What is ductus arteriosus:
The ductus arteriosus is a physiological blood flow channel between the root of the left pulmonary artery and the aortic arch during fetal life. The fetus is in the mother’s amniotic fluid, the lungs have no respiratory function and are atrophied, there is no air in the lungs, and the oxygenation of venous blood does not take place. The fetus lives. After birth, from the time the baby cries, the lungs expand and inflate, and the alveoli begin to exchange air. With the development of pulmonary respiratory function and pulmonary vascular expansion, the pulmonary vascular resistance decreases significantly, and the blood flow through the arterial duct is greatly reduced, and the arterial duct gradually closes through pulmonary circulation to the left heart with disuse atrophy. Most of them close functionally 15 to 20 hours after birth. In most infants, the atresia degenerates into the ductus arteriosus ligament after 4 weeks of life.
The disease can be combined with other congenital heart diseases, such as aortic constriction, large vessel misalignment, pulmonary artery stenosis, and atrial septal or ventricular septal defects.
Pathophysiology of arteriovenous ductus arteriosus.
After birth, aortic pressure rises and pulmonary artery resistance falls. Aortic pressure exceeds pulmonary artery, whether systolic or diastolic, and aortic blood flows continuously through the ductus arteriosus to the pulmonary artery, forming a left-to-right shunt. The size of the shunt depends on the pressure step difference between the aorta and the pulmonary artery and the thickness of the catheter. The left atrial return blood volume increases and the left heart volume load increases, leading to left heart enlargement and even left heart failure. Due to the increased pulmonary blood volume, the pressure in the pulmonary circulation increases and the burden on the right heart increases, resulting in hypertrophy of the right heart. When the pulmonary artery pressure is equal to the aortic diastolic pressure, only the systolic shunt exists. When the pressure approaches or exceeds the aortic pressure, there is a bidirectional or right-to-left shunt, and clinically cyanosis develops, resulting in Eisenmenger’s syndrome and eventually right heart failure and death.
Anatomic features of an unclosed arterial duct.
The unclosed ductus arteriosus is usually located in the ductal triangle formed by the bifurcation of the aortic isthmus from the main pulmonary artery to the side of the left pulmonary artery, where the pulmonary artery, vagus nerve, and phrenic nerve travel. In a few patients with a right-positioned aortic arch, the duct may be located between the aorta distal to the root of the innominate artery and the right pulmonary artery. The left recurrent laryngeal nerve, after dividing from the vagus nerve, travels immediately around the lower edge of the catheter and up the esophageal and tracheal grooves, which is a tissue that can be easily mistaken during surgery. The first two types are more common, especially the canal type.
Clinical manifestations.
Clinical symptoms are related to the thickness of the duct, the size of the fractional flow and pulmonary vascular resistance. Fine ducts and small fractional flow are often asymptomatic; thick ducts and large fractional flow have obvious symptoms and are prone to pulmonary infections, shortness of breath, malaise, dysplasia or recurrent heart failure, and differential cyanosis. A few have dysplasia, and some may develop infective endarteritis.
Physical examination: The most prominent sign is a loud continuous machine-like murmur between the 2nd ribs at the left border of the sternum, occupying almost the entire systolic and diastolic periods, being loudest at the end of the systolic period and accompanied by tremors that propagate to the neck and back. In infants with pulmonary hypertension or congestive heart failure, there may be no continuous murmur and only a systolic murmur or no significant murmur due to changes in the pressure step difference between the aorta and the pulmonary artery.
Patients with high fractional flow may have an enlarged turbinate and increased apical pulsation. Diastolic murmurs in the apical region are present due to relative mitral stenosis. The second heart sound in the pulmonary valve region is augmented or split, but is mostly obscured by the murmur and not easily heard. Signs of the peripheral circulation that resemble aortic valve insufficiency include widened pulse pressure, watery pulse, capillary pulsation, and peripheral arterial gunshot sounds.
In a small number of patients with concomitant significant pulmonary hypertension causing a right-to-left shunt, a diastolic blowing murmur is heard only in the pulmonary artery region due to relative pulmonary valve insufficiency, and differential cyanosis is present.
Laboratory tests.
(i) X-ray examination.
In those with small catheters, the lung film is normal or the pulmonary blood is mildly increased, or only a mild enlargement of the left ventricle is seen. In pulmonary hypertension, the right ventricle can also be significantly enlarged, with the phenomenon of “dancing lung door” under fluoroscopy.
(ii) Electrocardiography.
