Pediatric patent ductus arteriosus

Introduction to patent ductus arteriosus in children The patent ductus arteriosus (PDA) is a pathological state in which the arterial catheter is not closed and remains open after birth. The arterial catheter is evolved from the distal end of the sixth pair of bronchial arteries. During fetal circulation, most of the blood flow from the right ventricle into the pulmonary artery is directed to the descending aorta and sent to the placenta for oxygenation. After birth, patent ductus arteriosus can exist as an independent lesion (can exist alone) or in combination with other cardiovascular malformations, such as aortic arch constriction or interruption, severe aortic stenosis, left ventricular dysplasia syndrome, and pulmonary artery Atresia, severe pulmonary stenosis or as part of a vascular ring. basic knowledge The proportion of illness: 0.34% Susceptible people: infants and young children Mode of infection: non-infectious Complications: atrial septal defect pneumonia

Causes of patent ductus arteriosus in children

(1) Causes of the disease

The key period of cardiac embryo development is that in the second to eighth weeks of pregnancy, congenital cardiovascular malformations also occur mainly at this stage. There are many reasons for the occurrence of congenital heart disease, which are roughly divided into internal and external types. Among them, the latter are more common, and the internal factors are mainly related to heredity, especially chromosomal translocations and aberrations, such as 21-trisomy syndrome, 13-trisomy syndrome, 14-trisomy syndrome, 15-trisomy syndrome. And 18-trisomy syndrome, etc., often associated with congenital cardiovascular malformations; in addition, the incidence of cardiovascular malformations in children with congenital heart disease is significantly higher than the expected incidence, the most important external factors are intrauterine infection Especially viral infections such as rubella, mumps, influenza and Coxsackie virus; others such as exposure to large doses of radiation during pregnancy, use of certain drugs, metabolic diseases or chronic diseases, hypoxia, maternal age (close to Menopause), etc., all pose a risk of congenital heart disease.

The arterial catheter is an indispensable part of the fetal circulation. After the baby is born, with the establishment of the first breath, the blood oxygen concentration rises sharply, and the muscle of the arterial wall can be contracted and closed. Generally, the arterial catheter is mostly on the first day after birth. It has been functionally closed, but it can be reopened due to lack of oxygen within 7 to 10 days. Anatomical occlusion often needs to be completed in about 1 year old. The histological changes are blood vessels formed by endothelial cells. The intima pad protrudes into the lumen of the arterial catheter, then the subendocardial hemorrhage and necrosis, connective tissue hyperplasia, scar formation, and eventually lead to permanent occlusion of the arterial lumen, forming a cord-like remnant, if the arterial catheter continues to open, constitute There should be no access between the aorta and the pulmonary artery, known as patent ductus arteriosus (PDA).

(two) pathogenesis

The amount and direction of blood flow through the arterial catheter depends on the diameter of the arterial catheter, the length and the relative resistance of the lung and systemic vascular bed. With delivery, umbilical cord ligation, increased systemic vascular resistance, premature infants, due to the number of pulmonary vascular smooth muscle Less, the decline of pulmonary artery resistance is more obvious. When the patent ductus arteriosus is closed, there may be a large left-to-right shunt and left ventricular volume overload, while the premature infants have small myocardial cells, low density, and ventricular muscle water content. More, and the sympathetic nerves in the heart are not fully developed, resulting in a contraction and reserve function of the heart of premature infants. When the ventricular volume is overloaded, the ability to increase the output of the heart beat is often limited, so premature infants especially suffer from In patients with respiratory distress syndrome, congestive heart failure and pulmonary edema often occur due to the opening of the arterial catheter.

When the patent ductus arteriosus is closed, a part of the blood in the aorta is shunted to the pulmonary artery, which causes the peripheral arterial diastolic pressure to decrease and the pulse pressure to widen, and peripheral vascular signs, severe lung disease or persistent pulmonary hypertension, between the main and pulmonary arteries There may be no pressure difference or pulmonary artery pressure exceeding the aortic pressure. At this time, there may be no shunt or right-to-left shunt through the arterial catheter, that is, hypoxic blood in the pulmonary artery flows into the descending aorta to the lower limb, resulting in bruises of the toes, called differential cyanosis. .

Prevention of patent ductus arteriosus in children

The occurrence of congenital heart disease is a comprehensive result of various factors. In order to prevent the occurrence of congenital heart disease, publicity and education of popular science knowledge should be carried out, and key populations should be monitored to give full play to the role of medical staff and pregnant women and their families.

