than for bioprostheses.

Prosthetic endocarditis of frameless bioprostheses and allografts is less common, so these valves can be more useful when replacing a mechanical prosthesis during a reoperation for prosthetic endocarditis. Intravenous antibacterial therapy is administered under the control of the sensitivity of the blood culture and should be started as soon as possible. Experience shows that when infected with malovirulent microorganisms (more often streptococci), most patients with prosthetic endocarditis can be cured conservatively. However, this therapy, especially when it comes to infection with highly virulent flora (staphylococcus, fungal infection), should be supplemented by the introduction of antiseptics, and the immune status of the organism is corrected. Prosthetic endocarditis often requires urgent and sometimes urgent surgery.

The most dangerous complication in the long-term follow-up in patients who underwent reimplantation of an artificial heart valve is its reinfection. The probability of re-infection of the prosthesis after a second operation depends on the reactivity of the organism and the surgeon's ability to completely eliminate all foci of infection during the primary operation. The results of treatment of prosthetic endocarditis need to be improved The frequency of development of paraplanal infections in patients with prosthetic endocarditis can reach 40%. Mortality with an early prosthetic endocarditis is 30-80%, and in the late-20-40%.

Valvular complications include chronic intravascular hemolysis caused by direct mechanical damage to blood cells by a working artificial heart valve, a distorted structure of the blood flow during flow around the valve, turbulence, septic currents, rarefactions, increased physical exertion, any chronic infection, pannus proliferation, structural degeneration bioprostheses, thrombosis of the artificial heart valve, violation of the tissue covering and endothelial lining of the saddle and artificially valve, renal and hepatic insufficiency al. In such situations, the process of changing homeostasis takes the form of a negative spiral flow with the rapid development of irreversible changes that lead to time-vitiyu syndrome, chronic disseminated intravascular coagulation and multiple organ failure, which cause thrombotic complications. The development of chronic intravascular hemolysis is affected by autoimmune mechanisms, excessive appearance of active forms of oxygen, and activation of lipid peroxidation during hypoxia. Hemoglobin and iron ions released by chronic intravascular hemolysis are themselves powerful activators of lipid peroxidation. The level of chronic intravascular hemolysis does not change from the period of implantation of the artificial heart valve with its satisfactory function, does not affect the level of chronic intravascular hemolysis atrial fibrillation and the degree of chronic heart failure. With the use of normally functioning modern mechanical or skeletal biological prostheses, hemolysis is rare. Chronic intravascular hemolysis in patients with mechanical heart valves occurs with a frequency of actuarial and linear measures of 99.7-99.8% and 0.06-0.52% of patient-years, respectively. Such a significant spread of the frequency of chronic intravascular hemolysis does not allow to objectively assess the advantages of a particular design of an artificial heart valve or bioprosthesis. In addition, at present there are no unified accurate biochemical tests for assessing the severity of hemolysis.

Chronic intravascular hemolysis, even at a clinically insignificant level, leads to a violation of blood rheology, progressive hemolytic anemia, hemostasis disorder and thrombus formation due to the release of thromboplastin-like material from destroyed erythrocytes, liver pigmentation function, hemosiderosis of kidneys, renal failure, iron deficiency anemia, and contributes to the development of septic endocarditis.

Treatment of chronic intravascular hemolysis in patients with artificial heart valves is carried out individually, depending on its degree, dynamics of development and the cause caused. In the case of decompensated chronic intravascular hemolysis, a restriction of physical activity, maintenance of erythropoiesis and replacement of iron losses (iron preparations, folic acid, etc.) are shown; To stabilize erythrocyte membranes, tocopherol, steroid hormones are prescribed in patients with positive autoimmune tests, with severe anemia - blood transfusion erythropoietin under the control of hemoglobin, haptoglobin, lactate dehydrogenase.

Thrombemboli and thrombosis of valves are the most common valve-dependent complications of the postoperative period in patients with mechanical and biological mitral valve prostheses, leading to a deterioration in the quality of life and disability. Most often they occur in patients with mechanical valves. More than 50% of patients after prosthetics of the mitral valve with chronic atrial fibrillation and other risk factors (low ejection fraction, history of thromboembolic complications, large size of the left atrium, thrombus in its cavity, etc.) are prone to thromboembolic complications, despite adequate anticoagulant therapy, and also increased probability of thrombosis of mechanical valves in cases of changes in the protocol of anticoagulant therapy. Thromboembolism is relatively rare in patients after prosthetics of the mitral valve with a small volume of the left atrium, sinus rhythm and normal cardiac output. In addition, patients with out-of-date types of valvular prostheses receiving more intensive anticoagulant therapy may develop severe hypocoagulation bleeding.

Among the numerous etiologic risk factors for thrombotic complications, the main ones are: inadequacy of anticoagulant therapy, activity of rheumatic process and infective endocarditis, especially prosthetic endocarditis with large vegetation; slowing and stasis of blood flow, associated with low minute volume of blood circulation, hypovolemia, atrial fibrillation, violation of myocardial contractility. Coagulopathy of consumption and the syndrome of disseminated intravascular coagulation, pulmonary hypertension can lead to an increase in fibrinogen, an imbalance of thromboxane and prostacyclin, endothelin-1, promote endothelial dysfunction, and thrombosis. In addition, para-valvular fistula and regurgitation on the artificial heart valve lead to an even more distortion of the blood flow structure with the development of increased tearing currents, shear stresses, turbulence, cavitation, endothelial dysfunction, chronic intravascular hemolysis and thrombus formation.

A rare and extremely dangerous complication is thrombosis of the valve prosthesis, whose risk does not exceed 0.2% of patient-years, it is more common in patients with mechanical valves. The frequency of actuarial and linear indices of thrombosis of mechanical artificial heart valves ranged from 97% to 100% and from 0% to 1.1% of patient-years, and in the mitral position, these values are higher than in the aortic valve. Such a significant spread of indices of thrombosis of artificial heart valves and thromboembolic complications can be explained by various initial risk factors and the level of anticoagulant therapy in patients. According to the combined data of a multicenter randomized study of foreign cardiac surgery centers, all cases of thrombosis of artificial valves Carbomedics were registered in patients with a violation of the anticoagulation regimen below the recommended level for MHO (INR) (2.5-3.5) and prothrombin time (1.5), in some patients, anticoagulant therapy was interrupted. In this regard, the actuarial valve thrombosis rate in patients with artificial heart valves Carbomedics was 97% by the fifth year, linear - 0.64% patient-years in the mitral position, and in the aortic position - thrombosis of artificial heart valves was not noted. For 4000 implantations of artificial heart valves, Lix-2 and Emix thrombosis was 1%.