Levo-Transposition of the great arteries
Encyclopedia
levo-Transposition of the great arteries (L-Transposition of the great arteries, levo-TGA, or l-TGA), also commonly referred to as congenitally corrected transposition of the great arteries (CC-TGA), is an acyanotic
congenital heart defect
(CHD) in which the primary arteries (the aorta
and the pulmonary artery
) are transposed, with the aorta anterior and to the left of the pulmonary artery; the morphological left and right ventricles
are also transposed.
Use of the term "corrected" has been disputed by many due to the frequent occurrence of other abnormalities and or acquired disorder
s in l-TGA patients.
In segmental analysis
, this condition is described as atrioventricular discordance (ventricular inversion) with ventriculoarterial discordance.
l-TGA is often referred to simply as transposition of the great arteries (TGA); however, TGA is a more general term which may also refer to dextro-transposition of the great arteries
(d-TGA).
Another term commonly used to refer to both l-TGA and d-TGA is transposition of the great vessels
(TGV), although this term can have an even broader meaning than TGA.
, oxygen
-depleted ("blue") blood is pumped from the right atrium into the right ventricle, then through the pulmonary artery to the lung
s where it is oxygenated. The oxygen-rich ("red") blood then returns, via the pulmonary veins, to the left atrium from which it is pumped into the left ventricle, then through the aorta to the rest of the body, including the heart muscle itself.
With l-TGA, blue blood is pumped from the right atrium into the morphological left ventricle (which lies on the right side of the heart), then through the pulmonary artery to the lungs. The red blood then returns, via the pulmonary veins, to the left atrium from which it is pumped into the morphological right ventricle, then through the aorta.
such as atrial septal defect
(ASD) including patent foramen ovale (PFO), ventricular septal defect
(VSD), and patent ductus arteriosus
(PDA). Stenosis
of valve
s or vessels
may also be present.
When no other heart defects are present it is called 'simple' l-TGA; when other defects are present it is called 'complex' l-TGA.
, the right ventricle may eventually hypertrophy due to increased pressure and produce symptoms such as dyspnea
or fatigue
.
Complex l-TGA may produce immediate or more quickly-developed symptoms, depending on the nature, degree and number of accompanying defect(s). If a right-to-left or bidirectional shunt is present, the list of symptoms may include mild cyanosis
.
d in utero with an ultrasound
after 18 weeks gestation
. However, many cases of simple l-TGA are "accidentally" diagnosed in adulthood, during diagnosis or treatment of other conditions.
and not requiring surgical correction.
In a number of cases, the (technically challenging) "double switch operation" has been successfully performed to restore the normal blood flow through the ventricles.
Acyanotic heart defect
----Acyanotic heart defect have normal levels of oxyhemoglobin saturation in systemic circulation. This tends to be left to right side heart shunts, whereas cyanotic heart disease is right to left shunts which lowers oxygen saturation level....
congenital heart defect
Congenital heart defect
A congenital heart defect is a defect in the structure of the heart and great vessels which is present at birth. Many types of heart defects exist, most of which either obstruct blood flow in the heart or vessels near it, or cause blood to flow through the heart in an abnormal pattern. Other...
(CHD) in which the primary arteries (the aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
and the pulmonary artery
Pulmonary artery
The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood....
) are transposed, with the aorta anterior and to the left of the pulmonary artery; the morphological left and right ventricles
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...
are also transposed.
Use of the term "corrected" has been disputed by many due to the frequent occurrence of other abnormalities and or acquired disorder
Acquired disorder
An acquired disorder is a medical condition which develops post-fetally; in contrast with a congenital disorder, which is present at birth. A congenital disorder may be antecedent to an acquired disorder ....
s in l-TGA patients.
In segmental analysis
Segmental analysis (biology)
Segmental analysis is a method of anatomical analysis for describing the connective morphology of the human body. Instead of describing anatomy in terms of spatial relativity, as in the anatomical position method, segmental analysis describes anatomy in terms of which organs, tissues, etc...
