Complete transposition of the great vessels (TGA) is the most common clinical form of neonatal cyanotic congenital heart disease with severe hypoxemia after birth, and 80% of children die within 2 months if not treated surgically. The intra-atrial transposition method (including Seening and Mustard procedures) for TGA does not resolve the anatomical malformations of the heart, and long-term follow-up reveals significantly lower right ventricular ejection fraction, afterload, and myocardial responsiveness, and greater susceptibility to aortic regurgitation, arrhythmias, and cardiac arrest [1]. arterial transposition (ASO) was first successfully accomplished by Jatene [2] in 1975, and later With the improvement of Lecompte, ASO has become the procedure of choice for the treatment of TGA. After 2 weeks of life, pulmonary artery pressure begins to physiologically decrease and left ventricular pressure decreases. Without timely intervention, disuse dysplasia of the left ventricle can occur, affecting the need for pressure in the body circulation; if accompanied by a large ventricular septal defect, it can easily lead to pathological pulmonary hypertension in children. Thus, the best time for ASO for TGA is within the first 2 weeks of life [3].Castaneda et al [4] started action pulse reversal in neonates with transposition of the great arteries in 1983. The progress of ASO procedure for neonatal TGA is reviewed as follows. Zhang Zewei, Department of Cardiac Surgery, Children’s Hospital, Zhejiang University School of Medicine
1 Preoperative preparation
1.1 Comprehensive understanding of the cardiac pathophysiological status of the child The literature reports whether the child was born prematurely. The development and function of liver, kidney, lung and brain, the presence of other malformations in combination with TGA, the anatomy of coronary arteries, and the presence of infection are still risk factors for surgery [5]. William [6] et al. concluded that the selection criteria for ASO surgery for TGA are: (1) absence of pulmonary valve and left ventricular outflow tract stenosis; (2) acceptable left ventricular development with left ventricular pressure/right ventricular pressure >0.6; (3) pulmonary vascular resistance <6Wood units/m ; (4) no severe tricuspid and mitral regurgitation; (5) no coronary artery malformation affecting the graft. Follow-up revealed that the relationship between the anatomical location of the great vessels, the size of the difference in the diameter of the pulmonary aorta, the condition of the aortopulmonary valve, and the anatomical type of the coronary artery were high-risk factors for the occurrence of aortic regurgitation, ascending aortic obstruction, pulmonary stenosis, and coronary artery stenosis after surgery. Some scholars believe that the above criteria can be appropriately relaxed, and that the configuration and pressure of the left ventricle and pulmonary vascular resistance can be improved by medical treatment, and that some pulmonary valve and left ventricular outflow tract stenosis and malformed coronary arteries can be addressed surgically [4]. It has also been suggested that with further understanding of complex coronary artery forms and further improvements in coronary anastomosis, ASO can be performed for TGA of any type of coronary artery.
1.2 Opening the arterial ducts improves cardiopulmonary function in children Many scholars reported the use of prostaglandin (PGE1) in neonates with duct-dependent congenital heart disease from the 1970s to 1980s [7].PGE1 dilates the small pulmonary arteries and arterial ducts, increasing the left atrial return blood volume, thus increasing the left atrial pressure and shunting the oxygenated blood from the left atrium to the right atrium and right ventricle via the foramen ovale or the atrial septal defect , the aortic oxygen saturation increases, thus improving hypoxemia. PGE 1 can also reduce pulmonary artery pressure and pulmonary vascular resistance by directly dilating the pulmonary microvasculature [8].
1.3 Other preoperative preparations Low-flow nasal catheter oxygen inhalation, generally 25%-30% oxygen inhalation concentration, to avoid inhalation of high oxygen concentration and induce arterial catheter spasm, resulting in low cardiac output syndrome, aggravating the condition. Inhale NO to reduce pulmonary hypertension, correct acid-base balance, and apply dexamethasone 1 d before surgery to reduce the inflammatory response induced by extracorporeal circulation and maximize the physiological condition of the child[3] .
