Ventricular septal defect refers to the embryonic underdevelopment of the ventricular septum, which forms abnormal traffic and produces a left-to-right shunt at the ventricular level; it can exist alone or as a component of some complex cardiac malformation. Ventricular defects are the most common form of congenital heart disease. Ventricular septal defects account for approximately 20% of all congenital heart disease and can exist alone or in conjunction with other malformations. The defects range from 0.1-3 cm, larger in the membranous region and smaller in the muscular region, which is also known as Roger’s disease. If the defect is <0.5 cm, the flow is small and there are no clinical symptoms. In small defects, the right ventricle is predominantly enlarged, while in large defects, the left ventricle is more enlarged than the right ventricle.
According to the location of the defect, it can be divided into five types.
1, supraventricular crest defect: located in the right ventricular outflow tract, above the supraventricular crest and below the main and pulmonary valves, and in a few cases combined with main and pulmonary valve closure insufficiency.
2, subventricular crest defect: located in the septal membrane, this type is the most common, accounting for about 60-70%.
3, posterior septal defect: located in the right ventricular inflow tract, posterior to the tricuspid septal valve, accounting for about 20%.
4, myocardial defect: located in the apical part, for myocardial trabecular defect, systolic time septal myocardial contraction makes the defect smaller, so the left to right shunt flow is small.
5.Common ventricle: Both the membrane and myocardial parts of the septum are undeveloped, or multiple defects, which are less common.
A septal defect means that there is a defect in the septum that separates the right and left ventricles (the two lower chambers of the heart). This heart defect causes oxygen-rich blood from the left ventricle to flow into the right ventricle instead of the normal flow into the aorta. Ventricular septal defects (VSDs) result in the mixing of oxygen-rich blood from the left ventricle with oxygen-deficient blood from the right ventricle.VSDs also vary in size. Smaller VSDs cause no problems and may even close on their own. Larger VSDs, on the other hand, can cause not only an overload on the left ventricle, but also excessive blood pressure in the right side of the heart and lungs due to too much blood in the right ventricle, which in turn leads to high blood pressure. This can increase the workload of the heart, which can lead to heart failure and cardiac dysplasia. If the VSD is not closed at this time, it can lead to damage to the delicate pulmonary arteries, creating what is called pulmonary hypertension. This is when happy surgery is needed to repair the VSD.
The pathophysiological effects of ventricular septal defects are mainly due to the communication between the right and left ventricles, causing blood shunts and the resulting series of secondary changes. The amount and direction of shunt flow depends on the size of the defect caliber and the pressure step difference between the right and left ventricles, which in turn depends on the compliance of the right ventricle and the condition of the pulmonary circulatory resistance.
Under normal pulmonary and body circulatory resistance, the systolic pressure in the left ventricle is significantly higher than that in the right ventricle, with a ratio of approximately four to one. With a ventricular septal defect, a left-to-right shunt of blood is generated through the defect whenever the ventricle is in systole. In the first few weeks of life, the left-to-right shunt is low because the small pulmonary arteries remain somewhat embryonic and pulmonary vascular resistance is still high; thereafter, the shunt gradually increases. As the pulmonary blood flow increases, the pressure in the pulmonary veins and left atrium also increases, resulting in increased fluid in the interstitial space of the lung, decreased compliance of the lung tissue, impaired pulmonary function, and susceptibility to respiratory infections. As a result, respiratory distress can occur with increased fractional flow, especially in infants and children. Respiratory distress increases energy expenditure, with a corresponding decrease in blood flow in the circulation, thus affecting systemic development. The left-to-right shunt at the ventricular level increases the load on both the left and right ventricles. Initially, as pulmonary blood flow increases, the total pulmonary resistance is regulated accordingly, so that the increase in pulmonary artery pressure is not significant (when the pulmonary vascular bed is normal, pulmonary blood flow increases fourfold, but the total pulmonary resistance can still be regulated by itself without significant changes in pulmonary artery pressure). Subsequently, small pulmonary arteries undergo spasm, contraction and other reactive changes, and pulmonary vascular resistance increases, and pulmonary artery pressure rises accordingly, while pulmonary venous and left atrial pressure decreases, and interstitial pulmonary edema and lung tissue compliance improve accordingly, and respiratory function and respiratory infections improve. Despite this relative balance and remission phase, the small pulmonary arteries gradually develop from functional changes such as spasm to organic changes such as muscle hypertrophy, intimal thickening, wall fibrosis and lumen thinning, resulting in increasing pulmonary artery resistance and severe pulmonary hypertension. With the above pathophysiological evolution, the left mid-body shunt flow develops from a gradual decrease to a bidirectional shunt, and eventually forms a right-to-left reverse (reverse) shunt, the latter of which reduces the oxygen content of the arterial blood in the body circulation, resulting in cyanosis of the lips and fingers and toes, especially during physical activity, which is known as Eisenmenger syndrome. At this point, the left ventricular load is reduced, while the right ventricular load is further increased. The length of the pathophysiologic evolution described above varies depending on the size of the defect. In large-bore defects, severe pulmonary hypertension may appear by the age of 2 to 3 years; in moderately large defects, it may extend to about 10 years of age, whereas in small-bore defects, the above-mentioned development is slower and may appear only in adulthood, and occasionally it is seen that the patient passes through life unharmed.
