Right ventricular outflow tract

Introduction The tetralogy of Fallot is one of the most common congenital heart malformations. 3.6 infants with this disease are found in 10,000 births, 12% to 14% in congenital diseases, and the first in cyanotic heart malformations. Bit, accounting for 50% to 90%. In 1988, Fallot made a comprehensive exposition of the four pathological and clinical features of this disease, so later known as the tetralogy of Fallot. In 1944, Blalock first applied shunt surgery to the anastomosis of the subclavian artery to relieve cyanosis. In 1954, Lillehei was the first to succeed in the heart of the controlled crossover cycle and direct vision of Fallot tetralogy. The two major anatomic abnormalities of the quadruple syndrome, right ventricular outflow tract stenosis and ventricular septal defect are quite variable. Right ventricular outflow tract: The right ventricular outflow tract stenosis can be located in the funnel, pulmonary valve, pulmonary valve annulus, pulmonary artery trunk or pulmonary artery branch, and in some cases there may be stenosis in two places.

Cause

The cause of the right ventricular outflow tract:

In 1970, VanPraagh et al considered that the embryonic developmental disorder of tetralogy was due to hypoplasia of the distal segment of the pulmonary artery or the right ventricle. There was no reverse inversion, so the aortic valve remained in the embryonic position, on the right side of the pulmonary valve. The interval of the wall, that is, the wall bundle should be backward and downward when it is normally developed, while the patient with quadruple disease changes its direction to forward and left to the left and stop at the front wall of the cone, so that when the cone is near Right ventricular outflow tract stenosis occurs after cardiac fusion. At the same time, because the interval of the funnel is forward and upward, the gap between the left front upper branch and the right rear lower branch of the baffle is not occupied above the ventricular septum, so that a huge space is formed at the funnel portion interval, that is, the lower back of the upper chamber. Ventricular septal defect, pulmonary plexus dysplasia caused the aortic opening to move to the right, riding over the ventricular septal defect.

an examination

Related inspection

Electrocardiogram cardiac vascular ultrasound

Diagnosis of the right ventricular outflow tract:

The most common major clinical symptoms of tetralogy are purpura and blood hypoxia. The time and severity of presentation of clinical symptoms depends on the extent of right ventricular outflow obstruction and the amount of pulmonary circulation blood flow. In the short term after birth, because the arterial catheter has not been closed, the pulmonary circulation blood flow can come from the patent ductus arteriosus, so the clinical appearance often does not present purpura. In most cases, purpura begins to appear after several weeks or months of arterial catheter closure, and gradually worsens. However, if the right ventricular outflow tract obstruction is severe, such as pulmonary atresia, diffuse dysplasia of the outflow tract, and severe stenosis of the funnel, pulmonary valve, and pulmonary valve, purpura may appear after birth. The right ventricular outflow tract obstruction is mild, and the right to left blood flow is less. The degree of purpura is light. If the ventricular level is divided from left to right, the purpura may not be present. Eating, crying, astringent aggravation during activities, and breathing difficulties.

Child patients like to take a squat position. can reduce the venous return flow of the lower extremities, increase the circulation resistance, so that the blood flow in the lungs increases, the arterial oxygen saturation increases, purpura and dyspnea are alleviated. When the funnel is stenosis, the stenosis is aggravated, and a sudden decrease in pulmonary blood flow can cause hypoxic episodes, which may cause difficulty in breathing, fainting, and convulsions. In severe cases, death can occur. It is more prone to attack when the climate is hot and the body temperature rises. Jet systolic murmurs often weaken or disappear during seizures. Intramuscular injection of morphine 0.2 mg/kg, or propranolol 2.5 mg/kg daily can alleviate hypoxic episodes. In a small number of cases, due to the large ventricular septal defect, the pulmonary vascular resistance decreases from January to February after birth, and the left-to-right sub-flow increases the pulmonary circulation congestion, which may present symptoms of heart failure clinically. But after 6 months of birth, the purpura gradually increased. In cases where the degree of purpura is heavy and red blood cells are significantly increased, thrombosis may occur in the blood vessels of the brain, causing hemiplegia or brain abscess. Cerebral thrombosis is more likely to occur in the absence of water loss. In severe cases of older purpura, the bronchial artery collateral circulation is abundant, and once rupture can cause a large amount of hemoptysis.

