Transposition of the Great Arteries, Dextro-Looped

Alternative Names

  • DTGA
  • D-TGA
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WHO-ICD-10 version:2010

Congenital malformations, deformations and chromosomal abnormalities

Congenital malformations of the circulatory system

OMIM Number

608808

Gene Map Locus

12q24

Description

Transposition of the Great Arteries (TGA), the second most common congenital cardiac defect appearing in early infancy, is caused due to abnormal development of the fetal heart during the first eight weeks of pregnancy. As a result of this abnormal development, the two major arteries, the aorta and pulmonary artery, are malpositioned or reversed. Thus, the aorta receives deoxygenated blood from the right ventricle and carries the same blood back into systemic circulation, without undergoing oxygenation. Similarly, the pulmonary arteries receive pure deoxygenated blood from the left ventricle, and carry it back into the lungs once again. Almost 90% of affected infants become cyanotic in the first day of life itself. Some may even show cyanosis within the first few hours. Cyanosis is more severe if other cardiac defects like patent ductus atreriosus are also present. Apart from cyanosis, other common symptoms of the condition include rapid and labored breathing, a rapid heart rate, lack of appetite, weight loss, and cold and clammy skin. About 5-7% of all congenital heart defects are TGA. Interestingly, the condition affects more boys than girls.

Chest X-rays, electrocardiograms, echocardiograms, and/or cardiac catheterization are used to diagnose this congenital defect in infants. Surgery is a must for effective management of the condition. Since the affected individuals are infants, initially, a temporary procedure connecting the two atria may be performed, in order to delay the actual surgical procedure. Surgery may be one of two kinds. The atrial or venous switch (also known as the Mustard or the Senning procedure), involves creating a tunnel between the atria to redirect the oxygenated blood to the right ventricle and the aorta, and the deoxygenated blood to the left ventricle and the pulmonary artery. The other procedure, known as the arterial switch procedure involves switching the two major arteries back to their correct position, connecting the aorta to the left ventricle, and the pulmonary artery to the right ventricle. Patients, however, need to be followed up their entire life for any complications, including decline in cardiac function, arrythmias, and/or endocarditis. Patients are recommended to be on medications for their entire life, and to limit their physical activity.

Molecular Genetics

Most cases of TGA are sporadic, but there are rare reports of familial cases. Incomplete penetrance of the G174 del1 mutation in CFC1 (Cryptic Protein) gene on chromosome 2, along with a splice site duplication in the same gene, have been observed in patients with TGA. This protein, belonging to the Epidermal Growth Factor family is involved in the correct establishment of the left-right axis, and is also supposed to play a role in mesoderm and/or neural patterning during gastrulation. A few mutations in the THRAP2 (Thyroid Hormone Receptor-Associated Protein 2) gene have also been identified in other patients with this condition.

Epidemiology in the Arab World

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Other Reports

Lebanon

In a study to assess the epidemiology of congenital heart disease (CHD) at the American University of Beirut-Medical Center, Bitar et al. (1999) reviewed the medical records of all cardiac patients seen at the outpatient cardiology clinic (OPD) between 1980 and 1995. The incidence of CHD was 11.5/1,000 live births. A relatively low prevalence of complex lesions (i.e., hypoplastic left heart syndrome, transposition of the great arteries)  was observed.

Oman

Sawardekar (2005) conducted a study to establish the prevalence of major congenital malformations in children born during a 10-year period in Nizwa Hospital. Of the 21,988 total births in the hospital, three children were born with TGA.

 

Saudi Arabia

Alshehri (2005) studied the pattern and classification of all major congenital anomalies in Asir region between the years 1997 and 2002. Of the total of 691 neonates born with anomalies, eight were diagnosed with transposition of great arteries. This constituted 7% of neonates with circulatory system anomalies.

Almawazini and AlGhamdi (2011) screened 2610 children from Albaha region with congenital heart disease (CHD).  Of these, 11 patients (1.9%) were found to have TGA.  

United Arab Emirates

Hosani and Czeizel (2000) evaluated the pilot dataset (March-May, 1998) of the UAE National Congenital Abnormality Registry (NCAR). A total of 4,861 births were recorded in this study period, with a birth prevalence of total congenital anomalies being 30.3 per 1,000 births. Transposition of great vessels was identified in four neonates, resulting in an incidence rate of 0.82 per 1,000 births.

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