Mechanical prostheses of valves of heart

Description:

Prosthetics of valves of heart - surgery of replacement with a prosthesis of one or several valves of heart which function it is irreversible is broken.

Need of replacement of the struck valve with a prosthesis arises at patients with the acquired or inborn changes of structure and function of the valve device of heart which are not subject to plastic correction. Most often carry out prosthetics of mitral and (or) aortal valves. Thanks to modern opportunities of cordial surgery operation of prosthetics of valves of heart became usual for the specialized cardiac centers. At the same time the leading value in achievement of the good long-term results at patients which are carriers of valve prostheses gets the qualified control and treatment of these patients from the doctor of policlinic at the place of residence.

At relative safety of the valve device (lack of rough fibrous changes and calcification of shutters) surgeons aim to execute klapanosokhranyayushchy operation. Prosthetics of valves of heart is carried out with use of mechanical (artificial) or biological (fabric) prostheses.

Mechanical valves of heart have the locking element of valve or petal type made of artificial material (silicone, compounds of graphite) placed in a metal framework. Also spherical valves have a clinical use, but at a number of patients use of spherical valves is impossible because of rather big sizes of a framework of a prosthesis. In these situations the low-profile disk or folding prostheses having small dimensions and weight, a smaller inertance of a locking element and providing close to central a blood flow are preferable. Common fault of mechanical prostheses of valves of heart is need for the patient of lifelong reception of anticoagulants and monthly control of indicators of coagulant system of blood because of danger of tromboembolic episodes.

At patients with high risk of tromboembolic episodes (fibrinferments of the left auricle, a thromboembolism in the anamnesis, the considerable sizes of cardial cavities and a ciliary arrhythmia, tendency to the accelerated thrombogenesis), at contraindications to performing anticoagulating therapy (a peptic ulcer of a stomach and duodenum, a stage IIB idiopathic hypertensia, an urolithiasis, metrorrhagias), and also at elderly people it is more preferable to use biological prostheses of valves of heart. These prostheses have the natural three-leaved locking element of the biological nature (the ksenaortalny valve, ксеноклапан from a pericardium, аллоклапан from a firm meninx, preserved in solution of a glutaraldegid) fixed on a polymeric or metal basic framework. Hemodynamic properties, the small sizes and weight, lack of hemolysis are characteristic of biological prostheses of valves of heart close to natural. However during the remote periods the biodegeneration of valves in the form of calcification and a rupture of shutters is noted. The main advantage of biological prostheses in front of mechanical valves is absence or small risk of thrombosis and thromboembolisms.

Operations on prosthetics of valves of heart carry out on the stopped heart in the conditions of artificial circulation and a cold cardioplegia.
When determining medical tactics (surgical or therapeutic) at the patient with heart disease it is necessary to estimate expressiveness of valve dysfunction and a condition of sokratitelny function of a myocardium that in most cases it is possible to make on the basis of results of noninvasive methods of an issledovaniyaniye - an electrocardiography, a phonocardiography, a X-ray analysis, an echocardiography.

As the indication to prosthetics serve the rough changes of the valve device of heart with the expressed calcification and fibrosis of shutters leading to blood circulation disturbance. At a bacterial septic endocarditis indications to P. to. pages are the progressing heart failure, inefficiency of antibacterial therapy, embolic complications, echocardiographic signs of existence of vegetations and destruction of valves.