Statistically, about 20% of small-bore defects can close on their own in early childhood. Epidemiological surveys show that the prevalence of ventricular septal defects in infants and children is about 0.3%, while according to the adult firm, the prevalence of ventricular septal defects in adults is 0.03%, which can fully prove the fact of self-closing. In contrast, patients with large ventricular septal defects and combined with severe pulmonary hypertension, if not treated surgically, have a significantly shorter life span after the development of Eisenmenger syndrome, with an average life expectancy of 25 to 30 years.
A left-to-right shunt is generated at the ventricular level, and the amount of shunt flow depends on the size of the defect. In large defects, the blood flow in the pulmonary circulation increases significantly, and after flowing into the left atrium and ventricle, it flows back into the right ventricle at the ventricular level through the defect and enters the pulmonary circulation, thus increasing the load on the left and right ventricles, increasing the size of the left and right ventricles, increasing the blood flow in the pulmonary circulation leading to an increase in pulmonary artery pressure and an increase in the systolic load on the right ventricle, and eventually entering the phase of obstructive pulmonary hypertension, which can occur in both directions or with a right-to-left shunt.
Symptoms
Small defects may be asymptomatic. In large defects, symptoms appear early and are so pronounced that they affect development. There are palpitations and shortness of breath, weakness and susceptibility to lung infection. In severe cases, heart failure may occur. Cyanosis may occur in cases of significant pulmonary hypertension, and the disease may predispose to infective endocarditis.
Physical signs
The typical sign is a rough systolic murmur of grade 4-5 between ribs III-IV at the left sternal border, which is conducted to the precordial region, accompanied by a fine systolic tremor. If the fractional flow is high, there may be a functional diastolic murmur in the apical region. The second pulmonary valve sound is hyperactive and split. In severe pulmonary hypertension, there is a diastolic murmur of relative pulmonary valve insufficiency in the pulmonary valve region, and the systolic murmur of the original septal defect may be diminished or absent.
Clinical manifestations
According to statistics, about 20% of small-bore defects can close on their own in early childhood. Epidemiological surveys have shown that the prevalence of ventricular septal defect in infants and children is about 0.3%, while according to the adult firm, the prevalence of ventricular septal defect in adults is 0.03%, which can fully prove the fact of self-closing. The average life expectancy of ventricular septal defect without surgical treatment is 25-30 years, and the life span is significantly shortened after the appearance of Eisenmenger syndrome.
Smaller defects with less fractional flow are usually asymptomatic. Those with larger defects and higher fractional flow may have developmental disorders, palpitations and shortness of breath after activity, recurrent pulmonary infections, and in severe cases, symptoms such as respiratory distress and left heart failure. When mild to moderate pulmonary hypertension is present, with a corresponding decrease in left-to-right shunt flow, pulmonary infections and other conditions may be reduced, but symptoms such as palpitations, shortness of breath, and limitation of activity may remain or become more pronounced. In severe pulmonary hypertension with bidirectional or reverse (right-to-left) shunts, cyanosis, known as Eisenmenger’s syndrome, is seen and worsens with physical activity and pulmonary infections. Eventually, right heart failure occurs.
On physical examination, those with larger caliber defects are generally less developed and thinner. In advanced cases, cyanosis of lips and fingers is seen, and in severe cases, there may be a thousand fingers (toes), as well as right heart failure manifestations such as hepatomegaly and swelling of the lower limbs. In patients with higher flow rates, an increased pulsation in the precordial region, an anterior bulge of the chest wall, and an enlarged turbinate on percussion can be seen.
