Complete transposition of the main arteries: symptoms, diagnosis, treatment

Transposition of the great arteries is the most common congenital heart defect of the blue type in children of the first months of life. It accounts for 12-20% of all congenital cardiac anomalies. In older children, due to high mortality, the frequency of this defect is significantly lower. Transposition of the great arteries is 2-3 times more common in boys.

Transposition of the great vessels occurs when the aorta exits the right ventricle and the pulmonary artery exits the left ventricle, resulting in two independent, parallel circulatory systems - pulmonary and systemic. Symptoms primarily include cyanosis and signs of heart failure. Heart auscultation changes depend on the presence of associated congenital defects. Diagnosis is based on echocardiography or cardiac catheterization. Radical treatment is surgical correction. Endocarditis prophylaxis is recommended.

In transposition of the great arteries, the aorta branches off from the right ventricle, and the pulmonary artery branches off from the left. As a result, venous blood is carried by the aorta through the systemic circulation, and oxygenated arterial blood through the pulmonary circulation. Two separate circulations are formed. If there is a communication between them (a defect in the interventricular or interatrial septum, an open aortic duct, an open oval window), the child is viable. The degree of hypoxemia and the magnitude of the cross-flow depend on the size of the communications. A combination of this defect with pulmonary artery stenosis is possible, in which case there is no hypervolemia of the pulmonary circulation, complaints of dyspnea attacks arise, similar to those in tetralogy of Fallot. Hypervolemia in the pulmonary circulation is characterized by complaints of repeated congestive pneumonia.

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Symptoms of transposition of the great arteries

Marked cyanosis develops within hours of birth and progresses rapidly to metabolic acidosis due to decreased tissue oxygenation. Cyanosis is less severe in patients with a large VSD, patent ductus arteriosus, or both, but signs and symptoms of heart failure may develop during the first 3 to 6 weeks of life (eg, tachypnea, dyspnea, tachycardia, diaphoresis, failure to gain weight). Except for generalized cyanosis, physical examination findings are unremarkable. Heart murmurs may be absent unless associated defects are present. The second heart sound is single and loud.

Diagnosis of transposition of the great arteries

In most cases, the defect is diagnosed at birth by diffuse ("cast iron") cyanosis and the presence of severe dyspnea. Noise does not always appear in the first days. It corresponds to the location of the accompanying communication. Systolic tremor is detected by palpation. Cardiomegaly is manifested by the formation of a "heart hump" almost from the first days of life.

An ECG reveals a rightward deviation of the electrical axis of the heart, signs of right ventricular overload and hypertrophy of its myocardium (positive T wave in the right chest leads). In case of large defects of the interventricular septum, signs of left ventricular overload are revealed.

On the radiograph, the pulmonary pattern may be normal (with small communications), enhanced (with large ones) or depleted (in combination with pulmonary artery stenosis). The shadow of the heart has an ovoid shape ("an egg lying on its side").

Echocardiographic diagnostics is based on the identification of the morphology of the ventricles and the main vessels extending from them. The parallel course of the outflow tracts of the ventricles and both vessels in the projection of the long axis of the left ventricle is characteristic.

Cardiac catheterization and angiocardiography have recently lost their importance; they are used to perform the Rashkind procedure and diagnose complex concomitant heart defects.

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Treatment of complete transposition of the great arteries

In the preoperative period, conservative therapy of heart failure is performed. Infusion of prostaglandins of group E is used to improve the patency of the open arterial duct; for the same purpose, closed balloon atrioseptotomy (Rashkind's procedure) is performed to increase the interatrial communication. The procedure is performed under X-ray control or, in modern conditions, in the intensive care unit under ultrasound control. Performing the procedure without intubation makes it possible to quickly activate patients.

In case of transposition of the great arteries accompanied by severe hypoxemia, surgical correction is indicated. Surgical treatment is usually performed early, in the first month of life. There are two main options for surgical treatment: switching of blood flow at the level of the atria and switching of blood flow at the level of the great arteries. Switching of blood flow at the level of the atria is performed by cutting out a Y-shaped patch from the xenopericardium, one end of which is sutured so that venous blood from the vena cava is directed through the atrioventricular communication into the left ventricle. Through the remaining part of the atrium, arterial blood comes from the pulmonary veins through the tricuspid valve into the right ventricle and into the aorta. In case of atrial switching, the right ventricle remains the systemic ventricle. Since it is phylogenetically not designed to work under high pressure, its pumping function and the function of the tricuspid valve gradually deteriorate, which does not allow us to hope for a long-term good result.

Switching the blood flow at the level of the main arteries is a completely radical operation, since the aorta and pulmonary artery are sutured to the corresponding ventricles (to the left and right, respectively). The complexity of the operation lies in the need for coronary angioplasty. The operation is performed under artificial circulation and deep hypothermia (rectal temperature is reduced to 18 °C).