Transposition of great arteries, or TGA for short, is the most common cyanotic congenital heart defect found in newborns. It is associated with a very serious prognosis. Lack of surgical treatment carries a high risk of mortality in the early stages of life. For this reason, it is so important to detect the defect early and carry out the appropriate correction. How common is great truncation (TGA) translation, and what is it caused by?

The translation of great arterial trunks(TGA) accounts for 5-7% of all congenital heart defects. The average incidence is 20-30 per 100,000 live births. Most often, it is an isolated defect, and its etiology is multifactorial and unknown. It is believed to be more common in newborns of mothers with diabetes. Only in 10% of cases is associated with other defects, including with asplenia (lack of spleen) or visceral inversion. TGA occurs 2-3 times more often in boys than in girls.

What is the translation of great arterial trunks?

The translation of great arterial trunks (large vessels) consists in the departure of the aorta from the right ventricle, and the pulmonary trunk from the left ventricle. The connections between the corresponding atria and ventricles remain consistent.

We can distinguish TGA simple (without concomitant defects) and complex.

As a result of such transposition, we deal with the emergence of two separate circulatory systems. Unoxidized blood in the systemic circulation, i.e. system flows from the right atrium to the right ventricle, and from there to the aorta and peripheral vessels, to return to the right atrium via the venous system. In small circulation, blood flows from the left ventricle to the pulmonary circulation, and then oxygenated blood returns to the left atrium. The condition that allows the survival of a newborn with this defect is the existence of connections that allow oxygenated and non-oxygenated blood to mix. They can be:

  • foramen ovale (FO) or atrial septal defect (ASD),
  • defect in the interventricular septum (VSD),
  • patent ductus arteriosus (PDA).

The degree of oxygenation of the body's tissues and the severity of symptoms depend on the number and efficiency of these connections. Gear ratiolarge dishes can be accompanied by:

  • defect in the interventricular septum (VSD) - occurs in about 50% of TGA cases; the more significant it is, the better the mixing of venous and arterial blood; the defect can be single or multiple;
  • aortic coarctation (CoA) - rarely accompanied by TGA;
  • anomalies of departure and course of coronary arteries - in about 1/3 of cases; the most common variant is the departure of the surrounding artery from the right coronary artery;
  • left ventricular outflow tract obstruction - more common in combination with VSD; in simple TGA it is usually functional in nature and results from the displacement of the interventricular septum caused by the higher blood pressure in the right ventricle.

How does TGA manifest?

Babies with big stem transplantation are usually born on time with a normal weight. The main symptom of a newborn baby is central cyanosis - a bluish discoloration of the skin and mucous membranes (mainly the lips, tongue, mouth). It is the result of an increase in the percentage of non-oxygenated hemoglobin in arterial blood (>5g / dl). Cyanosis does not disappear with 100% oxygen. The mileage strongly correlates with the degree of blood mixing. When the only communication between the large and small circulation is the foramen ovale, and the arterial duct is closed in 1-2. One day of life, cyanosis increases rapidly and the clinical condition of the newborn is dramatically deteriorating. However, if the translation is accompanied by a significant loss of the interventricular septum, cyanosis may be slight, and the symptoms of heart failure in the newborn, such as:

  • rapid breathing,
  • tachycardia,
  • sweating,
  • impaired weight gain

can take several weeks to develop.

Treatment of the translation of great arterial trunks

In case of initial TGA diagnosis, immediate administration of PGE1 prostaglandin is first line treatment. The aim of this procedure is to maintain the patency of the arterial duct. The supply of prostaglandin within the first hours after birth enables transport to the appropriate center in the best possible condition. If the mixing of blood at the level of the ductus arteriosus and the interatrial septum is insufficient and the repair operation cannot be performed immediately, the next step is to perform a balloon atrioseptostomy, i.e.Rashkind's treatment . It consists in widening the foramen ovale or breaking the atrial septum. The goal is to increase blood leakage into the right atrium and thus increase the amount of oxygenated blood in the systemic circulation. A balloon-tipped catheter is insertedmost often through the femoral vein to the right atrium, and then through the foramen oval to the left atrium. There, the balloon is filled with a contrast agent diluted in saline. Pulling it towards the right atrium creates a defect in the atrial septum, which will allow for efficient mixing and improvement of arterial blood saturation. Cardiac surgery correction is essential for survival. The type of surgery depends on the anatomical type of the defect. Currently, in the case of simple TGA or TGA with a slight, isolated VSD, the procedure of choice is anatomical correction of the defect -Jatene's operation(arterial switch operation). In short, it consists in a supra-valvular intersection of the aorta and the pulmonary trunk, and then their displacement and anastomosis with the corresponding chambers. The operation also includes transplantation of the coronary arteries to the initial section of the pulmonary artery, which will be connected to the aorta. The stage preceding the procedure is cutting or ligation of the arterial duct. Jatene's operations should be carried out up to 4 weeks of age.

Before the Jatene method became a widely recognized standard, the first TGA repair operation was the so-called physiological correction first performed by Mustard in 1964. It involves removing the atrial septum and connecting the atria with a "cross" dacron or pericardial patch to divert the flow of oxygenated and non-oxygenated blood to the opposite ventricles. It provided adequate saturation, but did not eliminate the ratio, so the right ventricle still had to pump blood into the systemic circulation. When dealing with TGA with coexisting left ventricular outflow tract obstruction and significant VSD, anatomical correction of the defect is not an option. The solution in this situation is operationby the Rastelli method . The closure of the defect is performed in such a way that the blood from the left ventricle drains to the aortic opening. The right ventricle is connected to the pulmonary trunk using a synthetic prosthesis or a homograft (biological graft).

TGA - prognosis after surgery and its side effects

Patients after surgery are subject to vigilant observation in order to detect and treat possible complications, such as:

  • arrhythmias (including sudden cardiac death due to ventricular fibrillation);
  • heart failure;
  • narrowing of the coronary arteries (myocardial ischemia, infarction);
  • aortic and pulmonary stenosis at the site of surgical anastomoses;
  • aortic bulb dilatation and aortic regurgitation.

Variesthe defect correction technique means that each type of surgery is associated with a slightly different set of typical complications.

Each patient, regardless of the type of treatment chosen, should undergo regular control, which includes: medical examination, chest X-ray, ECG, heart echo, saturation measurement.

The prognosis for transposing large vessels depends on the type of defect and the type of procedure performed. If untreated, the defect is associated with a very high mortality. 30% of newborns die within 1 week of life, 50% in the first month of life, and 90% of newborns with TGA die before they reach 1 year of age. Currently, thanks to the better developed neonatal care and pediatric cardiac surgery, the detection and treatment of the translation of great arterial trunks are at a high level, which significantly increases the chances of survival for the youngest patients. For example, long-term survival rates for arterial switch operations (Jatene's operation), depending on the research carried out, reach over 90%. Perioperative mortality (depending on the type of surgery) ranges from several percent.

Sources:

1. Hoffman M., Rydlewska-Sadowska W., Rużyłło W., Wady heart, Warsaw, Wyd. PZWL, 1980, ISBN 83-200-0295-87 Moll J.J., Kopala M., Moll M., Total translation of large vessels, [in:] "Children's Cardiac Surgery" Scientific Publishing House "Śląsk", Katowice 2003, edited by prof. Janusz H. Skalski and prof. Zbigniew Religa (online)

2. Kawalec W. Turska-Kmieć A., Ziółkowska L., Congenital heart defects, [in:] Kawalec W. (ed.), Ziółowska H. (ed.), Grenda R. (ed.), Pediatria, vol. 1 , Warsaw, PZWL, 2016

Category:

Cardiology