Cardiac auscultation: Grade III-IV full systolic jet murmur can be heard between the 3rd and 4th ribs at the left border of the sternum (depending on the location of the defect), and tremor can be felt at the same location. In cases of elevated pulmonary artery pressure, a hyperactive 2nd tone may be heard in the pulmonary valve area. Sometimes the surface of the defect is covered by tendons, papillary muscles or abnormal membranous material, resulting in a weaker murmur and less pronounced tremor, but the nature of the ejection murmur can still be judged. In cases of high fractional flow, a diastolic rumbling murmur can still be heard in the apical region due to increased blood flow through the mitral valve orifice. In severe pulmonary hypertension with similar right and left ventricular pressures, the systolic murmur decreases or disappears and is replaced by a loud second heart sound in the pulmonary valve area or a diastolic murmur with incomplete pulmonary valve closure (Graham Steell murmur). In high ventricular septal defect with aortic valve prolapse and incomplete closure, in addition to the systolic murmur, a decreasing diastolic murmur with apical conduction can be heard, which can be easily mistaken for a sustained murmur due to the short interval between the two murmurs.
Diagnostic tests
X-ray examination
The heart shadow is mildly to moderately enlarged, the left heart edge is prolonged to the left and downward, the pulmonary artery cone is bulging, the aortic
The pulmonary artery cone is enlarged, the aortic node is small, and the pulmonary hilum is congested. In severe obstructive pulmonary hypertension, the enlargement of the heart shadow is not significant, the right pulmonary artery is thick, the distal protrusion is small, the branches are rattle-like, and the peri-pulmonary field texture is sparse.
Cardiac examination
There is often a mild elevation in the precordial region. Systolic tremor can be felt between the 3rd and 4th ribs at the left edge of the sternum, and a grade III-IV all-systolic murmur can be heard; in the case of a high funnel defect, the tremor and murmur are located in the 2nd intercostal region. The second tone in the pulmonary valve area is hyperactive. In high fractional flow, a soft functional mid-diastolic murmur can still be heard in the apical region. In cases of reduced fractional flow due to pulmonary hypertension, the systolic murmur gradually decreases or even disappears, whereas the second tone in the pulmonary valve area is markedly hyperactive, split, and may be accompanied by a diastolic murmur with incomplete pulmonary valve closure.
Electrocardiographic examination
Small defects show normal or left-sided electrical axis. In larger defects, left ventricular hypervoltage and hypertrophy or right and left ventricular hypertrophy are seen with increased fractional flow and pulmonary artery pressure. In severe pulmonary hypertension, it shows right heart hypertrophy or with strain. I. X-ray: The heart shadow is mostly unchanged in small defects. When the defect is moderately large, the heart shadow has different degrees of enlargement, with the right ventricle predominant. In large defects, both the left and right ventricles are enlarged, the pulmonary artery trunk is protruding, the pulmonary vascular shadow is enhanced, and in severe pulmonary hypertension, the lateral band of the lung field is clear instead.
Echocardiography
The left atrium, left and right ventricular internal diameters are enlarged, and there is continuous interruption of septal echo. Doppler ultrasound: maximum turbulence can be deeply measured by tracing from the defective right ventricular surface to the defective orifice and left ventricular surface.
Cardiac catheterization
The oxygen level at the right ventricular level is more than 0.9% of the volume of the right atrium, and occasionally the catheter can reach the left ventricle through the defect. Depending on the amount of fractional flow, there is a variable increase in pulmonary artery or right ventricular pressure.
Treatment options
Internal treatment
The main treatment is to prevent and treat infective endocarditis, pulmonary infections and heart failure.
Surgical treatment
If the defect is small and the X-ray and electrocardiogram are normal, surgery is not necessary. If there is/ or there is no pulmonary hypertension, surgery is best if the left-to-right shunt is predominant, preferably at the age of 4-10 years. The surgery is not recommended for those who have a predominantly right-to-left shunt.
Surgical principles
(1) In view of the possibility of natural closure of ventricular defects, children with small defects and young age can be observed until 2-3 years of age.
(2) Very small ventricular defect, asymptomatic, chest X-ray and ECG are normal, generally do not need surgical treatment. However, regular outpatient follow-up should be performed.
(3) For children with ventricular defect with no possibility of self-healing and no pulmonary hypertension, elective surgery can be performed at the age of 1~4 years. The main method of surgery: interventional treatment or intracardiac direct view ventricular defect repair under medium and low temperature extracorporeal circulation can be used.
(4) The funicular defect, especially the bicuspid subvalvular defect, should be radically treated before the age of 2 years heart to prevent the occurrence of aortic valve prolapse.
(5) Some large ventricular defects, recurrent pneumonia, heart failure, unsatisfactory control by active medical treatment, regardless of age and weight restrictions, should be treated by early surgery. If the technical and equipment conditions are inadequate, pulmonary artery circumferential reduction can be performed first to relieve the symptoms. Radical surgery should be performed after 3-6 months.