2 Surgical methods
2.1 Decomposition of the free aorta The neonatal thymus is large and can be partially or completely removed if it affects the surgical operation; if it does not affect much, removal is not advocated to preserve its immune function. The relationship between the location of the aorta and pulmonary artery and the difference in diameter between the two major vessels and the coronary artery anatomy should be understood before the surgical operation. The ideal position of the great arteries is anterior-posterior, but often the aorta is slightly anterior to the right, while the pulmonary artery is slightly posterior to the left, and does not affect the great vessel connections. The ascending aorta is carefully freed to the innominate or left subclavian artery, and the left and right pulmonary arteries are freed to the first segmental branch of the pulmonary hilar. Adequate freeing of the aorta and pulmonary arteries not only facilitates aortic cannulation, reconstruction of the main and pulmonary arteries, and coronary artery grafting, but also facilitates the treatment of other combined malformations such as constriction of the aortic arch (COA) together [9]. In case of injury during coronary artery grafting, the left subclavian artery can be used to repair the coronary artery.
2.2 Establishment of extracorporeal circulation There are two methods to establish extracorporeal circulation: (1) the aorta, superior vena cava, and inferior vena cava are cannulated separately to start extracorporeal circulation. This is mainly suitable for those with combined ventricular septal defect (VSD) and COA. (2) Aortic cannulation and superior vena cava cannulation. It is suitable for large vessel transposition with intact ventricular septum (TGA/IVS) or combined with small membrane VSD, because the body is in low flow and low perfusion state at the time of surgery, the superior vena cava cannula combined with intracardiac suction tube to assist in attracting inferior vena cava blood, which can completely meet the systemic venous blood return to the extracorporeal circulation machine, and quickly repair the atrial septal defect (ASD) and small membrane VSD, then close the right atrial incision and perform transposition of the aorta, reducing intubation steps and saving procedure time. Hypothermia, low-flow, or circulatory arrest techniques can reduce the energy metabolism of the child and reduce the body’s oxygen demand, which is beneficial for brain and myocardial preservation. However, the delayed inflammatory response induced by hypothermia, low flow or stopping circulation can lead to organ insufficiency, impaired brain development, slow rewarming, microcirculatory changes and cellular damage [11].Pouard et al [12] concluded that normothermic extracorporeal circulation can be more favorable for neonates undergoing ASO and reduce surgical complications. During normothermic extracorporeal circulation, the child’s body temperature is maintained at 35°C to 36°C, and thermal myocardial protective fluid is infused once every 10 min for 1 min or temporarily when the myocardium is electrically active, and postoperative modified ultrafiltration is routinely performed.
2.3 Coronary artery grafting Coronary artery grafting is the key to ASO. The small infant heart is much smaller than the adult heart, and the myocardium contains more water and is more tender. Intracardiac surgical operations require greater delicacy and accuracy, and excessive and inappropriate operations can cause coronary artery and epicardial bleeding and injury, all of which may lead to coronary artery stenosis and compression, resulting in myocardial infarction or sudden death [13]. The basic technique of coronary artery grafting: the coronary button is cut as large as possible, and even almost the entire portion of the aortic wall of the lacking sinus, including the coronary opening, may be cut to form a large coronary button in order to lengthen the coronary artery. For normal alignment coronary arteries only the coronary trunk usually needs to be free, whereas for coronary arteries with abnormal loop alignment it is usually necessary to free to the beginning of the first branch of the coronary artery to avoid twisting or traction during grafting [14]. Several grafting techniques for complex coronary artery anomalies: (1) “Live plate gate” incision of the pulmonary artery: suitable for early branching of the coronary artery, especially for early branching of the conical branch of the left coronary artery [15] (2) “Convex window” technique: suitable for coronary arteries with no or short coronary trunks or multiple openings trunk or multiple openings [16]; (3) pericardial or pulmonary artery hood enlargement technique: this method can be applied in cases where the aorta and pulmonary artery do not match in size and the coronary graft may or has caused distortion or ischemia requiring adjustment of the coronary anastomosis position [17]; (4) intramural coronary artery graft: the button containing two coronary openings is rotated or the intramural branch is de-topped so that the two openings obtain a certain distance apart and then graft them separately [14]; (5) in situ coronary artery graft: it is suitable for any kind of coronary artery malformation and aortic and pulmonary artery location relationship [18]. Coronary artery anastomosis is generally performed abroad with 5-0 or 6-0 Prolene sutures, and in China, 6-0 or 7-0 Prolene sutures are generally used. After the new aortic anastomosis is completed, the perfusion of the left and right coronary arteries is carefully checked after venting and opening to ensure that the myocardium is red in color and there are no dark areas of ischemia. With improved and enhanced surgical techniques, although coronary artery grafting is no longer an independent surgical risk factor, injury and distortion during coronary artery grafting, post-graft compression, and malformed coronary arteries are still important causes of distant reoperation and myocardial ischemic death [19].Chang et al [15, 17] concluded that selecting the appropriate position of the coronary button after the completion of the neonatal aortic anastomosis significantly reduced the occurrence of poor coronary artery displacement and reduced complications and mortality of coronary grafts.
