Disease Overview
TetralogyofFallot, also known as cyanosis tetralogy of Fallot, is a combined congenital cardiovascular malformation that includes ventricular septal defect, pulmonary stenosis, right aortic position (riding over the defective ventricular septum) and right ventricular hypertrophy, of which the first two malformations are the basic lesions. cardiovascular disease. Patients with only ventricular septal defects, pulmonary artery orifice stenosis, and right ventricular hypertrophy without aortic span are referred to as atypical tetralogy of Fallot. The incidence is about 11~13% of precordial diseases, and the proportion of men and women is similar. Jiang Xionggang, Department of Cardiac Surgery, Wuhan Union Medical College Hospital
Pathogenesis
Due to the narrowing of the pulmonary artery, the entry of blood into the pulmonary circulation is obstructed, causing compensatory hypertrophy of the right ventricle and an increase in right ventricular pressure. As the aorta straddles the left and right ventricles, it receives blood from both the left and right ventricles to transport the whole body, resulting in cyanosis. However, in young children, cyanosis may be less pronounced or milder because the arterial duct is not yet closed and the blood flow in the pulmonary circulation is increased. In patients with mild stenosis of the pulmonary artery orifice, there may be bidirectional shunting at the ventricular level. The right ventricular pressure is increased and its systolic pressure is equal to that of the left ventricle and aorta, while the right atrial pressure is also increased and the pulmonary artery pressure is decreased.
Clinical symptoms
Most of the cases appear cyanosis in the first few months after birth, and in severe cases, cyanosis appears immediately after birth, shortness of breath after activity, children often feel weak, poor activity tolerance, and may have hypoxic attacks during strenuous activity, crying or early morning when they first wake up: children have sudden respiratory distress and increased cyanosis, which may lead to convulsions and fainting in severe cases. Squatting can increase the resistance of body circulation, reduce the shunt of right heart blood to aorta, thus increase the blood volume of pulmonary circulation and improve hypoxia; squatting can also reduce the lower body’s return blood volume, reduce the right-to-left shunt at the ventricular level, improve the oxygen content of body circulation and improve cerebral hypoxia, a few cases can have epistaxis, hemoptysis, embolism or brain abscess and other symptoms.
2, physical signs can be seen poorly developed, the anterior part of the chest may be elevated, with cyanosis and pestle-like fingers (toes). There is a systolic blowing wind-like jet murmur between the second and third ribs at the left edge of the sternum, which may be accompanied by tremor. This murmur is due to pulmonary stenosis, and its loudness is inversely proportional to the degree of stenosis, because the more severe the stenosis, the more the blood from the right ventricle enters the riding aorta, and the less it enters the pulmonary artery. The other differences between the murmur and simple pulmonary stenosis include shorter duration, earlier peak, reduction rather than enhancement after inhalation of isoamyl nitrite, and less chance of tremor. In severe pulmonary artery stenosis, the murmur may disappear and a continuous murmur may appear, caused by collateral circulation between the bronchial vessels and pulmonary vessels or by a combined unclosed ductus arteriosus. In atypical tetralogy of Fallot and less severe pulmonary stenosis with a left-to-right shunt at the ventricular level, a systolic murmur caused by a ventricular septal defect may be heard between the third and fourth ribs at the left sternal border. The second heart sound in the pulmonary valve area is diminished and split, but it may also be a single, loud sound (transmitted from the second heart sound in the aortic valve area). Systolic jet sounds can be heard in the aortic valve area and are conducted along the left sternal border toward the apex of the heart. The turbinate may be unenlarged or slightly enlarged. There may be elevated pulsations in the precordial and mid-epicardial regions.
Diagnosis
Based on the history, the child has cyanosis, shortness of breath after activity, dyspnea, increased cyanosis, preference for squatting, growth retardation, pestle-like fingers, grade II-III systolic jet murmur between the second and third ribs at the left sternal border, and is diagnosed by electrocardiogram and X-ray examination of right ventricular hypertrophy, aortic widening, boot-shaped heart, echocardiography, cardiac catheterization, and cardiovascular angiography.