(6) Children with severe resistance pulmonary hypertension and clinical cyanosis should be contraindicated for surgery.
(7) For more details on the interventional treatment of ventricular defects, please refer to Section 4, Interventional Treatment of Premature Heart Disease.
(8) Regular postoperative follow-up should be carried out to pay attention to the presence of residual shunts and the recovery of cardiac function.
1. Indications for surgery
In large ventricular septal defects, 25%-50% die within 1 year of age due to pneumonia and heart failure. Therefore, infants with recurrent heart failure should be treated with defect repair. About half of the small defects may close on their own, except for complications of bacterial endocarditis, which can be observed until 10 years of age before considering surgical treatment. Very small defects may not require surgery for life. Infants and children with a fractional flow of more than 50% or with increased pulmonary artery pressure should be operated early to prevent a continuous rise in pulmonary hypertension. If severe obstructive pulmonary hypertension has been achieved, it is a counter indication for surgery.
2.Surgical method
Under general anesthesia with tracheal intubation, a median sternotomy is performed to establish extracorporeal circulation. After blocking the cardiac circulation, the anterior wall of the right ventricular outflow tract is incised, which can reveal various types of ventricular septal defects, but there is some damage to the myocardium. The right heart function is affected and the right bundle branch is damaged. Currently, the trans-right atriotomy route is used, which is better for revealing membrane defects. For higher defects, the transpulmonary route is preferred. Smaller defects with fibrous tissue at the edges can be sutured directly, while those with defects >lcm can be patched with polyester woven sutures. The conduction bundle goes through the lower edge of the membranous defect, and the septal posterior defect is easily mended by sutures, which should be avoided and sutured against the root of the septum.
With the increasing safety of cardiovascular surgery and the increasing attention to the aesthetics of the intraoperative trauma incision, minimally invasive small incision surgery has been gradually favored by the majority of aesthetic patients in recent years. The following is a brief introduction of related knowledge.
(1) Conventional incisions
1.Median sternal incision, skin incision is located in the middle of the anterior chest, about 20-25cm long, and all the sternum will be split, easy to liquefy or infect the incision after surgery, poor wound healing, easy to leave knife scars and deformities such as chicken chest.
2.Left posterior lateral thoracic incision, this incision usually starts from the midpoint of the spinous process and the posterior border of the scapula, and then goes forward around the subscapular angle for 2cm, and continues forward to the anterior axillary line, about 15-20cm long incision, which is traumatic and has obvious postoperative wound pain, and part of the postoperative incision is easily liquefied or infected to affect the healing.
(2) Small incision
Minimally invasive small incision refers to the incision length of 6~10cm, and the incision is located in the relatively hidden part of the chest.
1.Small right chest incision
Small right axillary incision: 5-9 cm incision is made at the second rib intersection of the right mid-axillary line and the fifth intercostal intersection of the anterior axillary line, and the length depends on the age and height.
It is generally used for children under 15 years old, and the thoracic cavity is relatively small in children. The rib cage is flexible, so it is safe to perform some simple congenital heart malformations, such as the repair of atrial septal defect and ventricular septal defect. We can also perform surgery for triple atrial heart, pulmonary vein ectopic drainage, mitral valve insufficiency repair and valve replacement.
This incision should not be used for children with severe pulmonary hypertension with pulmonary dysplasia or pulmonary infection and severe pulmonary hypertension at birth <4 months, complex congenital heart malformations such as very poor pulmonary vascular development in tetralogy of Fallot, or children with unclear preoperative diagnosis. < p="">
Right anterolateral incision: An arcuate incision is made from the axilla to the 5th rib in the midclavicular line, approximately 8 to 12 cm long, and in women, a skin incision is made along the inferior border of the breast, along the anterior serratus and pectoralis major muscles, and into the chest through the 3rd or 4th intercostal space.
The indications are the same as before. In adults, the thorax is larger, less elastic, and the operative field is deeper, so the anterolateral incision is generally preferred.
2.Small left axillary incision, the specific site is the same as the small right axillary incision, except that it is located on the left side and is used for the surgical treatment of patent ductus arteriosus, after complete hemostasis, no chest drain can be placed, which greatly reduces the postoperative pain of patients.
3.Small incision of the lower sternum
The skin incision is located in the lower middle 1/2 of the sternum to the subxiphoid process, the incision is about 7-10cm long, splitting the lower middle 1/2 to 2/3 of the sternum, and can be extended upward to open the chest if necessary if it is difficult to reveal, which is relatively safe. The incision has small trauma, less bleeding, and the stability of the thorax is not completely destroyed, which is conducive to the recovery of respiratory function after surgery.