Signs: Physical growth is slower. The face, lips, tongue, and eyelid combined with the membrane are obviously purpura. Children's patients with clubbing (toes) are common. The heart sound zone does not expand, and the left front chest can be raised. The systolic murmur caused by the narrowing of the right ventricular outflow tract can be heard between the 2nd and 3rd ribs of the left sternal border, which may be accompanied by tremor. The degree of stenosis is heavy, the blood flow to the aorta is increased in the right ventricle, and the blood flow in the pulmonary arteries is correspondingly reduced, and the noise is reduced, which is short. The systolic murmur of the pulmonary atresia may disappear and be replaced by a continuous murmur produced by the collateral circulation or patent ductus arteriosus. The second heart sound in the pulmonary valve area is weakened or normal, and sometimes a single loud heart sound from the second heart sound of the aortic valve.

Differential diagnosis

Symptoms of confusing right ventricular outflow tract:

Chest X-ray examination: typical cases of quadruple disease show that the heart does not increase, the lung field is abnormally clear, and the vascular pattern is scarce. If the total pulmonary artery is small, the left edge of the heart is flat or concave. If the third ventricle is larger, the left pulmonary artery segment of the heart protrudes. The apex is tilted up due to right ventricular hypertrophy. On the posterior X-ray photograph, the heart shadow is in the shape of a shoe. About 1/4 of the cases have aortic arch on the right side.

Electrocardiogram examination: showing right ventricular hypertrophy and strain, right axis deviation. The R wave of the lead in the right anterior region was significantly increased, and the T wave was inverted. Some patients with lead I and II showed high-point P waves of right atrial hypertrophy. The left front chest lead does not show Q waves, and the R wave voltage is low.

Right heart catheterization: Right heart catheterization shows an increase in right ventricular pressure that reaches the left ventricular pressure level. Cardiac catheterization from the right ventricle directly into the aorta indicates the presence of a ventricular septal defect and an aortic ride. As the right ventricular outflow tract and/or pulmonary stenosis shows a contraction pressure step between the right ventricle and the pulmonary artery. Analysis of the shape of the pressure curve can identify the location, type, and presence or absence of the third ventricle. Arterial oxygen saturation decreased; generally below 89%, further reduced after exercise.

The indicator was injected into the right ventricle and the pulmonary artery via the right heart catheter. The indicator dilution curve in the peripheral artery showed an early appearance of the indicator injected into the right ventricle, and the curve descending showed a bimodal right-to-left shunt curve. An indicator was injected into the pulmonary artery and a normal curve was recorded.

Echocardiography: Cut-to-face echocardiography is valuable for the diagnosis of tetralogy. Can directly show the right ventricular wall thickening; right ventricular outflow tract shows tubular stenosis or formation of the third ventricle; pulmonary stenosis; pulmonary artery diameter is smaller than the aorta; ventricular septal echo and aortic anterior wall right shift, riding across the ventricle Above the interval.

Selective right ventriculography: Selective right ventricular angiography is required before the treatment of tetralogy of Fallot. Cardiac catheter injection contrast agent was placed in the right ventricular chamber. Continuous X-ray film examination showed simultaneous development of the pulmonary artery and aorta and aortic patency. At the same time, the contrast agent entered the left ventricle from the right ventricle through the ventricular septal defect. The angiographic examination can still show the location and extent of the right ventricular outflow tract and/or pulmonary stenosis, understand the pulmonary artery development and measure the diameter of the pulmonary trunk and ascending aorta, and calculate the ratio between the two.

Retrograde aortic angiography: can show patent ductus arteriosus, bronchial artery collateral circulation development and aortic valve opening and closing function. McGoon measures the diameter of the descending aorta of the left and right pulmonary artery and diaphragm. If the ratio of the diameter of the left and right pulmonary artery to the diameter of the descending aorta is greater than 2.0, the pulmonary blood flow is not obstructed.

Blood tests: red blood cell count, hemoglobin and hematocrit were significantly elevated. In severe cases, the red blood cell count can reach 10 million, hemoglobin is 258%, and hematocrit is generally 50-70%, but can also be as high as 90%.

Many hairy congenital heart diseases need to be differentiated from tetralogy of Fallot.

In the infant period, the cyanotic heart malformation differentiated from the quadruple syndrome is: 1 large artery dislocation, cyanosis occurs after birth, the large vascular pedicle narrows, the heart is larger and the pulmonary blood vessels increase or decrease;

2 tricuspid occlusion, with characteristic electrocardiogram, the motor axis is more than 30 ° left and left ventricular hypertrophy;

3 single ventricle with pulmonary stenosis;

4 permanent arterial trunk with small pulmonary artery or no pulmonary artery;

5 right ventricle double outlet with pulmonary stenosis.

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