1. Get rid of bad habits, including pregnant women and their spouses, such as smoking, alcohol and so on.

2. Actively treat diseases affecting fetal development before pregnancy, such as diabetes, lupus erythematosus, anemia, etc.

3. Actively do prenatal checkups to prevent colds. Try to avoid using drugs that have been proven to have teratogenic effects and avoid contact with toxic and harmful substances.

4. For older women, there is a family history of congenital heart disease, and one of the couples with serious diseases or defects should be monitored.

Complications of patent ductus arteriosus in children Complications, septal defect, pneumonia

1. Combined with cardiovascular malformation: patent ductus arteriosus can be combined with various cardiovascular malformations, such as atrial septal defect, ventricular septal defect and multiple cardiovascular malformations (pulmonary atresia, aortic arch discontinuity, depending on the arterial catheter supplying pulmonary circulation or systemic blood flow, Complete aortic transposition, etc., most of the aortic arch interrupted combined ductus arteriosus is large, easy to mistaken for the aortic arch, need to pay attention to identification, the aortic arch isthmus is mostly narrow, but no signs of distal expansion can be Differences in aortic coarctation, arterial ductus arteriosus can be combined with aortic coarctation, arterial catheter opening can be at the narrowed distal end, proximal or opposite constriction, aortic pressure changes when the aortic constriction will affect the artery The blood flow velocity of the catheter is not closed.

2. PDA complication of this disease: often complicated by pneumonia, heart failure, bacterial endocarditis and Eisenmenger syndrome.

Symptoms of patent ductus arteriosus in children Common symptoms Cyanosis systolic murmurs three concave signs sacral fingers (toe) water rushing capillary capillaries heart failure systolic tremor breathing shortness diastolic gas-like murmur

Premature infant

Increased blood oxygen partial pressure can make the arterial catheter contract, and prostaglandin E can expand it. The sensitivity of this reaction is related to gestational age. The incidence of patent ductus arteriosus in premature infants is extremely high, and the premature infants below 1750g are about. Half of them have patent ductus arteriosus, and the incidence rate is less than 80% when the weight is less than 1200g. The application of alveolar surfactant improves the symptoms of respiratory distress syndrome, reduces pulmonary vascular resistance, and often causes clinical symptoms. It started to appear about 3 to 4 days later. It can be heard in the second intercostal space on the left side of the sternum. The soft systolic murmur, with the increase of left-to-right shunt, the peripheral pulsation is enhanced, and the anterior region is active. The noise is enhanced and extended to diastole. The typical continuous machine-like murmurs common in older children are rare. The second heart sound in the pulmonary valve area is enhanced. The children without ventilator can show three concave signs and more abdominal examinations. There is a liver enlargement.

2. Baby and older children

(1) Mild: Infants or older children, the smaller patent ductus arteriosus may not cause any symptoms, but the heart murmur is accidentally discovered during routine physical examination, the growth and development are not affected, and the cardiac output is normal or light. Increased degree, no cardiac hypertrophy or abnormal heartbeat, first and second heart sounds are normal, characteristic continuous murmurs can be heard under the left upper edge of the sternum or under the left clavicle. The noise is soft at first, the intensity is gradually increased, and the second heart sound is loudest. , until the diastolic phase is gradually weakened, the small catheter closure of the clinical may only appear as a soft jetting murmur limited to the systolic phase.

(2) medium or large arterial catheter: infants with moderate or large PDA, due to the gradual decrease of pulmonary vascular resistance, increased left-to-right shunt, heart failure symptoms may occur 1 to 2 months after birth, such children are difficult to feed, Excessive sweating, shortness of breath when sucking milk, slower weight gain, lower body length than normal children, respiratory symptoms such as shortness of breath and rib space depression, and a large number of left-to-right shunts can be seen in Harrison ditch, due to increased pulse pressure Infants can show increased peripheral pulsation, while older children show impaired pulsation, increased apical beats in the anterior region, signs of lift-like pulsation and cardiac hypertrophy, and systolic tremor can be reached in the upper left or left clavicle of the sternum. In the presence of pulmonary hypertension, right ventricular hypertrophy, the left sternum can touch the heart beat, auscultation of the second heart sound hyperthyroidism, the first, second heart sounds can be covered by loud arterial catheter murmur, the upper left sternal bone can be heard and multiple The systolic click sound is caused by turbulence caused by the relative blood flow collision between the arterial catheter and the right ventricle. The typical murmur is a continuous rough machine-like murmur, which is the loudest in the late stage of contraction.