2-4 Shortening the operation time and timely opening of the aorta Juan et al [5] reported that extracorporeal circulation time, aortic block time, and cardiac arrest time are risk factors for other comorbidities after ASO surgery, so it is advocated to minimize the operation steps, skillful operation, strengthen myocardial protection, and rewarming and vent opening after new aortic reconstruction to make the heart beat early. The postoperative recovery of left heart function is the basis for judging the success of surgery. Monitoring left atrial pressure is important for understanding left heart function, body circulation pressure and circulating blood volume, therefore, a left atrial manometry tube should be routinely placed after surgery, and there are two ways to place the manometry tube: (1) via the atrial septum from the right atrium; (2) directly inserted from the left auricle, taking care not to damage the left superior pulmonary vein.
2.5 Pacemaker use Myocardial edema, poor myocardial perfusion, reduced myocardial energy metabolism, and disturbances in the internal environment caused by stressful stimuli such as extracorporeal circulation and surgery are the main causes of arrhythmias. Some arrhythmias are not clinically symptomatic but can cause fatal comorbidities such as syncope, stroke and sudden death. Therefore, it is recommended to routinely place pacing leads in children with combined VSD, closely monitor the rhythm, and promptly administer medication or place permanent pacemakers to reduce the incidence of postoperative arrhythmias.
3 Postoperative downtime
3.1 Maintain circulatory stability Because the myocardium is in the stentorian phase and the left ventricle begins to readapt to the body circulation in the early stages of cardiac resuscitation, vasoactive drugs can be applied after the heart beats at the end of surgery. Maintain left atrial pressure (LAP) 6-10 mmHg (1 mmHg = 0.133 kPa), central venous pressure (CVP) 7-13 emil O, mean arterial pressure (MAP) 40-70 mmHg, pulse pressure difference >15 mmHg, heart rhythm 135-190 beats/min. dobutamine and dobutamine 3-5 g/(kg/min) are continuously pumped. If blood pressure is still difficult to maintain, and with edema and low urine, epinephrine 0.03-0.50 g/(kg/min), milrinone 0.30-0.75 g/(kg/rain), and active calcium 1 ml/(kg/h) can be added [19]. The combination of vasoactive drugs exerts positive inotropic effects while causing relaxation and expansion of arterial and venous vascular smooth muscle, reducing the resistance of the body and pulmonary circulation, increasing myocardial blood displacement, and reducing myocardial work. In addition, the central static teaching pump pumps platelets, gives human thrombospondin complex to stop bleeding, and fisetin to neutralize heparin.ASO surgery time is long, there is obvious fluid accumulation and inflammatory reaction in children after extracorporeal circulation, and the neonatal kidney and lung development is incomplete, the compensatory capacity is weak, so we should strengthen post-surgical ultrafiltration, filter out excess water and inflammatory mediators in the blood, improve blood colloid osmotic pressure, so that the hematocrit ( HCT) is maintained at 0.30-0.35 to avoid low cardiac output, capillary leakage and sodium retention [21].
