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Atrial septal defect
Incidence
Atrial septal defect is a congenital heart disease the most common lesions. According to Abbott 1000 autopsy cases of simple congenital heart disease, atrial septal defect in the first place, accounting for 37.4%. But no obvious clinical manifestations, often overlooked, and thus the clinical incidence is lower than the above figures. In 1982, Huang Ming-new 4043 cases in Shanghai and other statistics congenital heart disease, of which 1,054 cases of atrial septal defect, accounting for 26.1%, congenital heart disease in the first place. Renji Hospital, Shanghai Second Medical University, 7745 cases of open heart surgery, a total of 693 cases of atrial septal defect, accounting for 8.9%.
Multiple atrial septal defects in women, and men incidence ratio of about 2:1. However, the and other surgical cases, men are more to female ratio of about 1.7:
Embryology and pathogenesis
In the first 4 weeks of embryonic primitive heart chamber began to separate into four atrioventricular cavity. Development process: the original heart of the central cavity front and both sides of the outstanding growth of inward thickening, the formation of endocardial cushion. Front and two endocardial cushion gradually close to each other in the midline fusion of the both sides of the organization is part of the composition of the formation of atrioventricular valves in the right compartment for the tricuspid valve; the left side of the large mitral valv


e. In addition, the side of the pad has developed into a valve, a common component tricuspid and mitral valves, the atria and ventricles separated. Meanwhile, the atria and ventricles are also the two ends of the interval from the midline to the growth of endocardial cushions, will be separated into two chambers of the heart atria and two ventricles.
After the interval from the atrial wall of the center line on the beginning of the growth of the endocardial cushion, crescent-shaped lower edge, and finally, and endocardial cushion fusion, known as the primary atrial septum, the atrial separated into left and right are two cavities (Fig. 33 a 01).
If the process of development, stop the growth of the primary atrial septum, not with left endocardial cushion fusion and space, that is a primary hole (or the first hole) defects. In the primary defect cases, often even the endocardial cushions of atrioventricular valve hypoplasia phenomena, such as mitral valve and tricuspid valve septal leaflet largest division, and the abdomen was divided vest endocardial cushion fusion and Wo, called atrioventricular canal. Sometimes both ventricular septal defect (see chapter II).When the primary atrial septum and down the growth but not yet integrated before endocardial cushion, the upper gradually be absorbed to form both sides of the atrium of the new channel, called the atrial septum secundum. Hole formed in the secondary, while, at the right side of the primary atrial septum, while the secondary atrial septum appears, the lower edge of the crescent-shaped openings are not on the endocardial cushion, but bias after the bottom of the downward vena cava entrance growth.
In order to maintain the blood circulation of fetal left heart, the lower edge of the secondary atrial septum and atrial septal primary between the upper edge though, but not integration. As the primary septum valve (valve of foramen ovale). Only allow the blood flow from right to left turn, and to prevent the reflux from left to right (Fig. 33 - 02). Secondary atrial septal defect left oval, known as the foramen ovale.After birth, start breathing, pulmonary circulation of the blood volume has increased considerably, but the left ventricular muscle thickness and there is still the equal development. With the growth of the baby, more than pulmonary aortic valve, the left began as one room muscle hyperplasia, hypertrophy, pressure gradually increases, the discharge of the left atrium the blood. Thereby left atrial pressure too in the right atrium, foramen ovale valve close to the secondary atrial septum to close the foramen ovale. Usually in August or longer, completely cut off left and right heart blood supply room. However, 20% to 25% of the normal, foramen ovale valve and atrial septal not all fusion, the size of the hole left by the probe, known as patent foramen ovale. The existence of such a hole does not cause blood shunt, there is no clinical significance. However, implementation of cardiac catheterization examination, cardiac catheterization may occasionally enter the left atrium through the foramen ovale, which should be worth noting that, in order to avoid confusion with the atrial septal defect.
