Transposition of the Great Arteries

Thursday, April 7, 2011

Transposition of the great arteries (TGA) is a congenital heart condition in which the pulmonary artery and the aorta are swapped, arising from the wrong ventricle. It is said that they are transposed (switched), which means that they do not originate from their normal position so that the aorta arises from the right ventricle and the pulmonary artery from the left ventricle. In a normal heart it is the other way around: the aorta comes from the left ventricle and the pulmonary artery from the right ventricle. Thus deoxygenated blood that returns from the body goes through the right atrium of the heart and is pumped out by the right ventricle into the pulmonary artery to the lungs to get oxygen; the blood then comes back from the lungs into the left atrium and is pumped out into the aorta by the left ventricle, flowing throught the body to provide the organ tissues with oxygen.

Transposition of the great arteries is sometimes accompanied by other heart defects, such as atrial septal defect (ASD) including patent foramen ovale (PFO), ventricular septal defect (VSD), and patent ductus arteriosus (PDA). Stenosis, or other defects, of valves and/or vessels may also be present. When no other heart defects are present it is called simple transposition of the great arteries; when other defects are present it is called complex TGA.

Transposition of the great vessels is almost always diagnosed in the first hours or days of life due to cyanosis or low oxygen levels. All babies have a patent ductus arteriosus (PDA) at birth that may allow enough mixing to prevent severe cyanosis initially, but as the ductus arteriousus closes, as it typically will in the first hours or days of life, cyanosis becomes more severe. Rapid breathing in response to the low oxygen levels is seen, but the infants are typically described as being "comfortably tachypneic," or not working excessively hard to accomplish this rapid breathing. Symptoms are bluish skin, clubbing of fingers, shortness of breath, etc.

Transposition of the Great Arteries (Video)