, this condition is described as atrioventricular discordance (ventricular inversion) with ventriculoarterial discordance.
l-TGA is often referred to simply as transposition of the great arteries (TGA); however, TGA is a more general term which may also refer to dextro-transposition of the great arteries
Dextro-Transposition of the great arteries
dextro-Transposition of the great arteries , sometimes also referred to as complete transposition of the great arteries, is a birth defect in the large arteries of the heart...
(d-TGA).
Another term commonly used to refer to both l-TGA and d-TGA is transposition of the great vessels
Transposition of the great vessels
Transposition of the great vessels is a group of congenital heart defects involving an abnormal spatial arrangement of any of the primary blood vessels: superior and/or inferior vena cavae , pulmonary artery, pulmonary veins, and aorta...
(TGV), although this term can have an even broader meaning than TGA.
Overview
In a normal heartHeart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
, oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
-depleted ("blue") blood is pumped from the right atrium into the right ventricle, then through the pulmonary artery to the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s where it is oxygenated. The oxygen-rich ("red") blood then returns, via the pulmonary veins, to the left atrium from which it is pumped into the left ventricle, then through the aorta to the rest of the body, including the heart muscle itself.
With l-TGA, blue blood is pumped from the right atrium into the morphological left ventricle (which lies on the right side of the heart), then through the pulmonary artery to the lungs. The red blood then returns, via the pulmonary veins, to the left atrium from which it is pumped into the morphological right ventricle, then through the aorta.
Simple and complex l-TGA
l-TGA is often accompanied by other heart defects, the most common type being intracardiac shuntsShunt (medical)
In medicine, a shunt is a hole or a small passage which moves, or allows movement of fluid from one part of the body to another. The term may describe either congenital or acquired shunts; and acquired shunts may be either biological or mechanical.* Cardiac shunts may be described as...
such as atrial septal defect
Atrial septal defect
Atrial septal defect is a form of congenital heart defect that enables blood flow between the left and right atria via the interatrial septum. The interatrial septum is the tissue that divides the right and left atria...
(ASD) including patent foramen ovale (PFO), ventricular septal defect
Ventricular septal defect
A ventricular septal defect is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart.The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes.The membranous...
(VSD), and patent ductus arteriosus
Patent ductus arteriosus
Patent ductus arteriosus is a congenital disorder in the heart wherein a neonate's ductus arteriosus fails to close after birth. Early symptoms are uncommon, but in the first year of life include increased work of breathing and poor weight gain...
(PDA). Stenosis
Stenosis
A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....
of valve
Valve
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...
s or vessels
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
may also be present.
When no other heart defects are present it is called 'simple' l-TGA; when other defects are present it is called 'complex' l-TGA.
Symptoms
Simple l-TGA does not immediately produce any visually identifiable symptoms, but since each ventricle is intended to handle different blood pressuresBlood Pressures
Blood Pressures is the fourth studio album by indie rock band The Kills. It was released on April 1, 2011 in the Republic of Ireland, Germany, Nordic Countries and Austria, in the UK on April 4, 2011, and in the United States on April 5, 2011....
, the right ventricle may eventually hypertrophy due to increased pressure and produce symptoms such as dyspnea
Dyspnea
Dyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...
or fatigue
Fatigue (physical)
Fatigue is a state of awareness describing a range of afflictions, usually associated with physical and/or mental weakness, though varying from a general state of lethargy to a specific work-induced burning sensation within one's muscles...
.
Complex l-TGA may produce immediate or more quickly-developed symptoms, depending on the nature, degree and number of accompanying defect(s). If a right-to-left or bidirectional shunt is present, the list of symptoms may include mild cyanosis
Cyanosis
Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is...
.
Diagnosis
l-TGA can sometimes be diagnoseMedical diagnosis
Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...
d in utero with an ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
after 18 weeks gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
. However, many cases of simple l-TGA are "accidentally" diagnosed in adulthood, during diagnosis or treatment of other conditions.
Treatment and Prognosis
Simple l-TGA has a very good prognosis, with many individuals being asymptomaticAsymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
and not requiring surgical correction.
In a number of cases, the (technically challenging) "double switch operation" has been successfully performed to restore the normal blood flow through the ventricles.