If the primary atrial septum is absorbed too much, or developmental disorders secondary to atrial septum, the two edges can not touch the bottom, and the remaining gap, the formation of secondary hole (or the second hole) defects, which is a common clinical practice. Sometimes the primary and secondary hole hole defect may exist.
Categories
Classification more consistent with the scholars is not intended to pan. and based on embryology and pathological anatomy, is divided into two categories, namely primary and secondary bore hole defect defect, which is more common than the former. According to the Shanghai Chest Hospital, Fu Wai Hospital, Chinese Medicine, Shanghai Second Medical University and the PLA Fourth Military Medical University Hospital and other units of information: (including internal information), the end of 1989 from a total of 1957 implementation of the atrial septal defect 2970 cases of surgery, which accounted for 95.7% of secundum defect (Table 33-0I). Clinical manifestations and treatment of the different sub-sections will be described.Autopsy
Secundum defect number, size, shape and position are different. Most of the defects for the solitary. Can sometimes have two or many holes exist. A few of the total large atrial septal defect, can accommodate a small probe. General; even if they can live to adulthood cases, defects is not small, diameter about 2 ~ 4cm. The shape and location of defects are often associated with type.The most common clinical type, the total incidence of 75% or more. Vast majority of cases. Onset of a single defect, oval-shaped, about 2 ~ 4cm, located in the coronary sinus after the above. Good around the edges, especially the upper part is more obvious (Figure 33-03). Far from the conduction system defects, easy to suture, the effect is good points. However, individual cases of defect, was shaped sieve.(B), the low-defect cavity or said
Oval hole than rare, accounting for 12% or more. Defects in a single onset, location, low, oval-shaped, lower edge of the absence, and the entrance of the inferior vena cava no obvious boundaries (Figure 33-04). Sometimes accompanied by the inferior vena cava valve, surgery should be special attention.
(C) said high on the cavity or defect
Also known as venous sinus (sinus venosus) defects, there are many case reports of foreign, domestic rare, accounting for 3.5% or more. Defects in the oval hole at the top, superior vena cava close to the population. Defects generally small, about 1.5 ~ 1.75cm, the lower edge of the crescent for the apparent atrial septal, absence of upper bounds, and the superior vena cava often connected, so that blood flow to the left superior vena cava and right atrium (Figure 33 -05). Almost all of these cases, right upper or right middle lobe associated with anomalous pulmonary venous blood flow back into the superior vena cava.
(D) mixed type or both of the two above said defects
Clinically rare.
Cases of secundum defect patients, sometimes accompanied by other abnormalities, such as pulmonary stenosis, right pulmonary venous return, mitral stenosis (Lutembacher syndrome), double superior vena cava, right aortic arch, etc., accounting for about 15% .
Pathophysiology
Normal, the left atrial pressure (8 ~ 10mmHg) than either systolic or diastolic high right atrium (3 ~ 5mmHg) o Therefore, when the septal defect is present, the blood line from left to right shunt, there is no clinical symptoms of cyanosis . How many sub-flows with the defect size and left the room right heart pressure gradient directly proportional to the level and pulmonary vascular resistance is inversely proportional. Generally up to 7 ~ 20L per minute range (normal right heart flow of about 5L), over the whole body circulation rate 2 to 3 times, or even 4 times. The amount of general circulation has little effect on the whole body, blood pressure changes very little.
As the result of cardiac shunt through the right atrium and right ventricle and pulmonary blood flow to the heart is more than the left and right atrium and right ventricle and main pulmonary artery in which to expand, is a typical type of diastolic overloading; left atrium , the corresponding left ventricular and aortic narrowing.
With age, pulmonary artery spasm, and then gradually produce intimal hyperplasia and thickening middle, a narrow lumen and resistance caused by increased formation of pulmonary hypertension and reduce the sub-flow. In 1961, Besterman report the status of pulmonary hypertension in two Sui: dynamic pressure, pulmonary blood circulation is the result of increased pulmonary arterial resistance is not, within the 5 wood/m2; obstructive pulmonary hypertension, is the lung Small artery disease, the result of increased resistance, the resistance 5 wood/m2 West, the former is more common, the latter only 15% to 18%. Pulmonary hypertension, not only can often lead to pulmonary complications such as respiratory infections and thrombosis, and enables the output of the right heart blood impeded, resulting in right ventricular and right atrial hypertrophy, and finally lead to right heart failure. But the burden of high right heart blood with physiological functions, so the age of the general failure occurred later, mostly in 20 to 30 years of age.
