Transposition of the great vessels

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Associate Editors-In-Chief: Keri Shafer, M.D. [2]; Atif Mohammad, M.D., Priyamvada Singh, MBBS

Causes

Transposition of the great arteries

• Dextro-transposition of the great arteries/complete transposition of the great arteries
• L-transposition of the great arteries or congenitally corrected transposition of the great arteries

L-TGA or Congenitally Corrected Transposition of the Great Arteries (CCTGA)

Levo-Transposition of the great arteries
ICD-10	Q20.5
ICD-9	745.12
DiseasesDB	13259

Overview

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; and 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 disorders 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.

The letter L in the terms l-TGA or L-TGA refers to the a leftward or Levo aorta, versus the normal dextro or rightward aorta.

Subclassification of TGA

Simple and complex l-TGA

l-TGA is often accompanied by other heart defects, the most common type being intracardiac shunts such as atrial septal defect (ASD) including patent foramen ovale (PFO), ventricular septal defect (VSD), and patent ductus arteriosus (PDA). Stenosis of valves such as pulmonary stenosis or atresia may also be present. Tricuspid regurgitation may be present as well.

When no other heart defects are present it is called 'simple' l-TGA; when other defects are present it is called 'complex' l-TGA.

Pathophysiology

Levo-transposition of the great arteries is a defect in which atrial and ventricular morphologies are discordant, and also the morphology of each ventricle is discordant with the great artery that comes from it. In other words this anomaly is a "double discordance" with both atrioventricular and ventriculoarterial discordance, which essentially "corrects" the physiologic abnormality. The atria are in normal position and received appropriate venous return, but the atria are connected to the opposite ventricle (RA to the LV and LA to the RV). In addition the ventricles are inversely connected to the wrong great artery.

In a normal heart, oxygen-depleted ("blue") blood is pumped from the right atrium into the right ventricle, then through the pulmonary artery to the lungs 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 ejected into the aorta.

History

Congenitally corrected transposition of the great arteries (CCTGA), was first described by Von Rokitansky in 1875.

Epidemiology

Among patients with congenital heart disease, CCTGA has an incidence of 0.5%, with a slight male predominance. 95% of CCTGA occurs in "situs solitus".

Genetics

An increased prevalence in families has been reported.

Diagnosis

Simple l-TGA may be "accidentally" diagnosed in adulthood, as an incidental finding as part of the evaluation or treatment of other conditions.

Symptoms

Simple l-TGA may not yield symptoms in infancy. However, since the morphologic right ventricle normally functions in a low pressure system, the right ventricle may eventually hypertrophy due to increased pressure of ejecting into the systemic circulation of the aorta, and produce symptoms such as dyspnea or fatigue may develop.

Complex l-TGA in contrast, may be associated with symptoms earlier in the natural history of the disase depending on the nature, degree and number of accompanying defect(s). If a right-to-left or bidirectional shunt is present, the list of signs and symptoms may include mild cyanosis. Infants and children can present with congestive heart failure CHF, due to a large VSD or severe tricuspid regurgitation.

Physical Examination

Heart

If there is an associated large VSD, or severe tricuspid regurgitation, these may be detected on physical examination.

Laboratory Findings

Chest X ray

Depending upon underlying associated defects such as a VSD, or severe tricuspid regurgitation, the chest x ray may be abnormal and consistent with these associated defects.

Electrocardiogram

Premature development of heart block may be present.

Echocardiography

l-TGA can sometimes be diagnosed in utero with an ultrasound after 18 weeks gestation.

The following links demonstrate the findings on echocardiography in ccTGA:

LA-RV RA-LV connections

RV-aorta LV-PA connections

Prognosis

Simple l-TGA has a very good prognosis. Most patients are asymptomatic and not require surgical correction.

Treatment

In some cases, the technically challenging "double switch operation" has been successfully performed to restore the normal blood flow through the appropriate morphologic ventricles.

Acknowledgements and Initial Contributors to Page

Leida Perez, M.D.

External links

• Diagram at kumc.edu
• Diagram and description at umich.edu
• Overview at pediheart.org
• Royal Children's Hospital, Melbourne
• Mayo Clinic, Arizona - Florida - Minnesota, USA