(3) Obstructive pulmonary hypertension: a small number of untreated and surviving arterial catheters, due to increased pulmonary vascular resistance, irreversible pulmonary vascular disease will occur, clinical symptoms and signs will change, due to pulmonary vessels As the resistance increases, the left-to-right shunt gradually decreases, and the symptoms of left heart failure are alleviated. Symptom changes often occur 8 to 16 months after birth. The symptoms are weakened, the pulsation of the anterior region is weakened, and the second heart sound is enhanced and single, diastolic. The murmur disappeared, and the phase of the systolic murmur became shorter and gradually disappeared. With the right-to-left shunt, the hairline at the end of the limb appeared obvious, and the sign of the anterior pectoris showed severe pulmonary hypertension. The lungs were 15 to 18 months after birth. Irreversible changes can occur in blood vessels.

Pediatric patent ductus arteriosus examination

Under normal circumstances, routine examination is normal, such as pulmonary infection, endocarditis, bloody infection, increased erythrocyte sedimentation rate, anemia, blood culture positive.

X-ray

The chest tube is normal, the left ventricle is enlarged when there is a large amount of left to right shunt, the left atrium is enlarged obviously, the aorta, pulmonary artery segment is prominent, the peripheral pulmonary vascular shadow is increased, the lung field is congested, and the lung of the premature infant is thickened. Vascular shadow is more difficult to distinguish from pulmonary parenchymal lesions and chronic lung diseases caused by respiratory distress syndrome.

2. ECG

The electrocardiogram of the catheter is completely normal, the diameter of the catheter is larger, the left-to-right shunt is increased, the electrocardiogram shows left ventricular hypertrophy, the R wave of lead II, III, aVF, V5~6 is high, and the left chest lead T wave is inverted; left The enlargement of the room is a broad P wave; if there is pulmonary hypertension, the T wave is high, and the right chest lead R wave is increased. When the premature infant is suffering from lung disease, the right chest lead is dominant.

3. Echocardiography

Two-dimensional ultrasound and Doppler can show the size of the arterial catheter. In the high parasternal section, the probe is placed on the first edge of the sternum, the second intercostal space, and rotated counterclockwise to obtain clear catheter size and shape. Images, other congenital heart diseases, such as pulmonary atresia, transposition of the great arteries and other patent ductus arteriosus can be ideally displayed through the sagittal section of the sternum, left atrium, left ventricular size can reflect left ventricular volume load, M type The ratio of the left atrium to the aortic root diameter of the ultrasound exceeds 1.3, indicating a large left-to-right shunt. Color Doppler can quickly display a small left-to-right shunt, especially for detecting post-operative or transcatheter intervention. Residual shunt, continuous Doppler ultrasound is suitable for estimating the jet velocity through the catheter, and can estimate the pressure difference between the systemic circulation and the pulmonary circulation. This method can be used to estimate the pulmonary artery pressure after the systemic arterial pressure is known.

4. Cardiac catheter

Today's cardiac catheterization is mainly used for patent ductus arteriosus closure rather than for diagnosis. Cardiac catheter detection of elevated pulmonary oxygen saturation indicates that the arterial catheter level is diverted from left to right, but this indicator is not specific. The main pulmonary artery window and the lower ventricle of the double arteries have similar results. The pulmonary artery pressure is increased in the middle to large arterial catheter, and the systolic blood pressure is increased due to the decrease of systemic diastolic blood pressure, resulting in widening of the systemic pulse pressure.

Aortic angiography can show the anatomy of the arterial catheter. Lateral angiography can show the direction and shape of the arterial catheter. The left anterior oblique position can reduce the overlapping of the arterial catheter and the descending aorta. In most cases, the aortic end is wider. The closer the diameter of the pulmonary artery is, the less the tube-like arterial catheter with no segmental stenosis is rare. The catheter can not be passed through the arterial catheter before and during angiography, and the resulting arterial catheter sputum will affect it. The size of the judgment, which affects the choice of the size of the stuffing device.