Differentiation
The clinical manifestations of this disease are more characteristic and generally not difficult to diagnose, but it needs to be distinguished from other congenital cardiovascular diseases with cyanosis.
(a) Pulmonary artery stenosis combined with atrial septal defect with right-to-left shunt (Farrer’s triad) The cyanosis appears later in this disease. The systolic murmur at the second intercostal space at the left sternal border is louder and occupies a longer period of time, and the second heart sound in the pulmonary valve area is reduced and split. the enlarged cardiac shadow is seen more significantly on X-ray, and the arc of the common pulmonary artery trunk is significantly protruding. Right ventricular strain was more pronounced in the electrocardiogram. The diagnosis can be established by right heart catheterization, selective indicator dilution curve determination, or selective cardiovascular angiography, which reveals a valvular type of pulmonary artery orifice stenosis with right-to-left shunt level at the atrial site.
(b) Eisenmenger syndrome is formed when severe pulmonary hypertension occurs in patients with ventricular septal defect, atrial septal defect, aorto-pulmonary septal defect, or arteriovenous catheterization, converting the left-to-right shunt to a right-to-left shunt. In this syndrome, cyanosis appears late; there are systolic jet sounds and systolic blowing murmurs in the pulmonary valve area, the second heart sound is hyperactive and may be split, and there may be blowing diastolic murmurs; the general trunk arc of the pulmonary artery is clearly protruding on X-ray, and the hilar vascular shadow is thick while the vascular shadow in the pulmonary field is small; the right heart catheterization reveals significant pulmonary artery hypertension, etc., which can be distinguished.
(c) Ebstein’s malformation and tricuspid atresia In Ebstein’s malformation, the septal and posterior leaflets of the tricuspid valve are shifted down to the ventricle, and the right atrium is enlarged while the right ventricle is relatively small, often accompanied by an atrial septal defect that causes right-to-left shunt. Four heart sounds are often heard in the precordial region; X-rays show an enlarged, often spherical, heart shadow, and the right atrium can be very large; electrocardiograms show right atrial hypertrophy and right bundle branch block; selective right atrial angiography shows an enlarged right atrium and a malformed tricuspid valve, which can establish the diagnosis. In tricuspid atresia, the tricuspid orifice is completely inaccessible, and blood from the right atrium enters the left atrium through the unclosed foramen ovale or atrial septal defect, enters the left ventricle through the mitral valve, and then travels to the pulmonary circulation through the ventricular septal defect or unclosed arterial duct. x-ray examination shows an obscure right ventricular site and a clear pulmonary field. The electrocardiogram shows left ventricular hypertrophy. Selective right atrial angiography can establish the diagnosis.
(D) Complete large vessel misalignment: In complete large vessel misalignment, the pulmonary artery originates from the left ventricle while the aortic origin originates from the right ventricle, often accompanied by atrial or ventricular septal defect or ductus arteriosus. Selective right ventriculography may establish the diagnosis. In patients with incomplete large vessel misalignment, both the aorta and pulmonary artery emanate from the right ventricle, and are often associated with ventricular septal defects. If there is also pulmonary valve stenosis, the differential diagnosis will be very difficult.
(v) The immortalized trunk of the artery has only one set of semilunar valves spanning the two ventricles, from which the pulmonary and cephalobrachial arteries emanate, and is often associated with a ventricular septal defect. In patients with tetralogy of Fallot, if the pulmonary artery orifice is severely diseased and atresia of the pulmonary artery and pulmonary valve develops, the presentation is similar to that of trunk immortality and is called pseudo-arterial trunk immortality. It is important to distinguish between the two. For this, selective right ventriculography is helpful.