3.2 Delayed chest closure (DSC) The concept of DSC after cardiac surgery was introduced by Riahi et al [22] in 1975 and was first used in adults after open-heart surgery to prop up the sternum to reduce cardiac compression symptoms.McElhinney et al [23] concluded that DSC can effectively address the problem of mediastinal compression after neonatal cardiac surgery.The long duration of ASO surgery, severe myocardial edema, pulmonary edema, and Routine chest closure will compress the heart and
affects blood circulation; the child’s blood pressure and oxygen saturation are unstable, and chest compressions may be opened at any time; DSC can be considered with auxiliary devices, such as extracorporeal membrane pulmonary oxygenation (ECMO) to assist cardiac and pulmonary function after surgery [24]. Two 3- to 4-cm-long support rods are made from extracorporeal circulation tubes or 5 ml syringe syringes for neonates, and the ends are cut into grooves to nestle the sternum, and the support rods are fixed to the edge of the sternum with nonabsorbable sutures. The sternal cavity is isolated from the outside world in two ways: (1) by suturing the skin edges of the sternal incision relatively continuously; (2) by suturing the skin edges continuously with Gore-tex patches and then covering them with a transparent silicone film.DSC generally lasts 2-3 d and is performed after the child is hemodynamically stable, the myocardial edema dissipates, there is no bleeding, and the ancillary equipment is evacuated [25].
4 Other surgical advances
4.1 Application of ECMO After surgery, the child’s cardiopulmonary function cannot be well recovered, blood pressure, heart rhythm, heart rate, oxygen saturation is unstable, urine output is low, complicated by low cardiac output, conventional treatment is ineffective, and it is impossible to get out of extracorporeal circulation, while the child’s cardiac malformation has been corrected and the lung lesion is reversible, at this time, ECMO should be considered for support to replace the pulmonary gas exchange task and cardiac pumping function, so that the heart and lungs get adequate rest to provide valuable time for recovery of cardiac and pulmonary function [26].ECMO was first applied to neonates in 1974.The selection criteria for ECMO in neonates: gestational age >34 weeks, weight >2000 g, absence of active bleeding and severe coagulopathy, absence of fatal anatomical malformations after surgery, and reversible pulmonary pathology [27]. Postoperative cardiopulmonary support in neonates after cardiac surgery was performed using a veno-arterial (V-A), right atrium-aorta model. Postoperatively, if shutdown is not possible, ECMO is established using the original cardiac cannula, and the transition is made directly from extracorporeal circulation to ECMO. Return to the care unit for treatment.
4.2 Prevention and treatment of caviar protein toxic reactions Currently, with the improvement of extracorporeal circulation and cardiac surgery techniques, the surgical morbidity and mortality rate has decreased significantly, while severe toxic reactions caused by caviar protein are becoming one of the important causes of death in patients undergoing cardiac surgery. Neonates with immature liver, kidney and lung functions are more susceptible to ichthyosperm protein toxic reactions. Clinically, ichthyosperm protein toxic reactions are characterized by sudden slowing of heart rate, weakness of myocardial contraction, decrease in blood pressure, decrease in cardiac output, increase in pulmonary vascular resistance, increase in pulmonary artery pressure, increase in airway pressure, right heart expansion, and foamy bloody sputum 5-10 min after ichthyosperm protein input. The mechanisms of ichthyospermins toxic reactions are mainly myocardial damage caused directly by ichthyospermins; pulmonary vasoconstriction and pulmonary hypertension caused by activation of complement and immune complexes by allergic reactions; and NO production by abnormal surrogates in the body circulation caused by excess ichthyospermins resulting in a decrease in body circulation pressure [28-30]. For the prevention and management of toxic reactions to ichthyospermins, scholars at home and abroad have conducted a large number of studies, based on the mechanism and pathological process of its occurrence, advocating (1) monitoring the activated coagulation time (ACT)/activated partial thromboplastin time (AfyITr) and precise dosage; (2) pumping human ichthyospermins from peripheral veins or aortic roots in small doses; (3) decisive management of ichthyospermins toxic reactions: for those with severe low cardiac arrhythmia syndrome or cardiac arrest, immediately transfer to secondary assisted circulation, while applying antihypertensive drugs and positive inotropic drugs to strengthen the protection of brain, heart, lung and kidney functions, and assist for a long enough time to fully recover heart, lung, kidney and vascular functions; (4) input fisetin after the child’s heart rhythm and heart rate are stable, the heart muscle contraction is strong, the circulation is stable and the blood oxygen saturation is satisfactory; (5 ) using low molecular weight fisetin with low toxic reactions [31-32]. With the advancement of anesthesia and surgical monitoring theory, the development and improvement of extracorporeal circulation and surgical skills, the success rate of surgery for neonatal transposition of large vessels will become higher and higher, and children who were inoperable in the past can be saved. However, coronary artery malformation, poor development of the two major vessels, combined cardiac malformation, prolonged extracorporeal circulation, aortic block, and cardiac arrest are still factors that affect surgery. Postoperative occurrence of coronary stenosis, aortic regurgitation, pulmonary stenosis, arrhythmias, and neurodevelopmental dysplasia are the main problems that need to be addressed in today’s surgery.