The small lower sternal incision is suitable for the repair of atrial septal defect and ventricular septal defect. It is also able to perform surgery for triple atrial heart, pulmonary vein ectopic drainage, mitral valve closure insufficiency repair and valve replacement.
In conclusion, the characteristics of small incision surgery are beautiful incision, addiction, small trauma, less bleeding, fast recovery, good healing, less deformity, less cost, etc.; however, for patients with complicated conditions, or adults with obesity and flat chest, they must be carefully selected according to their conditions and doctors’ opinions.
(3) Minimally invasive ventricular defect repair under complete thoracoscopy
Introduction: TV thoracoscopic cardiac surgery is considered to be another major technological revolution in the field of cardiac surgery since the introduction of extracorporeal circulation, and is a representative procedure of modern minimally invasive cardiac surgery. Compared with traditional surgery, thoracoscopic minimally invasive cardiac surgery has the following advantages: small skin incision (1-2cm), no cutting of muscles, no bone damage, small trauma and fast recovery, light post-operative pain, discharge from hospital in 5-7 days, meeting cosmetic requirements, and lower cost than traditional cardiac surgery.
Indications for surgery: various types are ventricular septal defect, age greater than 3 years, weight more than 30 pounds, ventricular defect with aortic valve closure insufficiency should be operated in time, those with pulmonary valve stenosis or outflow tract stenosis ventricular defect is mostly larger, those with pulmonary artery pressure/aortic pressure <0.75 can be operated, etc. < p="">
Contraindications to surgery: Pulmonary artery pressure/aortic pressure >0.90 contraindicates surgery
The procedure: The thoracoscopic incision is made in the right chest, with three small incisions of about 2 centimeters, without cutting the muscles and without cutting the bones. Similarly, the surgeon first circulates the blood in the body around the heart using a tube that is inserted in the groin (femoral artery and femoral vein diversion). During the operation, a stopping fluid is injected into the heart to stop it from beating, and the body’s blood is passed through an extracorporeal circulation machine to receive oxygen and constant circulation. During the operation, the surgeon cuts open the heart to correct the heart deformity. At the end of the surgery, the heart is re-sutured closed and she is restored to beating. The extracorporeal circulation machine is evacuated, the tubes are removed, and the incision is closed.
Postoperative management
①For those who have obvious pulmonary hypertension before surgery, it is advisable to apply the respirator continuously until the next morning after surgery. If the respirator cannot be removed 48 hours after surgery, tracheotomy should be done instead of endotracheal intubation.
②Pulmonary hypertension patients often have postoperative circulatory instability and need to maintain blood pressure with positive inotropic drugs.
In some cases, the conduction bundle is transiently damaged, and the conduction function will be restored automatically within a few days.
Surgical outcome
① depends on the severity of the patient’s disease, the early stage of the disease, and the degree of perfection of the operation and the appropriateness of the postoperative treatment. In patients without significant pulmonary hypertension, the operative mortality rate is within 2%.
②In patients with severe secondary pulmonary vascular lesions before surgery, the incidence of respiratory and circulatory complications after surgery is high, and the mortality rate is also significantly higher. Recovery depends on the extent of their pulmonary vascular lesions, and the prognosis is poor if the lesions have become irreversible.
Complications
Infective endocarditis is rare in infants under 1 year of age, and the highest incidence was seen in a group of patients by Corone et al. between 15 and 29 years of age. In general, the longer the survival time, the greater the chance of complicating infective endocarditis. According to the literature, the incidence is 25-40%. However, since the widespread use of antibiotics and chemotherapy, the incidence has decreased significantly, from about 5-6% to as low as 2-3.7%. However, the annual incidence is still 0.15% to 0.3% of patients.
Aortic valve insufficiency
Nodas reported a 4.6% incidence and Tatsuno reported an 8.2% incidence. The causes of insufficiency of closure are twofold.
(1) The defect is located immediately inferior to the aortic annulus, which lacks adequate support. When a high velocity shunt is ejected from left to right, it pulls the aortic valve leaflet downward, first lengthening it and then creating a prolapse, resulting in incomplete closure. If the defect is not repaired in time, the insufficiency of closure will gradually worsen.
②Some defect edges thicken, mechanically contract, and even form fibrous bands that pull on the aortic valve, producing incomplete closure.
Conduction block
Secondary fibrosis of the endocardium at the edge of the membranous defect compresses the adjacent conduction bundle, producing complete or incomplete conduction block.