There are four types of changes: normal, left ventricular hypertrophy, right and left ventricular hypertrophy, and right ventricular hypertrophy, both of which are accompanied by a corresponding degree of pulmonary hypertension.
(iii) Echocardiography.
Enlarged left atrial and left ventricular internal diameters and increased mitral valve activity and velocity can be seen. Two-dimensional echocardiography may reveal an unclosed ductus arteriosus.
Color Doppler flow imaging can detect abnormal blood signals from the descending aorta through the unclosed ductus arteriosus into the pulmonary artery.
(iv) Cardiac catheterization.
The main findings of right heart catheterization are higher oxygen levels in the pulmonary artery than in the right ventricle, increased pulmonary blood flow, and possibly normal or slightly increased pulmonary artery and right ventricular pressures, with cardiac catheterization from the pulmonary artery into the descending aorta via an unclosed arterial duct. Those with significantly increased pulmonary artery pressure may have bidirectional or right-to-left shunts, at which time arterial oxygen, especially in the lower extremity arteries, is reduced.
(v) Selective cardiovascular angiography.
Selective aortography can be seen with the aortic arch visualized along with the pulmonary artery, and sometimes the unclosed ductus arteriosus and the aorta at the attachment of the ductus arteriosus can be visualized with a localized funnel-like expansion, and sometimes the ascending aorta and aortic arch in the proximal segment are dilated while the aorta in the distal segment has a thin diameter.
Diagnosis and differential diagnosis: Based on the nature and location of the murmur, peripheral vascular signs, combined with echocardiography, X-ray chest film and electrocardiographic changes, the diagnosis is usually not difficult. A right heart catheterization or (and) aortography is required in atypical cases. The finding of elevated pulmonary artery oxygen levels, right heart catheterization into the descending aorta or aortography showing arterial ductus and pulmonary artery shadowing can help to clarify the diagnosis.
Arteriovenous ductus arteriosus needs to be differentiated from other conditions that cause a continuous cardiac murmur, such as.
(a) Congenital aorto-pulmonary septal defect is caused by hypoplastic aortic septum during fetal life, which leaves a defect at the aorto-pulmonary septum, and its clinical presentation is similar to that of a large ductus arteriosus, making differential diagnosis extremely difficult. A continuous machine-like murmur that is louder and lower in location (one intercostal space lower) can be used as a reference for differential diagnosis, but is not reliable. A more reliable differential is a right heart catheterization with the cardiac catheter entering the ascending part of the aorta from the pulmonary artery. Retrograde ascending aortogram, seen with simultaneous visualization of the ascending aorta and the pulmonary artery. Two-dimensional echocardiography, which shows widening of both the common pulmonary artery and the aorta with a defective communication between them, also helps in the diagnosis. In addition, if severe pulmonary hypertension occurs, there is a right-to-left shunt with cyanosis, and the blood oxygen content of its upper and lower extremity arteries is equal, which is different from that of an arterial catheterization.
(b) Ruptured aortic sinus aneurysms arising from congenital malformations, syphilis or infective endocarditis can erode and penetrate into the pulmonary artery, right atrium or right ventricle, thus causing a left-to-right shunt. The continuous machine-like murmur is similar to that of an unclosed arterial duct, but is located one or two intercostal spaces lower. The disease is most often diagnosed with a history of sudden onset, such as sudden palpitations, chest pain, chest tightness or chest discomfort, and sensation of tremor in the left chest, followed by manifestations of right heart failure, which may aid in the diagnosis.
Treatment.
Arteriovenous ductus arteriosus in premature infants can be closed naturally after birth until mature age, so asymptomatic patients can be left untreated. dl), or urea nitrogen >7, 1 mmol/l (20mg/dl ), bleeding tendency, platelets < 50×109/l or suspected necrotizing small intestinal colitis are contraindicated. or aspirin 20 mg/kg every 6 hours for four treatments, arterial catheter closure is possible within 24 to 30 hours. Those who are not treated with anti-inflammatory pain or have contraindications should be promptly treated surgically.
(A) Indications for surgery Under current conditions, the risk of surgical treatment of this disease is very small, and the surgical mortality rate is close to 0.5~1.0%. In addition to the feasible intervention for some children with 0,3~0,8 cm diameter arteriovenous catheter failure, most patients should be operated upon diagnosis. Those with symptoms should be operated early. If the catheter is thin, asymptomatic, and does not affect development, surgery should be performed before school age (2-5 years). Pulmonary arterial hypertension should be operated as early as possible. Premature infants, infants and children with recurrent pneumonia, respiratory distress and heart failure, which cannot be easily controlled with medication, should be considered for surgery in time. In cases of combined bacterial endocarditis, antibiotic treatment is usually required first, and surgery should be performed after 4-8 weeks of infection control. If the infection cannot be controlled by drug treatment, especially if there is redundant shedding, repeated arterial embolism, or pseudoaneurysm formation, surgery should be performed promptly.