When the right ventricular pressure increased to a certain limit, the right atrium and the reversible part of the blood flow into the left atrium, the formation from right to left shunt, cyanosis produce clinical symptoms. This shows that the evolution into the late stage of disease.More symptoms of ASD are inconsistent with the defect size and number of closely related sub-flow. Defect is greater, the earlier onset of symptoms; defects were small, long-term no symptoms, has been sneaking up to old age. Most cases have no symptoms in the pediatric period, often before they were found on physical examination; the general to the adolescence, the majority in the 21 to 40 years old symptoms began to appear.
The main symptoms of labor, shortness of breath, palpitations or respiratory tract infection and heart failure.
Case because the baby after birth, pulmonary vascular resistance is still high, it is a huge defect, could have a small amount of blood from right to left shunt, and a few months after a mild, decreased pulmonary vascular resistance, right atrial pressure is also lower than the left atrium, cyanosis The more lines disappear because of the sub-system from left to right shunt of blood's sake. But by the late course of the blood into upstream (from right to left), then a certain degree of cyanosis, and continue to increase until death.
Pediatric patients because of pulmonary congestion, is a recurring severe lung infection, manifested as more cough, shortness of breath, and even symptoms of pneumonia. As efforts Liuliang the reduction of the left, most patients have the energy deficiency, easy weary and breathing difficulties. Labor was short of breath and heart palpitations after more. In addition, long-term right ventricular diastolic overload exists, may be secondary to pulmonary hypertension and right heart failure. But its evolution is relatively slow, can be persistent for several years.
(B) signs
Most of the normal body growth. Right ventricular enlargement, with age, can make close to the sternum and left rib contours show bulging full. Palpation can be found lifting of the pump power increased. Percussion, the heart of community can be expanded, especially in the first 2,3-intercostal left chest expansion is more obvious due to pulmonary artery.
Cardiac auscultation, the main findings of systolic murmur for the pulmonary valve area and a second tone hyperthyroidism and division; the diagnosis is important. Systolic murmur usually appears later, more than 3 to 4 years old before they can hear. The loudness of noise, mostly grade ~ , showing ejection to the left of the first intercostal space near the sternal edge 2,3 is the most loud, sometimes accompanied by tremor. The systolic murmur was not produced by blood flow through the defect, but because of the large amount of blood through the normal pulmonary valve and into the pulmonary artery caused by expansion. Hyperthyroidism and pulmonary second sound split, but also because a lot of right ventricular blood into the pulmonary artery, pulmonary valve closed so that a strong, slightly later formed. Part of a larger defect cases can be heard before the area in mind the relative tricuspid stenosis with a short diastolic murmur drum samples, the Department of a large number of blood into the right ventricle through the tricuspid valve port j in some cases, arising in the left sternal border systolic murmur heard the first 4,5 intercostal enhance or diastolic murmur heard the former is caused by the enlarged right ventricle relative tricuspid insufficiency produced, while the latter but the relative pulmonary valve regurgitation caused the accident. When after the formation of pulmonary hypertension; pulmonary valve area can be seen to reduce systolic murmur, but the second sounds more obvious hyperthyroidism, and separatist narrowed or disappeared.
Advanced cases, right heart failure occurs when there are jugular vein engorgement, hepatic Japan hypostatic edema and other signs.
(C) Radiographic
Radiological signs mainly as follows: enlargement of the heart, particularly the right atrium and right ventricle most obvious, which in the right anterior oblique photos. Is more clear; prominent pulmonary artery segment; hilar shadow by deep lung field congestion, sometimes seen under the perspective of hilar dance, advanced cases may have calcification; narrow aortic arch (Figure 33-06). In addition, the general case there is no left ventricular dilatation, with ventricular septal defect or patent ductus arteriosus difference.
