1.Objects and methods
1.1 Study subjects
There were 16 males and 2 females in the group, with ages ranging from 5 to 66 years, averaging 36.8 years; body weights ranging from 20 to 75 kg, averaging 58.4 kg. There were 17 cases of aortic valve disease (8 cases of congenital valvular malformation and 9 cases of rheumatic valve disease), 5 cases of aortic valve stenosis (including 1 case of combined bacterial endocarditis and 1 case of coronary heart disease), 5 cases of aortic valve insufficiency (including 2 cases of combined mitral valve insufficiency), and 7 cases of aortic valve stenosis and insufficiency (including 1 case of combined bacterial endocarditis and 1 case of mitral valve insufficiency). Two cases), 7 cases of aortic stenosis and insufficiency (including 1 case of combined bacterial endocarditis and 1 case of mitral insufficiency), and 1 case of complete transposition of the great arteries and double outlet of the right ventricle.
Preoperative cardiac function was grade II in 14 cases and grade III in 4 cases. Chest radiographs mostly indicated left ventricular involvement, and electrocardiograms indicated left ventricular hypertrophy and ST-T changes. Preoperative echocardiogram showed left ventricular end-diastolic within.
1.2 Materials
Homozygous valved aorta was taken from homozygous valve bank and preserved by antibiotic sterilization freezing and liquid nitrogen freezing methods. Once identified for use during surgery, they were removed from the liquid nitrogen tank, thawed in warm water (40°C), thawed completely for about 15 min, and then rinsed 2 to 3 times in cold saline before being prepared for use.
1.3 Method surgery
It was done under general anesthesia with hypothermic extracorporeal circulation. Endotracheal intubation, intravenous compound anesthesia, median sternotomy, routine aortic cannulation of the ascending aorta, and superior and inferior vena cava cannulation via the right atrium to establish extracorporeal circulation. The whole body was moderately hypothermic, and cold crystalloid cardioplegia solution was instilled via the root of the ascending aorta, or cold blood stop solution was instilled, and ice chips were applied around the heart.
Aortic valve replacement in 16 cases: the inner diameter and annulus of the homogeneous aorta were selected to be 2-4 mm smaller than the inner diameter of the recipient aorta, the diseased aortic valve leaflets of the recipient were cut out, 3 stitches were sewn at the 3 junctions to support the 3 junctions opposite the 3 junctions of the donor-recipient in turn, the 3 junctions corresponding to the lower edge of the homogeneous valve were threaded, and then the homogeneous valve was turned into the left ventricle and the lower edge was fixed in the recipient with 3-0 prolene sutures continuously The aortic annulus was then turned out in normal form, and the upper edge was sutured to the recipient aortic wall with 4-0prolene continuous sutures.
In two cases, the aortic root was enlarged because of the small aortic annulus, and mitral valvuloplasty and coronary artery bypass grafting were performed in one case each at the same time. 1 case of Ross procedure: 4-0prolene continuous sutures were used for both upper and lower margins, and the homograft aortic valve was grafted to the pulmonary root, and the autologous pulmonary valve was grafted to the aortic root at the same time. 1 case of Rastelli procedure: the homograft aortic valve was used for external suturing. One case of Rastelli operation: the same kind of valved aorta was used as the external conduit, and the proximal and distal ends were anastomosed with 4-0prolene continuous sutures, and the combined other intracardiac malformations were corrected in one stage.
The extracorporeal circulation time of this group ranged from 92 to 357(159.1±58.4) min, and the aortic block time ranged from 74 to 205(120.9±33.0) min.
2, Results
One case of early postoperative death: the patient with Rastelli surgery died due to severe hypocapnia; the rest recovered, one of which had 2 postoperative open-heart hemostasis. Postoperative tracheal intubation time was (20.6±8.8)h and ICU stay was (43.5±18.6)h.
