RU2845237C1 - Method for open implantation of a self-expanding aortic valve prosthesis in experiment - Google Patents

Abstract

FIELD: medical science.

SUBSTANCE: invention refers to medicine, namely cardiosurgery. Aortic valve is approached through transverse aortotomy 0.5 cm above a sinotubular junction with the incision extended towards a non-coronary sinus. Native cusps of the aortic valve are removed. Nitinol support frame is implanted into the intraannular position by means of U-sutures within the commissures of the native aortic valve. Mattress suture is used to suture the posterolateral semi-circles of the aortic approach with placing inside the implanted nitinol support frame compressed and fixed in the upper part of the frame of the aortic valve prosthesis. Warming is carried out by irrigation with warm 36 °C normal saline for the purpose of self-fixation of the lower "skirt" of the frame. Ligature fixing the crown of the prosthetic valve is removed, and the aortic opening is closed.

EFFECT: method allows to strengthen the left ventricular output and to isolate the boundaries of the permissible extension of the aortic valve prosthesis due to the implantation of a nitonol frame, which helps to prevent the development of a number of life-threatening complications: prosthesis migration, coronary circulation disorder, atrioventricular block, aorto-left ventricular fistula and mitral regurgitation.

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Description

The invention relates to medicine, namely to cardiac surgery, and can be used for the purpose of conducting preclinical tests of new models of self-expanding aortic valve prostheses for transcatheter implantation.

State of the art.

Today, aortic valve stenosis is considered an important medical and social problem almost all over the world (Otto C. M. et al. 2017 ACC expert consensus decision pathway for transcatheter aortic valve replacement in the management of adults with aortic stenosis: a report of the American College of Cardiology Task Force on Clinical Expert Consensus Documents // Journal of the American College of Cardiology. - 2017. - Vol. 69. - No. 10. - Pp. 1313-1346.). Thus, according to statistics, in the structure of diseases of the circulatory system, aortic valve stenosis ranks third after arterial hypertension and coronary heart disease (Kranin D.L. et al. Contrast-induced nephropathy after transcatheter implantation of the aortic valve // Almanac of Clinical Medicine. - 2017. - Vol. 45. - No. 3. - Pp. 242-246.). The relevance of this disease is especially great in the older age group - in developed countries, aortic valve stenosis is the most common heart defect (Cribier A. et al. Percutaneous transcatheter implantation of an aortic valve prosthesis for calcific aortic stenosis: first human case description // Circulation. - 2002. - Vol. 106. - No. 24. - Pp. 3006-3008.).

The minimally invasive nature of the transcatheter implantation of aortic valve prostheses (TAIP) technology allows to significantly reduce the risk of complications and the duration of hospitalization compared to the traditional technique of open prosthetics, which, in turn, helps to reduce the costs of the intervention (Kretov E.I. et al. The first experience of transcatheter implantation of a prototype of a new self-expanding aortic valve prosthesis in an experiment // Pathology of blood circulation and cardiac surgery. - 2016. - Vol. 20. - No. 4. - P. 83-87.). According to the recommendations, TAVI is currently indicated for patients with severe, symptomatic, calcified tricuspid aortic valve stenosis, suitable anatomy, predicted life expectancy of more than 12 months, patients with excessive surgical risk, previous radiation therapy, "porcelain aorta", severe concomitant pathology (ESC/EACTS 2017 Guidelines for the Treatment of Valvular Heart Disease // Russian Journal of Cardiology. - 2018. - Vol. 23. - No. 7. - P. 103-155.).

The surgical technique of transcatheter implantation of aortic valve prostheses depends on the model of the implanted valve. However, in general, it has similar stages. Today, the most common are transfemoral and transapical approaches. The advantage of transfemoral access is the possibility of performing this intervention under local anesthesia. The transapical method is more often used in patients with severe atherosclerosis of the lower extremity vessels, as well as calcification and tortuosity of the aorta. After standard transseptal catheterization of the left heart, a straight 0.035-inch guidewire is passed through the stenotic aortic valve using a balloon flotation catheter. After insertion of the balloon catheter into the descending aorta, the guidewire is replaced with a rigid guidewire 260 cm long. After dilatation of the interatrial septum with a 10 mm diameter balloon catheter and compression of the prosthesis using a mechanical crimping device on a 3 cm long and 23 mm diameter balloon catheter, it is placed in the projection of the stenotic aortic valve. After this, the balloon is maximally inflated, quickly deflated and removed (Cribier A. et al. Percutaneous transcatheter implantation of an aortic valve prosthesis for calcific aortic stenosis: first human case description // Circulation. - 2002. - Vol. 106. - No. 24. - P. 3006-300