(2) Contraindications to surgery 1. Combined with severe pulmonary hypertension, a right-to-left shunt has been formed mainly, the clinical appearance of differential cyanosis, the arterial catheter has become the right heart drainage channel, contraindicating surgery.
2. In complex congenital heart disease, the presence of unclosed arterial duct as a compensatory channel, such as pulmonary atresia, tetralogy of Fallot, interrupted aortic arch, misaligned aorta, etc. At this time, arteriovenous catheter nonocclusion is the only or important way for low oxygen saturation blood to enter the lungs for oxygenation and, prior to radical surgery for complex congenital heart disease, catheter closure cannot be performed alone.
(C) Preoperative preparation.
1, comprehensive and detailed medical history and relevant examinations, to clarify the presence of combined malformations and complications, and determine the surgical plan according to the results.
2, patients with severe pulmonary hypertension, even a small amount of right-to-left shunt, preoperative oxygen therapy (each min, 2 times a day) and the application of vasodilator drugs (such as prostaglandin E, sodium nitroprusside, phentolamine, etc.), conducive to the decline of whole lung resistance, creating conditions for surgical treatment.
3, combined with heart failure, give active cardiac and diuretic treatment, and wait for heart failure control before surgery.
4.Patients with pulmonary and respiratory tract infections, prompt anti-infection treatment, and surgery after the infection is cured.
5, bacterial endocardial patients, preoperative blood bacterial culture and drug sensitivity test should be made, and strengthen anti-infection treatment, infection control before surgery. If the infection cannot be controlled or recurrent embolism occurs, surgery should be performed at the same time as anti-infection and elective surgery.
(D) Preoperative communication:
The patient and family must be explained the necessity of surgery and possible risks and complications such as hemorrhage, hoarseness, catheter recanalization, perfused lung, etc. before surgery, and only if the patient and family fully understand and agree to the surgery.
(E) Surgical methods.
Currently, the commonly used surgical methods are divided into left lateral thoracotomy ligation, left lateral thoracotomy cut-off suture, left lateral thoracotomy clamp closure, median sternotomy arterial duct unclosed ligation, and transpulmonary artery duct closure under extracorporeal circulation. Among them, left lateral thoracotomy ligation and transpulmonary artery catheter closure under extracorporeal circulation are most commonly used. In recent years, there are also interventional methods to occlude the unclosed arterial duct by delivering sponge-like plastic plugs, umbrella-like, button-like or spring-like patches to the unclosed duct through cardiac catheterization, which eliminates the need for open-heart surgery, but this operation cannot completely replace open-heart surgery yet.
1. Lateral left thoracotomy ligation (1) Anesthesia and position Endotracheal intubation with intravenous compound anesthesia.
The right side is lying at 90°, the left arm is placed in front, and the right axilla is padded to widen the rib space on the operation side, which facilitates the exposure of the operation field.
(2) Incision Left posterior lateral thoracic incision, the incision should be bypassed 1 transverse finger below the inferior angle of the scapula to avoid pain caused by rubbing the surgical incision when the scapula moves after surgery. Through the fourth intercostal or resection of the fourth rib into the chest, so that the aortic isthmus arterial duct and pulmonary hilar are well exposed.
(3) Exploration of the arterial duct: After opening the chest, the left lung is pulled forward and downward, and the bulging part of the ductus arteriosus is seen in the ductal triangle formed by the pulmonary artery, vagus nerve and phrenic nerve. When the finger is probed in this triangle, continuous tremor can be found; after finger pressure on the ductus arteriosus triangle, the tremor of the main pulmonary artery disappears or is reduced.
(4) Incision of the mediastinal pleura: The mediastinal pleura is incised along the midline of the longitudinal axis of the descending aorta, up to the left subclavian artery and down to the pulmonary hilum. When separating the left subclavian artery, care should be taken not to injure the lymphatic vessels, and all suspicious ones should be ligated to avoid postoperative lymphatic leakage.