(Zhang Zewei)
5 REFERENCES
[1] Szyma^ski P, Hofman P, Lubiszewska B, et a1. The relationship between blood pressure,pulse pressure and right ventricular function following an atrial switch procedure for complete transposition of the great arteries [J].International Journal of Cardiology, 2005. 101(1):59-63
[2] Jatene A D, Fontes V F, Paulista P P, et al Anatomic correction of transposition of the g reat vessels [J].Thorac Cardiovasc Surg. 1976, 72(3):364 -370
[3] Brian W, Nancy C. Roger B. et al, Selective timing for the arterial switch operation [J]. The Annals of Thoracic Surgery, 2004. 77(5): 1691 -1696
[41 Castaneda, Thomas H J, Steven D, et al The hemodynamic results Of the arteriaI switch operation in neonates with transposition of the great arteries and intact ventricular septum [J]. American Heart Journal, 1985, 1 10(3):704.
[5] Juan A. Hem d ndez G. Valladares C M. et al Risk Factors Associated With ArteriaI Switch Operation For Transposition Of The Great Arteries [J].Revista Espanola de Cardiologia. 2005, 58(7): 815-821
[6] Williams W G McCrindle B W Ashburn D A, et a1. Outcomes of 829 neonates with complete transposition of the great arteries 1 2-1 7 years after repair [J]. European Journal of Cardio-Thoracic Surgery, 2003, 24(1):1-10
[7] Host A. Halken S, Kamper J, et al Prostagtandin E1 treatment inductu dependent congenital cardiac malformation: a review of thetreatment of 34 neonates [J] Dan Med Bull, 1988, 35(1): 81-84
[8] Shen J, He B, Wang B. Efects of lipo-prostagtandin E1 on pulmonary hemodynamics and clinical outcomes in patients with pulmonary arterial hype rcension [J]. Chest. 2005, 28(2):714-719
[9] Pocar M, Villa E, Degandt A, et a1. Long-Term Results After P rimarv One-Stage Repai r of Transposition of the Great Arteries and Aortic Arch Obstruction [J] Journal of the American College of Cardiology, 2005, 46(7):1331-1338
[10] Sung S C, Chang Y H. Lee H D, et aI Left subclavian artery free graft as a salvage technique after failed coronary artery transfer in arterial switch operation [J].European Journal of Cardio-Thoracic Surgery.2005, 27(3):515-517
[11] Wypij D, Newbu rger W, Rappapod J, et al The effect of duration of deep hypothermic ci rculatory arrest in infant heart surge ry on late neurodevelopment: the Boston Ci rculatory Arrest Trial [J] Journal of Thoracic and CardioVascular Surgery.