5.CT and MRI

CT and MRI can better display and diagnose patent ductus arteriosus. MRI examination of patent ductus arteriosus shows a low signal between the upper end of the descending aorta and the beginning of the left pulmonary artery on the T1W image of the transverse spin spin echo. Flowing vascular shadows, abnormal blood flow shadows can be seen here in the gradient echo movie sequence. The contrast-enhanced magnetic resonance angiography sequence is the best for the diagnosis of patent ductus arteriosus. The multi-angle maximum density projection reconstruction can be from the sagittal position. Multiple angles such as left anterior oblique position and transverse position display the direct signs of patent ductus arteriosus, which is helpful for judging the type and size of patent ductus arteriosus. CT diagnosis of patent ductus arteriosus mainly depends on the enhanced scanning transverse position image. To the high-density vascular shadow connected between the upper end of the descending aorta and the beginning of the left pulmonary artery, CT and MRI can not only better display the direct signs of patent ductus arteriosus, but also for other accompanying malformations such as aortic coarctation. Goodly shown or excluded, CT and MRI of patent ductus arteriosus can clearly show left atrial enlargement, left ventricular enlargement, pulmonary artery dilatation, ascending aortic dilation, etc. Ductus help diagnose indirect signs.

6. Cardioangiography

Cardiac angiography of patent ductus arteriosus can be performed by a right heart catheter through the right heart route from the aortic catheter into the descending aorta, and angiography is performed 1.0 to 1.5 cm below the arterial catheter opening. The catheter is selected to be a right heart contrast catheter such as NIH. The contrast agent is 50 mm, 1 to 1.5 ml/kg. By observing the contrast agent to the pulmonary artery, the size and shape of the arterial catheter can be displayed. In addition, the contrast agent can be refluxed to the aortic arch above the arterial catheter opening. The aortic coarctation and aortic arch lesion can be excluded, and the balloon catheter can be inserted from the right heart to the descending aorta. When the angiography is performed, the balloon is firstly blocked to temporarily block the descending aorta blood flow, and the contrast agent can be regulated upward. The transarterial catheter to the pulmonary artery and the ascending aortic arch are especially suitable for neonatal and small infant cases. The right heart catheter can also be used to guide the catheter to the aorta for angiography. This method is complicated.

Cardiac catheter patency can also be performed by left ventricular angiography, through the femoral artery cannula to the left ventricle, ascending aorta, aortic isthmus or proximal arterial catheter opening for angiography, mostly used for patent ductus arteriosus or chamber Septal defect with patent ductus arteriosus, catheter using Pigtail catheter, contrast agent with Omegapak 350, 1 ~ 1.5ml / kg, by observing the contrast agent to the pulmonary artery shunt can show the size and shape of the arterial catheter, and can show or exclude aorta Narrow and aortic arch lesions, if left ventricular angiography can also show or exclude ventricular septal defect.

The position of the patent ductus arteriosus can be used in the left anterior or posterior oblique position. The left anterior or posterior anterior oblique position is the best. The most convenient observation and measurement of the amenorrhea. The shape and size of the catheter, the left side projection is also convenient to measure the angle between the arterial catheter and the descending aorta to determine whether it is a vertical patent ductus arteriosus. For some special patent ductus arteriosus, other projection positions are required. For example, when the right aortic arch is used, the arterial catheter is often connected between the initial part of the left subclavian artery and the beginning of the left pulmonary artery. The orthotopic or aortic elevation of the aorta should be used to show the direct signs of the patent ductus arteriosus. .

Diagnosis and diagnosis of patent ductus arteriosus in children

diagnosis

According to the clinical manifestations, especially the characteristics of the noise, the surrounding capillary signs and the characteristics of X-ray, electrocardiogram and echocardiography, it is not difficult to make a diagnosis for typical cases.

Differential diagnosis

1. Aortic sinus aneurysm rupture: clinical manifestations are easily confused with patent ductus arteriosus. Two-dimensional ultrasound shows sinus wall enlargement at the aortic sinus, rupture at the top, protruding into the right ventricular outflow tract, and abnormal blood flow signals, arteries There was no abnormality in the aortic sinus of the catheter.

2. Aortic-pulmonary septal defect: This disease is rare, which is a septal defect between the congenital aortic root and the pulmonary artery. Two-dimensional ultrasound shows the defect site, size, and ultrasound Doppler abnormality on the short axis of the aortic root. Blood flow originates from the defect and is injected into the main pulmonary artery.

3. Coronary artery-pulmonary artery spasm: abnormal blood flow in the pulmonary artery can be displayed as a fistula, M-shaped color Doppler is a two-stage continuous turbulence, which is different from patent ductus arteriosus, no cerebral pulsation around the child with cyanosis Obviously with continuous murmurs, such as murmurs not in the typical part of the catheter, consider other congenital or acquired heart conditions, such as the main pulmonary artery window, coronary arteriovenous fistula, aortic sinus rupture and room Aortic valve regurgitation of the septal defect.

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