Contraindications to operation are connected by the general serious condition of the patient and substantially depend on damages of the lungs, a liver and kidneys which developed as a result of congestive heart failure and the accompanying pathology of these bodies. Artificial circulation at heart failure quite often leads to development of irreversible respiratory and hepatonephric insufficiency. Therefore timeliness of the direction of patients with valve defects in a cardiac hospital gains paramount value in achievement of the good immediate and long-term results of prosthetics. Prosthetics of valves of heart is contraindicated also in the presence in an organism of the center of an infection of any localization (antritis, tonsillitis, cholecystitis, pyelonephritis, an endometritis, caries of teeth, etc.) because of danger of development of infectious endocarditises after operation. Therefore at selection of patients for surgical treatment of heart disease it is necessary to conduct comprehensive examination for the purpose of identification of the centers of an infection and sanitation of an oral cavity, treatment of all chronic diseases. Hospitalization has to be carried out to a cardiac hospital not earlier than in a month after extraction of tooth and in three months to any band operation. In the first 6 months after P. to. pages all patients need restriction of an exercise stress and observance of the water-salt mode with reduction of the use of table salt and liquid and sufficient content of salts of potassium and magnesium in food. During this period use of small doses of cardiac glycosides, kaliysberegayushchy drugs, anabolic means is shown. More careful control of the water-salt mode, additional purpose of vazodilatator, gepatoprotektor should be recommended to patients with a stage IIB circulatory unefficiency.

Patients with rheumatic defects and various degree of activity of rheumatism have to receive antiinflammatory therapy taking into account a degree of activity of rheumatic process (according to a clinical current and a histologic research of the valve removed on operation). Duration of antirheumatic therapy is defined at dynamic observation of patients and conditions of therapeutic department. In the absence of dysbacteriosis and an allergy to penicillin purpose of Bicillinum all the year round is shown to the patients having the chronic centers of a streptococcal infection in a nasopharynx. The most terrible complication of P. to. the page is a thrombembolia which developing is promoted by a ciliary arrhythmia, inadequate anticoagulating therapy or its sudden cancellation, an aggravation of rheumatic process, a late septic endocarditis, valve prosthesis dysfunction.

Prevention of a thromboembolism demands vital anticoagulating therapy from patients with artificial valves of heart. At the uncomplicated course of operation since second day of the postoperative period to patients appoint heparin of 4-6 times a day. The single dose of drug is selected individually under control of a tromboelastogramma for the purpose of achievement of the moderate hypocoagulation interfering a thrombogenesis. From 5th days after operation appoint indirect anticoagulants against the background of a gradual dose decline of heparin which is cancelled at achievement of necessary level of a prothrombin ratio (PTI), and now more exact is the indicator of the international normalized relation (INR). Further the patient receives indirect anticoagulants constantly, with weekly control of PTI (MNO). However it is necessary to remember that the daily dose of drug can vary depending on contents in vitamin K food that demands more careful control of PTI (MNO) in the spring (a tendency to hypocoagulation) and at the end of summer and in the fall (a hypercoagulation tendency). It is also necessary to consider strengthening of effect of indirect anticoagulants at use of non-steroidal anti-inflammatory drugs, trental and a komplamin. On the other hand, it is necessary to remember weakening of their action at co-administration of glucocorticoid hormones, diuretic, contraceptives, Essentiale. Additional purpose of one of the listed drugs demands more frequent control of PTI (MNO) with the subsequent dose adjustment of indirect anticoagulants. At emergence of symptoms of hypocoagulation (the hamaturia, bleeding of gums or a mucous membrane of a nose) needs to reduce a drug dose without sharp cancellation and to investigate PTI (MNO) in dynamics. Uncontrollable hypocoagulation, symptoms of intracavitary bleeding, a melena are the indication for urgent hospitalization in a hospital at the place of residence. It is also necessary to remember that sudden decrease in tolerance to indirect anticoagulants with the advent of a hemorrhagic syndrome can be clinical display of the developing hepatitis.

