Tetrada Fallo: symptoms, diagnosis, treatment

Tetralogy of Fallot consists of the following 4 congenital defects: a large ventricular septal defect, obstruction of blood flow at the exit of the right ventricle (pulmonary stenosis), right ventricular hypertrophy, and "superior aorta." Symptoms include cyanosis, dyspnea during feeding, failure to thrive, and hypoxemic attacks (sudden, potentially fatal episodes of severe cyanosis). A coarse systolic murmur along the left sternal border in the 2nd-3rd intercostal space with a single 2nd heart sound is often heard. Diagnosis is based on echocardiography or cardiac catheterization. Radical treatment is surgical correction. Endocarditis prophylaxis is recommended.

Tetralogy of Fallot accounts for 7-10% of congenital heart defects. Other defects besides the 4 mentioned above are often present; these include a right-sided aortic arch (25%), abnormal coronary artery anatomy (5%), stenosis of the pulmonary artery branches, the presence of aortopulmonary collateral vessels, patent ductus arteriosus, complete atrioventricular communication, and aortic valve regurgitation.

What is Tetralogy of Fallot?

Tetralogy of Fallot has four components:

• subaortic (high membranous) defect of the interventricular septum, which creates conditions for equalizing pressure in both ventricles;
• obstruction of the right ventricular outlet (pulmonary artery stenosis);
• hypertrophy of the myocardium of the right ventricle due to obstruction of its outlet;
• dextroposition of the aorta (the aorta is located directly above the ventricular septal defect).

The position of the aorta can vary significantly. The last two components have virtually no effect on the hemodynamics of the defect. Stenosis of the pulmonary artery in tetralogy of Fallot is infundibular (low, high and in the form of diffuse hypoplasia), often combined with valvular due to the bicuspid structure of the valve. In children of the first months of life, aortopulmonary collaterals (including the open arterial duct) often function, and in atresia of the pulmonary artery valves (the so-called extreme form of tetralogy of Fallot) - almost always.

The ventricular septal defect (VSD) is usually large; therefore, the systolic pressure in the right and left ventricles (and in the aorta) is the same. The pathophysiology depends on the degree of pulmonary artery obstruction. With mild obstruction, left-to-right shunting of blood through the VSD may occur; with severe obstruction, right-to-left shunting occurs, leading to decreased systemic arterial saturation (cyanosis) that does not respond to oxygen therapy.

Patients with tetralogy of Fallot may suffer from sudden attacks of generalized cyanosis (hypoxemic attacks), which may be fatal. An attack may be precipitated by any condition that slightly reduces oxygen saturation (eg, screaming, defecating) or suddenly reduces systemic vascular resistance (eg, playing, kicking on awakening), or by a sudden attack of tachycardia and hypovolemia. A vicious circle may develop: first, a decrease in arterial PO2 stimulates the respiratory center and causes hyperpnea. Hyperpnea increases systemic venous return to the right ventricle, making the suction effect of negative pressure in the thoracic cavity more pronounced. In the presence of persistent right ventricular outflow obstruction or decreased systemic vascular resistance, increased venous return to the right ventricle is directed into the aorta, thus decreasing oxygen saturation and perpetuating the vicious circle of a hypoxemic attack.

Symptoms of Tetralogy of Fallot

Neonates with significant right ventricular obstruction (or pulmonary atresia) have marked cyanosis and dyspnea when fed with low weight gain. However, neonates with minimal pulmonary atresia may not have cyanosis at rest .

Hypoxemic spells may be precipitated by physical activity and are characterized by paroxysms of hyperpnea (rapid and deep inspirations), restlessness and prolonged crying, increasing cyanosis, and decreased intensity of the heart murmur. The spells most frequently develop in infants; the peak incidence is between 2 and 4 months of age. Severe spells may result in lethargy, convulsions, and sometimes death. Some children may squat during play; this position reduces systemic venous return, probably increasing systemic vascular resistance and thus increasing arterial oxygen saturation.

The leading symptoms of tetralogy of Fallot are dyspnea-cyanotic attacks up to loss of consciousness, developing as a result of spasm of the already stenotic section of the pulmonary artery. Hemodynamic changes: during systole, blood from both ventricles enters the aorta, in smaller quantities (depending on the degree of stenosis) - into the pulmonary artery. The location of the aorta "on top" of the defect of the interventricular septum leads to unimpeded ejection of blood from the right ventricle into it, therefore right ventricular failure does not develop. The degree of hypoxia and the severity of the patient's condition correlate with the severity of pulmonary artery stenosis.

During physical examination, the cardiac area is visually unchanged, systolic tremor is detected parasternally, the boundaries of relative cardiac dullness are not expanded. Tones are of satisfactory volume, a rough systolic murmur is heard along the left edge of the sternum due to pulmonary artery stenosis and blood flow through the defect. The second tone over the pulmonary artery is weakened. The liver and spleen are not enlarged, there is no edema.

In the clinical picture of tetralogy of Fallot, several stages of relative well-being are distinguished: from birth to 6 months, when the child's motor activity is low, cyanosis is weak or moderate; the stage of blue attacks (6-24 months) is the most severe stage clinically, as it occurs against the background of relative anemia without a high hematocrit level. The attack begins suddenly, the child becomes restless, shortness of breath and cyanosis increase, the intensity of noise decreases, apnea, loss of consciousness (hypoxic coma), convulsions with subsequent hemiparesis are possible. The onset of attacks is associated with a spasm of the outflow tract of the right ventricle, as a result of which all venous blood is discharged into the aorta, increasing hypoxia of the central nervous system. An attack provokes physical or emotional stress. With deterioration in health and an increase in hypoxia, children take a forced squatting position. Subsequently, a transitional stage of the defect develops, when the clinical picture acquires features characteristic of older children. At this time, despite the increase in cyanosis, attacks disappear (or children prevent them by squatting), tachycardia and dyspnea decrease, polycythemia and polyglobulia develop, and collateral circulation is formed in the lungs.