The difficulty of experimental implantation of new models of self-expanding aortic valve prostheses is mainly determined by the anatomical features of the aortic root of healthy animals. In the case of using the traditional technique of transcatheter implantation of a self-expanding aortic valve prosthesis, the number of post-implantation complications in the experiment remains extremely high. According to Dewey et al., the frequency of migration of prostheses after successful positioning in the aortic position of pigs is 31%, the frequency of development of para-aortic fistulas is 77.8% (Dewey T.M. et al. Transapical aortic valve implantation: an animal feasibility study // The annals of thoracic surgery. - 2006. - Vol. 82. - No. 1. - P. 110-116.).

The main factor determining the high risk of failure in experimental transcatheter implantation of aortic valve prostheses is the lack of sufficient native rigidity of the aortic root in healthy animals and a short landing zone, which leads to migration of the valve prosthesis, even in the case of optimal positioning (Kappetein A. P. et al. Transapical implantation of a self-expanding aortic valve bioprosthesis-animal feasibility study // European journal of cardio-thoracic surgery. - 2009. - Vol. 36. - No. 5. - P. 813-817.). The lack of rigid support in the area of the aorto-left ventricular contact causes gross changes in the geometry of the mitral-aortic contact zone, acute mitral regurgitation immediately after the opening of the lower "skirt" of the nitinol frame. Another feature of the surgical anatomy of the animal heart is the low origin of the coronary arteries, the mouth of the left coronary artery originates at the base of the aortic sinus, which creates prerequisites for coronary circulation disorders with high positioning of the lower "skirt" of the nitinol frame. In this regard, one of the ways to solve the problem of safe positioning of the self-opening aortic valve prosthesis may be to lengthen the outflow tract of the left ventricle of the heart, impart additional rigidity to it, and also excise the native valve apparatus in order to prevent coronary blood flow disorders.

A known technique in the existing state of the art is experimental strengthening of the fibrous ring of the aortic valve to provide additional rigidity and radiopaque marking using infravalvular implantation of a silicone ring with tantalum coating and synthetic braiding. This technique is described in the work of Carney J.P. et al. (Carney J.P. et al. New model for the assessment of transcatheter aortic valve replacement devices in sheep // Journal of Investigative Surgery. - 2022. - Vol. 35. - No. 2. - Pp. 371-377.). The silicone core of the ring made it possible to open it in the case of a native fibrous ring size greater than 110 mm. However, such a technique involves a two-stage approach to implantation of a self-expanding aortic valve prosthesis and has a number of disadvantages:

1) lack of a range of sizes of implantable rings;

2) narrow landing zone, persistent risk of prosthesis migration;

3) the remaining risk of influence of the exposed prosthesis frame on intracardiac structures, mainly on the geometry of the mitral valve;

4) preservation of the native aortic valve leaflet apparatus and the risk of developing prolapse of the native leaflets;

5) pressure in the areas of localization of the cardiac conduction system.

Disclosure of the essence of the invention.

The technical problem that the claimed invention is aimed at solving is the experimental development of a method for open implantation of a self-opening aortic valve prosthesis.

The technical result of the task is achieved by creating optimal conditions for safe and reliable positioning of the valve prosthesis by removing the native leaflet apparatus and intraannular implantation of an anatomically shaped nitinol support frame. In this case, the aorta is opened with a transverse incision 0.5 cm above the sinotubular junction, continuing the incision in the direction of the non-coronary sinus. Preliminary excision of the native aortic valve cusps is performed. Using U-shaped sutures with felt pads in the area of the aortic valve commissures, a nitinol support frame is implanted in the intraannular position. After immersion and fixation of the nitinol support frame in the outlet section of the left ventricle, the posterolateral semicircles of the aortotomy access are sutured. The aortic valve prosthesis is cooled, the compressed and fixed frame of the self-expanding aortic valve prosthesis at the top is placed inside the implanted nitinol support frame and warmed by irrigation with a physiological solution at a temperature of 36°C. The ligature fixing the upper part of the self-expanding aortic valve prosthesis is removed, and the aorta is sutured.