(D) ECG
A typical ASD often show increased P wave, right axis deviation, often 60 to 180 degrees. Most cases may have incomplete or complete right bundle branch block and right ventricular hypertrophy, pulmonary hypertension associated with right ventricular strain may have. The amount of face-centered vector icon clockwise QRS loop was shifted, the Department is located in the main ring body X-axis at the bottom.
(E) cardiac catheterization
Cardiac catheterization for the diagnosis of atrial septal defect and effective method. Currently most scholars believe that. Suspicious or serious cases, lower extremity saphenous vein from cardiac catheter insertion, easy to enter the left atrium through the defect, the pass rate up to 85%. But the cases on the cavity type defects should be taken into the upper extremity venous approach, more convenient.
Implementation of catheterization, the need to pay attention to any abnormal cardiac catheterization schedule, such as cardiac catheterization from the right atrium directly into the left atrium, they can confirm the diagnosis; while also measured the pressure in different parts of the site and collect the blood, check their oxygen content to calculate whether segregation exists, the number from left to right shunt, and pulmonary vascular resistance, and to pay attention to the defects of cardiac catheterization in the upper and lower range, to estimate the size of the defect. The only way to make a correct diagnosis.
In general, patients suffering from atrial septal defect, right atrial blood oxygen content in the superior vena cava often higher than 2 volume%.
As noted above, there are normal people with the hole is not closed dill are generally accounted for 20% to 25%. In this case, cardiac catheter into the left atrium, but no abnormal shunt, right atrial pressure and no change in blood oxygen content, so the difference with atrial septal defect. and surgery in early cases, did not notice this because, there was one case of errors made by surgery. Similarly, if only the oxygen content increased attention to the right atrium, while ignoring the adoption of cardiac catheterization may also cause an error diagnosis. For example, simple right pulmonary venous return, can cause this phenomenon. In short, only cardiac catheter inserted into the left atrium, and right atrial blood oxygen content at the same time more than 2 volume%, superior vena cava, the only sure diagnosis.
If a larger foramen ovale defects. Close to the edge of the right atrial wall, the catheter easily through the defect into the right pulmonary vein and easily misdiagnosed as right pulmonary venous return. However, intubation, such as cardiac catheterization have been estimated through the defect, as it curved toward the tip and can not turn left into the right side, so you can avoid this error. Beware of the right lung venous catheter is inserted, then the time of extubation, cardiac catheterization should be noted that the transfer of cutting-edge direction, can help the differential diagnosis. Venous reflux in the right lung, heart catheterization back, its tip is always toward the right side; and pulmonary vein in the normal position Dependents' return is at the heart, the mind can have a certain degree of catheter tip turned back or left back.
In patients with atrial septal defect; more use of saphenous vein intubation. And upper limb the way into the comparison, this interpolation method is certainly not easy to Chajin pulmonary artery, pulmonary artery pressure that sometimes can not, but proved, in secondary cases of pulmonary hypertension and right ventricular systolic pressure and pulmonary arterial pressure is almost equal ( However, the average pressure slightly lower than the pulmonary artery.) Therefore, the and under the right ventricular pressure and fractional flow can be divided into three five groups of the disease.
Grade : right ventricular systolic pressure less than 60mmHg or mean pressure less than 25mmHg, of which from left to right shunt is less than 20% of pulmonary blood flow, as Group A; greater than 20% as B.
Grade : right ventricular systolic pressure, or an average of between 60 ~ 90mmHg 25-35mmHg pressure in between those points more traffic.
Grade : right ventricular systolic pressure greater than 90mmHg or a mean pressure greater than 35mmHg, of which sub-flows mainly from left to right, as the Group; to mainly from right to left, as B.
The hemodynamic changes of classification groups and, basically, the clinical symptoms and signs, have a certain relationship between the surgical option can be used as a reference.




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