(5) Reveal the arterial duct: Separate the incised mediastinal pleura toward the pulmonary artery side to the pulmonary end of the arterial duct. 3~4 stitches of traction thread are sewn on the edge of the mediastinal pleura with a No. 4 silk thread, drawn and fixed on a sterile towel. At this point, the arterial catheter, aortic arch, left subclavian artery, pulmonary artery, vagus nerve and recurrent laryngeal nerve are clearly visible.
(6) Separate the catheter: Generally, the anterior wall of the catheter is first sharply separated with stripping scissors. Then separate the lower edge, carefully cut the ligamentous tissue above the catheter to reveal the upper edge of the catheter, separate the catheter along the upper edge upward, and finally use small right-angle forceps to extend the upper edge of the catheter along the posterior wall from below upward, then use right-angle forceps from above to gently expand the posterior wall gap of the catheter appropriately, and the catheter is completely free all around.
(7) Blocking test: Use small right-angle forceps to guide 2 heels of No. 10 wire, gently around the posterior wall of the arterial catheter, temporarily block the catheter, observe the heart rate and blood pressure, if there is a drop in blood pressure and tachycardia, the catheter needs to be closed carefully. Do not go too fast when ligating the wire through the posterior wall of the catheter to avoid damaging the posterior wall tissue of the catheter.
(8) Ligation of the catheter: Ask the anesthesiologist to lower the blood pressure to 70-80 mmHg systolic pressure, ligate the aortic end of the arterial catheter first, while touching the pulmonary artery side with a finger. Then ligate the pulmonary artery end. The ligature lines should be separated as much as possible to avoid overlapping, and the ligature should be applied evenly and slowly to prevent damage to the catheter wall and intima from excessive force.
(9) Suture the incision: suture the mediastinal pleura, stop bleeding thoroughly, count the instruments and gauze correctly, place a closed chest drain between the sixth ribs in the left axillary midline, ask the anesthesiologist to expand the lung and close the chest.
This procedure is most commonly used and is suitable for pediatric cases with long ducts and low pulmonary artery pressure.
2.The left lateral thoracotomy cut and suture surgical incision and exposure are the same as the unclosed arterial catheter ligation. After the catheter is sufficiently free to lower the pressure, the main and pulmonary artery ends of the catheter are clamped in parallel with two catheter forceps or Pott-Smith forceps, and the distance between the two forceps should be not less than 3~4mm to facilitate the cut and suture. The aortic side between the two clamps is sutured with 4-0 or 5-0 prolene sutures while cutting, usually with interrupted mattress sutures in the first layer and continuous sutures in the second layer. The pulmonary artery incision margin is then sutured. After the sutures are completed, the Pott-Smith clamp at the pulmonary artery end is opened first. If the eye of the needle is bleeding, the bleeding is stopped with hot gauze compression, and if it is still bleeding, the mattress suture is repaired, and then the Pott-Smith clamp at the aortic end is opened.
This procedure is suitable for cases where the catheter is thick, bleeding from intraoperative injury or infected and should not be ligated.
3.The left lateral thoracotomy clamp closure is performed by using a clamp closure device to nail in a metal tantalum nail of appropriate size to close the catheter. After the catheter is free, a thick wire is wound as a guide for placing the clamp closure device. The clamp is entered in the interstitial space between the main and pulmonary arteries, and the aortic end is clamped first, followed by the pulmonary end. Care should be taken to push the recurrent laryngeal nerve away to prevent it from being embedded in the clamp and causing injury.
This procedure is simple and effective.
4. Median sternotomy arterial catheter ligation is performed with a median sternotomy, a longitudinal incision of the pericardium, and the sternum is propped open. After the extracorporeal circulation is intubated, the assistants under the assisted circulation pull down the pulmonary artery trunk, reveal the distal pericardial reflex, cut the pericardium longitudinally, and look for and carefully separate the arterial conduit above the bifurcation of pulmonary artery. The aortic side is separated first, followed by the left pulmonary artery side, and then the end of the right-angle clamp is revealed on the ascending aorta side by using a right-angle clamp from the superior border of the left pulmonary artery, and guiding a double ligation by gently pulling out the 10 wire.
This procedure is suitable for intracardiac malformation combined with arteriovenous insufficiency.
5.Transpulmonary artery catheter closure under extracorporeal circulation After the establishment of extracorporeal circulation, the catheter is pressed with a finger or gauze ball, while cooling and reducing the flow, and the pulmonary artery is incised.
This procedure is suitable for adult patients, patients with severe pulmonary hypertension, or patients with preoperative leak.