Diagnosis of Tetralogy of Fallot

The diagnosis of tetralogy of Fallot is suggested on the basis of anamnesis and clinical data, taking into account chest X-ray and ECG, the exact diagnosis is established on the basis of two-dimensional echocardiography with color Doppler.

ECG helps to detect deviation of the electrical axis of the heart to the right from +100 to +180°, signs of hypertrophy of the myocardium of the right ventricle. Complete or incomplete block of the right leg of the bundle of His is often detected.

Radiologically, a depletion of the pulmonary pattern is detected. The shape of the heart is usually typical - in the form of a "wooden shoe", due to the rounding and raised above the diaphragm apex and the depression of the pulmonary artery arch. The shadow of the heart is small, an increase can be seen with atresia of the pulmonary artery.

EchoCG allows for a diagnosis in most patients to be made with sufficient completeness to determine the treatment tactics. All characteristic signs of the defect are revealed: pulmonary artery stenosis, a large interventricular septal defect, right ventricular hypertrophy and dextroposition of the aorta. Using color Dopplerography, it is possible to record the typical direction of blood flow from the right ventricle to the aorta. In addition, hypoplasia of the outflow tract of the right ventricle, trunk and branches of the pulmonary artery is revealed.

Cardiac catheterization and angiocardiography are performed in case of unsatisfactory echocardiographic visualization of the structures of the heart and blood vessels or in case of detection of any additional anomalies (pulmonary atresia, suspected peripheral stenosis, etc.).

Differential diagnosis of tetralogy of Fallot is carried out, first of all, with complete transposition of the great vessels.

Differential diagnosis of tetralogy of Fallot and transposition of the great vessels

Clinical signs	Congenital heart defect
	Tetralogy of Fallot	Transposition of the great arteries
Timing of the appearance of diffuse cyanosis	From the end of the first to the beginning of the second half of life, up to two years maximum	From birth
History of congestive pneumonia	No	Frequent
Presence of cardiac hump	No	Eat
Expanding the boundaries of the heart	Not typical	Eat
Sonority of the second tone in the second intercostal space on the left	Weakened	Strengthened
Presence of noise	Systolic murmur along the left sternal border	Corresponds to the location of the accompanying communications
Signs of right ventricular failure	None	Eat

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Treatment of tetralogy of Fallot

In newborns with severe cyanosis due to closure of the arterial duct, infusions of prostaglandin E1 [0.05-0.10 mcg/(kg x min) intravenously] are administered to reopen the arterial duct.

In a hypoxemic attack, the child should be placed in a position with the knees pressed to the chest (older children squat on their own and do not develop an attack) and morphine should be administered at 0.1-0.2 mg/kg intramuscularly. Intravenous fluids are given to increase the circulating blood volume. If these measures do not stop the attack, systemic blood pressure can be increased by administering phenylephrine at 0.02 mg/kg intravenously or ketamine at 0.5-3 mg/kg intravenously or 2-3 mg/kg intramuscularly; ketamine also has a sedative effect. Propranolol at 0.25-1.0 mg/kg orally every 6 hours can prevent relapses. The effect of oxygen therapy is limited.

Tetralogy of Fallot is treated in two directions:

• treatment of a dyspnea-cyanotic attack (urgent therapy);
• surgical treatment.

Depending on the anatomical structure of the defect, surgical treatment can be palliative (imposition of an aortopulmonary anastomosis) or radical (elimination of stenosis and plastic surgery of the interventricular septum).

A dyspnea-cyanotic attack is stopped with oxygen therapy, intramuscular injection of trimeperidine (promedol) and niketamide (cordiamine), correction of acidosis and improvement of the microcirculatory bed by intravenous drip of the corresponding solutions (including a polarizing mixture). It is possible to use sedatives and vasodilators. Specific therapy includes beta-blockers, which are first administered slowly intravenously (0.1 mg/kg), and then used orally at a daily dose of 1 mg/kg. Patients with tetralogy of Fallot should not be prescribed digoxin, since it increases the inotropic function of the myocardium, increasing the likelihood of spasm of the infundibular part of the right ventricle.

Palliative surgery - the imposition of interarterial anastomoses of various types (usually a modified subclavian-pulmonary anastomosis) - is necessary when attacks of dyspnea and cyanosis are not relieved by conservative therapy, as well as in case of poor anatomical variants of the defect (pronounced hypoplasia of the pulmonary branches). Palliative surgical options also include balloon dilation of the stenotic pulmonary artery valve, reconstruction of the outflow tract of the right ventricle without closure of the interventricular septal defect. The purpose of these measures is to reduce arterial hypoxemia and stimulate the growth of the pulmonary arterial tree. With the most frequently used technique, the imposition of the subclavian-pulmonary anastomosis according to Blalock-Taussig, the subclavian artery is connected to the unilateral pulmonary artery using a synthetic implant. It is preferable to immediately perform a radical operation.

Radical surgery is usually performed at the age of 6 months to 3 years. The long-term results of the intervention are worse when it is performed at an older age (especially after 20 years).

Complete correction consists of closing the ventricular septal defect with a patch and widening the right ventricular outlet (the stenotic portion of the pulmonary artery). The operation is usually performed electively in the first year of life, but can be performed at any time after 3-4 months of age if symptoms are present.

All patients, whether or not the defect has been corrected, should receive endocarditis prophylaxis before dental or surgical procedures that may result in bacteremia.

Perioperative mortality is less than 3% for uncomplicated tetralogy of Fallot. If tetralogy of Fallot is not operated on, 55% survive to 5 years and 30% to 10 years.