2003. 126(5):1397-1403
[12] Pouard P, Mau riat P, EK F, et al Normothe rmoic Cardiopumonary bypass and myocardial Cardioplegic protection for neonatal arterial switch operation [J]. European Journal of Cardio-thoracic Surguery, 2006, 30: 695-699
[13] Bartoloni G, Bianca S, Patan e L, et al Pathology of coronary narrowing after arterial switch operation: autopsy findings in two patients who died within 3 months of surgical treatment and review of the literature [J] CaraiovascuIar Pathology, 2006, 15(1): 49-54
[14] Sung S C, Chang Y H, Lee H D, et a1. Arterial switch operation fo r transposition of the g reat arte ries with coronary arteries from a single aortic sinus[ J] The Annals of Thoracic Su rgery, 2005, 80(2):636-641
[15] Chang Y H, Sung S C, Lee H D, et al Coronary Reimplantation after neoaortic reconstruction can yield better result in arterial switch ope ration. comparison with open “trap door technique[J].The Annals of Thoracic Surgery, 2005. 8O(5):1634-1640
[16] Yamagishi M, Shuntoh K, Fujiwara K, et al “Bay window technique for the arterial switch operation of the transposition of the great arteries with complex coronary arteries [J] Ann Thorac Surg, 2003, 75(6): 1769-1774
[17] Tireli E, Korkut A K, Basaran M, et at Implantation of the coronary arteries after reconstruction of the neoaoGa by using “pe ricardial A significant impact on the outcome of arterial switch operations[J]l
Cardiovasc Surg. 2003. 44(2):173-178.530
[18] Murthy K S, Coelho R, Kulkarni S, et al Arterial switch operation with in situ coronary realtocation for transposition of great arteries with single coronary artery [J].Eropean Journal of Cardio-thoracic Surgery, 2004. 25: 246-249.
[19] Sarris G E, Chatzis A C, Nicolas M, et aI The arterial switch operation in europe for transposition of the great arteries: a multi-institutional study from the european congenital heart surgeons association [J]. The Journal of Thoracic and Cardiovascular Surgery. 2006, 1 32(3): 633-639
[20] Hayashi G, Kurosaki K, Echigo S, et at P revalence of Arrhythmias and their risk factors mid- and tong-term after the arterial switch operation [J]. Pediat Cardial, 2006, 27: 689-694
[21] Bord S D. Cherry C, Hickey C The arte rial switch p rocedure for transposition of the great arteries [J]. Aorn, 2007, 86(2):211-230.
[22] Hiahi M, Tomatis L A, Schlosser R T Cardia compression due to closure of the median sternotomy in open-hear surgery [J].Chest. 1975. 67: 113-114
[23] McEIhinney D B, Reddy V M. Parry A J, et al Management and outcomes of delayed sternal closure after cardiac surge ry in neonates and infants [J] Crit Care Med. 2000. 28: 118O 1,184
[24] Samir K, Misawa Y, Ribe ri A, et aI. What can be an indicator of delayed sternal closure after cardiac su rgery [J]?Eu r J Car-diothorac Surg, 2002, 22(3):493-496
[25] Riphagen S, McDougalt M, Tibby S M, et al “Early delayed sternal closure following pediatric cardiac surgery [J].Ann Thorac Surg, 2005, 80(2):678-84.
[26] Ferns S J. Neonatal myocardial infarction and the role extracorporeal membrane oxygenation (ECM0) [J] Arch Dis Child Fetal Neonatal Ed. 2007, 23(1):334-339
[27] Thiagarajan R R. Extracorporeal membrane oxygenation to aid cardiopulmonary resuscitation in infants and child ren [J] Circutation, 2007. 24{3): 378-381
[28] Anesth Analg. Protamine contributes to myocardial ischemia [J].Anesthesiology. 2005, 103(3):669
[29] Friedman M, Johnson R, Wang S. et al PuImonary micro-vascular responses to p rotamine and histamine [J] Thorac Cardiovasc Surg, 2006, 54(8):506-511
[30] Takakura K, Mizogami M. Fukuda S Protamine sulfate causes endothetium-independent vasoretaxation via inducible nit ricoxide synthase pathway [J] Anaesth, 2006, 53(2):162-167
[31] Herr H A, Jobes D R. Tenhav E T Averse events after protamine administration following caraiOpufmOnary bypass in infants and children [J]. Anesth A nalg, 2003, 97(2):283-389
[32] Wu H B, Wang Z W, Cheng D L, et al,Occurrence and management of toxic reactions to fisetin in direct cardiac surgery [J].Chinese Clinical Journal of Thoracic and Cardiovascular Surgery, 2007, 14(3);230-231