Key points of intraoperative management.
(a) When opening the chest with a posterior lateral incision, the fourth intercostal space should be judged accurately so that the arterial conduit is well exposed.
(2) Pay attention to the protection of the recurrent laryngeal nerve when separating and especially cutting the arterial catheter.
(c) If bleeding is encountered during the separation of the catheter, the first measure should be to stop the bleeding with finger pressure. Small mediastinal vessels bleeding can be stopped by compression. If compression does not stop bleeding, close observation of the descending pressure can be used to clarify the bleeding site and select the appropriate measures to deal with it, in order to clamp the aorta above and below the arterial catheter for suturing. Do not use hemostatic forceps at will, so as not to increase the rupture and bring more serious consequences.
(D) When ligating the arterial catheter, the force should be smooth to interrupt the blood flow traffic. Excessive ligature force may result in cutting, and too loose may result in residual shunt.
(e) When ligating large catheters via intrapericardial separation under extracorporeal circulation, offstage personnel should feel the arterial pulsation of the lower extremity. If the arterial pulsation of the lower extremity disappears, the blood pressure of the upper extremity increases, and the lower extremity becomes pale and anuric after ligation, it indicates that the descending aorta may be ligated by mistake and must be loosened immediately.
Postoperative complications.
(a) Hemorrhage is mostly seen in cases of coarse catheters with pulmonary hypertension, and occurs during freeing, ligation, clamp closure or dissection, and is often related to the operator’s unskilled and inexperienced technique. Hemorrhage caused by rupture of the catheter tissue or the main or pulmonary artery end of the catheter can be fatal immediately if not controlled in a timely manner. Therefore, the operator must be familiar with the local anatomy, and the operation of separating the catheter should be cautious, gentle and meticulous, and the action of the clamp should not be too large. When ligating, slow force is appropriate, do not pull the catheter, so as not to cut or pull off, resulting in serious consequences. Once bleeding occurs, do not blindly clamp and pull, but immediately press the bleeding site with your fingers. In the case of adequate blood supply, good lighting conditions and unobstructed suction duct, expose the local area, see the bleeding site and bleeding rate, block the main and pulmonary arteries at both ends of the catheter and suture to stop the bleeding. If the above surgical operation is not possible, after blocking the aorta, the pericardium can be incised in front of the left phrenic nerve, and the pulmonary artery can be clamped inside the pericardium and its blood flow to the catheter can be blocked. Or establish extracorporeal circulation to repair the rupture under deep hypothermic low-flow or deep hypothermic stop circulation.
The preventive measures are to clarify the local anatomical relationship, pay attention to protection during operation, make less unnecessary separation, and leave a layer of fibrous connective tissue on the surface of the recurrent laryngeal nerve, which can significantly reduce the chance of injury.
(c) Acute left heart failure often occurs after blocking the catheter, the patient’s heart rate increases, foamy sputum or bloody secretions are aspirated from the tracheal intubation, and the lung is heard to be woven H绮患 笆贝恚蚧嵋鹧瓜陆怠 (12) Mu moisture С5任O蟆7乐勾胧┦窃悄瓒系脊芮敖笛梗剝剝咧鸾プ瓒系脊不壞 ┓ (5)笮乃ソ哒飨螅τ啃摹 ⒈ Vち己玫耐事С价值观但胧 (d) Arrhythmia during induction of anesthesia Most often seen in pediatric cases with larger catheters or those with combined intracardiac malformations. Common arrhythmias include supraventricular tachycardia, premature ventricular contractions, and severe ventricular arrhythmias. Close cardiac monitoring and appropriate management are important.
(v) Postoperative hypertension is mostly seen after closure of the coarse catheter. Sodium nitroprusside pumping is commonly used to lower the blood pressure. Sedative and diuretic drugs are given when necessary to prevent and treat cerebral complications.
(f) Pulmonary complications commonly include pulmonary atelectasis, pneumothorax, hemothorax and pneumonia, manifesting as shortness of breath and decreased breath sounds on the affected side. In addition, patients with coarctation with pulmonary hypertension can be given several hours of postoperative respiratory support, enhanced respiratory physiotherapy and aggressive anti-inflammatory therapy, and most can be spared such complications.
The surgical treatment of patent ductus arteriosus is one of the safer and more effective forms of congenital heart disease. The key to successful surgery lies in the selection of the appropriate surgical approach according to the characteristics of patent ductus arteriosus, skilled and delicate surgical techniques, and good cooperation between anesthesiologists and perfusionists.