The postoperative echocardiogram showed that LVIDD (51.2±11.7)mm, LVIDS (37.2±8.5)mm, LVEF (58.1±16.6)%, LVFS (31.8±12.7)%. 1 case had a small amount of pericardial effusion, which was absorbed after the application of cardiotonic diuretic drugs; 1 case had a small amount of regurgitation of the same valve after surgery, but the rest had no abnormality, and the valve function was good. The rest had no abnormalities and good valve function. One case was followed up for 2-10 years, but one case had a second operation to replace the mechanical valve one year after aortic valve replacement due to severe valve destruction of the homograft valve, and died of multi-organ system failure 18 d after the operation, while the rest of the patients had good postoperative survival.
3. Discussion
There are many types of extracardiac pipeline materials that can be used in the treatment of heart disease, including homogeneous and different species of biomaterials, artificial blood vessels, with and without valves, and different collection, processing, preservation, and application techniques. The controversy lies in the type and effect of the graft material, the improvement of surgical technique and the management of postoperative comorbidities. There are five main types of cardiac surgical conduits currently in clinical use.
Prosthetic vessels without valves: Gore-Tex vessels are commonly used, but their postoperative recovery is relatively difficult, and the lack of an effective pulmonary valve is a very important factor, especially when pulmonary hypertension crisis occurs in the early postoperative period.
Prosthetic vessels with mechanical and biological valves: implantation of this material (especially in children) is more prone to early valve calcification, neointimal formation and hyperplasia within the prosthetic vessel causing vascular obstruction with suboptimal results, and mechanical valves also require lifelong anticoagulation.
Porcine aortic and pulmonary artery valved conduits, bovine jugular vein valved conduits (able to obtain conduits of any caliber from 8 to 22 mm) [5]; porcine aortic and pulmonary valves + bovine pericardial conduits [6]; equine pericardial fabricated valved conduits [7].
Valved conduits made from autologous pericardium [8]: the advantage is low cost, but not suitable when there are adhesions in the pericardium or for secondary surgery.
Homogeneous conduits: homogeneous conduits, cryopreserved and active. Cryopreserved homogeneous extracardiac conduits with valves have the advantages of biological activity and tissue structural integrity, ease of use, good hemodynamics, intact valve function, long valve life, and no anticoagulation. It ensures the patency of the pipeline after transplantation, basically conforms to the anatomical structure of the normal heart, corrects cardiac malformations anatomically and hemodynamically, facilitates the recovery of cardiac function, and is less likely to develop right-sided heart failure. In contrast, complications such as bacterial endocarditis and hemolysis caused by placement are rare [9].
Currently, the use of homograft valves as patches in the right ventricular outflow tract has been recognized by a wide range of scholars, but their use as tubes in cardiac surgery has rarely been reported. Based on the experience of our group, the application of this material is completely feasible and effective.
Most scholars believe that degeneration and calcification of homografted extravalvular conduits have a direct and important relationship with immunity, and also found that degeneration after transplantation is related to the age of the recipient, the younger the age, the greater the risk of degeneration, and is related to the immune status of infants and children more likely to mediate inflammatory and immune reactions. The risk of degeneration after transplantation was also found to be related to the age of the recipient, and the younger the recipient, the greater the risk of degeneration. Endothelial cell activity plays an important barrier role in the durability of human homogeneous valves and is the most immunogenic tissue component. The deep cryogenic liquid nitrogen preservation, which is mostly used today, significantly improves endothelial cell activity and tissue structural integrity, but also significantly enhances immunogenicity. Therefore, it is best to perform ABO matching first for transplantation of homozygous valve-bearing aorta.
With the development of cardiac surgery and other disciplines, many scholars have conducted a lot of researches to explore the best way to improve the efficacy of homograft pipeline transplantation, and to prolong the service life of homograft by forming homograft flap, strengthening the protection of homograft flap and improving the preservation method, using small dose of immunosuppression, and matching ABO and HLA antigens to reduce the immune reaction after transplantation to achieve better clinical outcomes. The maturation of genetic engineering technology is expected to induce immune tolerance and mitigate immune response through molecular biology techniques.
Emerging tissue engineering techniques [10] are expected to construct recipient endothelialized tissue-engineered flap tubes by implanting recipient-derived endothelial cells onto either decellularized homografted flap tubes with intact stroma or degradable synthetic materials, which will be ideal biologic graft materials and valve replacements for the treatment of heart disease.