Special control is demanded by anticoagulating therapy when carrying out various emergency and planned surgical interventions from patients with artificial valves of heart. When carrying out an immediate surgery it is necessary to stop immediately reception of indirect anticoagulants, and since 2 days of the postoperative period to begin administration of heparin subcutaneously at least 4 times a day under control of a tromboelastogramma. At the uncomplicated postoperative period from 5th days it is necessary to begin transfer of the patient into indirect anticoagulants.
By training the patient with the artificial valve of heart to planned operation it is necessary in 3 days prior to its performance to cancel indirect anticoagulants and to appoint 2,5-5 thousand units of heparin 4 times a day. The last injection of heparin should be done the night before for 12 h before operation. At the smooth postoperative period since 2 days reappoint heparin, and from 5th days begin transfer into indirect anticoagulants. In case of carrying out out-patient operation and at impossibility of control for tromboelastogrammy in 1 day prior to operation cancel indirect anticoagulants and since 2 days reappoint them.

Terrible postoperative complication both in early, and during the remote period after operation is the infectious prosthetic endocarditis. At its emergence of patients it is necessary to hospitalize immediately in a cardiac hospital.

Prevention of an infectious endocarditis after P. to page represents one of the most urgent problems of a modern heart surgery. Now the greatest attention is paid to elimination of sources of bacteremia by sanitation of any centers of an infection in the patient's organism. Purpose of antibacterial drugs with the medical purpose at the acute purulent and inflammatory diseases which are followed by passing bacteremia is important; preventive prescription of antibiotics for the bacteremia connected with operative measures (including extraction of tooth) and manipulations (cardiac catheterization, a tsistoskopiya). Preventive administration of antibacterial drugs is begun for an hour before operation or manipulation and continued no more than 3 days.

The choice of antibacterial drugs for treatment of inflammatory and purulent diseases has to be based on individual sensitivity of the allocated microorganism to the available means. At impossibility to carry out identification of a contagium appoint the antibiotics of a broad spectrum of activity or drugs suppressing the most often allocated species of microorganisms taking into account their specific sensitivity.

At preventive prescription of antibiotics for tool manipulation or operation the choice of drug depends also on specific sensitivity to it the most often found contagiums at this localization of possible inflammatory process.

The long fever arising at the patient with the artificial valve of heart has to serve as a signal to intensive antibacterial care by drugs of a broad spectrum of activity before which carry out repeated (not less than 3 times a day) blood crops. At the same time specify possible localization of the extracardiac center of an infection and carry out its sanitation against the background of the continuing intensive antibacterial care. Allocation of a hemoculture is finished with definition of sensitivity of microorganisms to antibiotics for selection of adequate antibacterial therapy. Long unmotivated fever at the patient with the artificial valve of heart is the indication for treatment in a hospital with careful bacteriological inspection in connection with suspicion of an infectious endocarditis.

One of rare, but typical complications after prosthetics of the valve of heart is development of a paraprosthetic fistula. At the same time there are pathological noise (diastolic on aortal and systolic on a mitral valve prosthesis) and depending on blood regurgitation degree disturbance of a hemodynamics. If dumping of blood through a paraprosthetic fistula leads to permanent disturbances of the central and peripheric circulation, it is necessary to raise a question of repeated operation - sewing up of a fistula or reprotezirovaniya. Are the most frequent origins of paraprosthetic fistulas rough calcification when replacing the valve, and also the activity of rheumatic process or an infectious endocarditis leading to eruption of the seams fixing a valve prosthesis.

At a favorable current of the postoperative period the first and obligatory inspection by the cardiosurgeon has to be performed in 6 months. At a clear positive take (reduction of the sizes of heart, the compensated blood circulation, (lack of signs of the current rheumatic process and an infectious endocarditis) it is necessary to resolve an issue of expansion of level of exercise stresses, and at an opportunity of recovery of a sinoatrial rate at patients with a ciliary arrhythmia at defects of the mitral valve.

Approximately at 1/3 pregnant women with artificial mechanical valves of heart trombogemorragichesky complications, misbirths, and also embryopathies are observed. Biological valves of heart in this respect are the least dangerous.
More than 30 years' experience of prosthetics of valves of heart demonstrates that duration and quality of life operated considerably exceeds those at patients without operation with the natural course of a disease. Most of the operated patients are capable to have a family and to be returned to the professional activity.