Ancillary examinations
(a) The lung field is abnormally clear on x-ray, the arc of the common pulmonary artery trunk is inconspicuous or recessed, the right ventricle is enlarged, the apex of the heart is elevated upward, and the heart is shadowed in the shape of a wooden shoe (with a transverse rectangle) on a posterior anterior view. The right aortic arch is seen in nearly ¼ of patients.
(b) Electrocardiographic examination shows right ventricular hypertrophy and strain, with markedly elevated R waves and inverted T waves in all leads of the right precordial region. In some patients, the P waves in the standard leads and the right precordial leads are high and sharp, indicating right atrial hypertrophy. The electrocardiographic axis is right-skewed.
(iii) Echocardiography shows enlargement of the aortic root, which is anteriorly displaced and rides over the ventricular septum. The continuity between the anterior wall of the aorta and the ventricular septum is interrupted, and the septal echogenicity is lost there, while the posterior wall of the aorta and the mitral valve remain continuous. The right ventricle is hypertrophied, and its outflow tract, pulmonary valve or pulmonary artery inner diameter is narrowed. Ultrasonography may also show a right-to-left shunt from the right ventricle to the aorta.
(d) Magnetic resonance computed tomography shows an enlarged ascending aorta riding over the ventricular septum, which is defective, a small common pulmonary artery trunk, stenosis of the funnel of the right ventricle, and stenosis of the pulmonary valve annulus.
(E) Cardiac catheterization Right heart catheterization may reveal the following findings.
1. The systolic pressure step difference between the right ventricle and the pulmonary artery caused by stenosis of the pulmonary artery orifice, and analysis of the morphology of the pressure curve can help determine the type of stenosis.
2. The cardiac catheter may enter the aorta directly from the right ventricle, thus confirming the presence of a riding aortic and ventricular septal defect.
3, A decrease in arterial oxygen saturation to less than 89% indicates a right-to-left shunt. If there is also a left-to-right shunt through the ventricular septal defect, the oxygen content of the right ventricle is higher than that of the right atrium.
(4) In patients with a large ventricular septal defect and a more pronounced right aortic position, the systolic pressure of the aorta, left ventricle and right ventricle are equal.
(vi) Selective indicator dilution curve measurement was performed by injecting indicator (dye or vitamin C, etc.) into the right atrium, right ventricle and pulmonary artery through the right heart catheter, and recording the indicator dilution curve in the peripheral artery (using an otocardiometer or platinum electrode system, etc.), which showed a short right-to-left shunt curve with a bimodal descending curve when the indicator was injected into the right ventricle and its upstream chambers, while the right-to-left shunt curve was recorded when the indicator was injected into the common pulmonary artery and its downstream chambers. In the right ventricle and its upstream chambers, a short right-to-left shunt curve with a bimodal descending curve was recorded, while in the common pulmonary artery and its downstream chambers, a normal curve was recorded.
(vii) Selective cardiovascular imaging is performed by injecting contrast into the right ventricle through the right heart catheter, which reveals the aorta and pulmonary artery simultaneously, and can reveal whether the pulmonary stenosis is valvular, funnel, or pulmonary artery type.
(viii) Routine blood tests are significantly higher in red blood cell count, hemoglobin content and red blood cell pressure.
Treatment
Surgical treatment of this disease is palliative and corrective.
(i) Shunt surgery causes a shunt between the body and pulmonary circulation to increase blood flow to the pulmonary circulation, allowing for an increase in oxygenated blood. There are methods such as anastomosis of the subclavian artery to the pulmonary artery, anastomosis of the aorta to the pulmonary artery, and anastomosis of the vena cava to the right pulmonary artery. This procedure does not change the deformity of the heart itself and is a palliative procedure, but it can create conditions for future corrective surgery.
(2) Direct vision surgery is performed under extracorporeal circulation to repair the ventricular septal defect, cut open the stenotic pulmonary valve or pulmonary artery, and remove the stenosis of the right ventricular funnel, which is a method to completely correct the malformation.