The invention is illustrated by the images in Figs. 1–3:

Fig. 1a - stage of preparation of the self-expanding aortic valve prosthesis, passing the lavsan thread through the upper cells of the self-expanding aortic valve prosthesis;

Fig. 1b - stage of preparation of a self-opening aortic valve prosthesis, fixation in the upper part of the “crown”;

Fig. 2 – diagram of the stage of implantation of the nitinol support frame in the intraannular position;

Fig. 3 – diagram of the stage of implantation of the aortic valve prosthesis inside the implanted nitinol support frame.

The method is performed as follows.

After performing median sternotomy, access to the heart and systemic heparinization (3 mg/kg), the artificial circulation machine is connected. Artificial circulation is initiated, the heart is verticalized and the hemiazygos vein is sutured to prevent washing out of the cardioplegic solution from the posterolateral wall of the heart. Left ventricular drainage is installed through the left atrial appendage or the apex of the left ventricle. To reduce the time of artificial circulation and myocardial ischemia, a model of a self-expanding aortic valve prosthesis is prepared in advance. For this purpose, a lavsan thread 2 (Fig. 1a) is passed through the upper cells of the self-expanding aortic valve prosthesis 1 with the help of which, after cooling, the aortic valve prosthesis is compressed on the bougies and fixed in the upper part of the "crown" (Fig. 1b).

After performing cardioplegia, the aorta 3 is opened with a transverse incision 0.5 cm above the sinotubular junction, continuing the incision in the direction of the non-coronary sinus. The native cusps are removed leaving a small edge of the base. This technique allows strengthening the line of future sutures and additionally "sealing" the space between the nitinol support frame and the aortic ring. Using U-shaped sutures 4 with felt pads in the area of the aortic valve commissures, the nitinol support frame 5 is implanted in the intraannular position (Fig. 2). After immersion and fixation of the nitinol support frame in the outlet section of the left ventricle 6, the posterolateral semicircles of the aortotomy access are sutured with a mattress suture. Then the compressed and fixed in the upper part aortic valve prosthesis 1 is placed inside the implanted nitinol support frame 5 (Fig. 3) and warmed by irrigation with warm (36°C) saline solution. After expansion and self-fixation of the lower part of the prosthesis 1 inside the previously implanted nitinol support frame 5, the aortic valve prosthesis is again cooled with ice-cold (4°C) saline solution to prevent premature opening of the prosthesis "crown" and facilitate restoration of the integrity of the aorta 3. Ligature 2 fixing the "crown" of valve prosthesis 1 is removed, and the second row of sutures is completed (Fig. 3). After deaeration of the heart chambers, the transverse clamp is removed from the aorta and cardiac activity is restored. The wound is sutured layer by layer with steel sutures, leaving drains in the pleural cavities and the pericardial cavity.

The technical result provided by the given set of features consists in carrying out open implantation of a self-expanding aortic valve prosthesis, ensuring its safe and reliable positioning, preventing migration and minimizing the risk of developing life-threatening complications. The quality of open implantation of a self-expanding aortic valve prosthesis by the proposed method can be assessed after restoration of independent cardiac activity using transesophageal echocardiography (TEE), transthoracic ultrasound and/or X-ray contrast methods of examination.

An example of specific implementation.

The experiments were performed on Landrace pigs, females weighing 129.83±9 kg. Animal care, experimental support, observation and euthanasia were performed in accordance with the European Convention for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes (Strasbourg, 18.03.1986). One hour before the intervention, premedication was performed with Zoletil-100 at a dose of 5-7 mg/kg intramuscularly in the area at the base of the ear. When the target level of sedation was achieved, the animals were transported on stretchers to the preoperative preparation room, where sanitary and hygienic treatment of the surgical field was performed. Anesthesia was induced by intravenous administration of 0.005% fentanyl (0.006-0.008 mg/kg), propofol (4-6 mg/kg) and arduan (0.1-0.15 mg/kg), after which tracheal intubation was performed through the mouth using direct laryngoscopy with a blade. Anesthesia was maintained by inhalation of 2-4 vol% sevoflurane and bolus administration of 0.001-0.002 mg/kg fentanyl every 20 minutes. At the stage of artificial circulation, anesthesia was maintained by infusion of 4-6 mg/kg/hour propofol and bolus administration of 0.001-0.002 mg/kg fentanyl every 20 minutes. After tracheal intubation, the animal was transferred to artificial ventilation using the JulianPlus apparatus (Dreger, Germany). A central venous catheter was placed in the femoral vein to monitor central venous pressure and intravenous infusion. To monitor invasive arterial pressure and collect arterial blood for gas and electrolyte control, the subcutaneous artery of the inner thigh was sectioned and an arterial line was placed.

The prototype of a self-expanding aortic valve prosthesis developed at the Federal State Budgetary Institution "National Research Institute of Cardiology and Cardiology named after Academician E. N. Meshalkin" of the Ministry of Health of the Russian Federation together with Angioline LLC (Novosibirsk) was used as a model of a self-expanding valve. The frame of the prosthesis was made of titanium nickelide, which has a "shape memory" effect. The valve leaflet apparatus was made of porcine pericardium treated with epoxy compound using standard technology.

The animal was placed in a supine position and a median sternotomy was performed. After systemic heparinization (3 mg/kg), the heart-lung machine was connected. In order to preserve space for placing the transverse clamp, cardioplegic cannula and performing aortotomy, the arterial cannula (16Fr) of the heart-lung machine was installed in the right common carotid artery. A two-stage venous cannula was installed in the right atrium. Then, a self-expanding transcatheter aortic valve was implanted according to the technique described above.

In the course of the conducted series of chronic experiments, 9 open implantations of the self-expanding aortic valve were performed. In all cases, optimal positioning of the prosthesis frame was achieved. In the early postoperative period, 2 animals (22.2%) died, the main cause of death was acute heart failure. After 3 months of observation, 7 pigs (77.7%) were alive, after 6 months, the survival rate was 55.5% (5 animals). According to TEE data, no cases of aortic valve dysfunction were recorded either in the early or late postoperative periods. After the animals were withdrawn from the experiment, the valve was positioned correctly in all cases during the pathological examination, no paraaortic fistulas or impaired closure function of the prosthesis were detected during the examination of the landing zone, the coronary artery orifices were intact. According to the results of pathomorphological studies after 6 months, no cases of valve prosthesis migration were recorded. In all cases, the lower "skirt" of the frame was self-fixed in the lumen of the implanted nitinol support frame. In addition, in all cases, the leaflet apparatus of the prosthesis was not changed, the leaflets were mobile and worked correctly, the shape of the frame was preserved and the diameters coincided with the original ones. In 3 cases (33.3%), fibrous compaction was noted in the A2 segment of the mitral valve, apparently caused by the adhesion of the nitinol support frame.

Thus, the obtained data indicate that the proposed as an invention method of open implantation of a self-expanding aortic valve prosthesis by strengthening the outlet section of the left ventricle and isolating the boundaries of the permissible expansion of the aortic valve prosthesis allows avoiding the development of a number of life-threatening complications: migration of the prosthesis, impaired coronary circulation, atrioventricular block, aorto-left ventricular fistula and mitral regurgitation, and can be recommended as a routine method when conducting preclinical trials of new models of self-expanding aortic valve prostheses.

Claims (1)

A method for open implantation of a self-expanding aortic valve prosthesis in an experiment with artificial blood circulation, characterized in that the aorta is opened with a transverse incision 0.5 cm above the sinotubular junction, continuing the incision in the direction of the non-coronary sinus, excision of the native aortic valve cusps is performed and, using U-shaped sutures with felt pads in the area of the aortic valve commissures, a nitinol support frame is implanted in the intraannular position; After immersion and fixation of the nitinol support frame in the outlet section of the left ventricle, the posterolateral semicircles of the aortotomy access are sutured, then the cooled, compressed and fixed in the upper part frame of the self-expanding aortic valve prosthesis is placed inside the implanted nitinol support frame and warmed by irrigation with a physiological solution at a temperature of 36°C, the aorta is sutured.