Transposition of the great arteries

Question 1

What does transposition mean?

Answer 1

In each others place

Question 2

What are the great arteries?

Answer 2

Pulmonary artery

Aorta

Question 3

Which side of the heart does the aorta normally originate?

Answer 3

Left

Question 4

Which side of the heart does the pulmonary artery normally originate?

Answer 4

Right

Question 5

What is the hallmark feature of transposition of the great arteries?

Answer 5

Ventriculoarterial discordance

Aorta arising from the right ventricle and pulmonary artery arising from the left ventricle

Question 6

Describe how transposition of the great arteries can be fatal

Answer 6

Parallel circulation that results in deep hypoxaemia from lack of mixing and as a result a lactic acidosis and demise
Oxygenated blood only circulates in the pulmonary circulation unless mixing facilitated by another abnormality

Question 7

Name the two types of transposition of the great arteries

Answer 7

Dextro-transposition

Levo-transposition

Question 8

Describe dextro-transposition

Answer 8

Aorta is anterior and to the right of the pulmonary artery

Question 9

Describe levo-transposition

Answer 9

Aorta is posterior and to the left of the pulmonary artery

Question 10

Which transposition class is most common?

Answer 10

Dextro-transposition

Question 11

Which other artery is abnormal in a third of those with transposition of the great arteries?

Answer 11

Coronary artery

Question 12

What is transposition of the great arteries the most common cause of in a newborn?

Answer 12

cyanosis

Question 13

What percentage of all congenital heart diseases does transposition of the great arteries account for?

Answer 13

5-7%

Question 14

Which sex has a higher incidence of transposition of the great arteries?

Answer 14

Male

Question 15

List 3 common anatomic sites of mixing of blood in dextro-transposition of the great arteries

Answer 15

Patent foramen ovale
Ventricular septal defect
Patent ductus arteriosus

Question 16

Describe the how levo-transposition of the great arteries may be acyanotic

Answer 16

Ventricles have switched places as opposed to the arteries and thus deoxygenated blood can return from the systemic circulation and enter the pulmonary circulation to be oxygenated before returning to systemic circulation

Question 17

Describe the effect of levo-transposition

Answer 17

The RV and tricuspid valve are not accustomed for the higher pressures and so over time there is hypertrophy which may lead to tricuspid regurgitation and heart failure

Question 18

Describe the two theories which may explain the mechanism behind transposition of the great arteries

Answer 18

Goor and Edwards - aorta does not rotate normally towards the left ventricle embryologically

De la Cruz - no rotation of the aorto-pulmonary septum at the infundibular level, this causes a 4th aortic arch which later becomes the aorta to interact with the anterior conus on the right ventricle

Question 19

List some maternal risk factors of transposition of the great arteries

Answer 19

Age >40 
Alcohol
Diabetes 
Rubella
Poor nutrition

Question 20

List some clinical features of transposition of the great arteries

Answer 20

Cyanosis (may be mild if some mixing) in first 24hrs

Signs of congestive heart failure - tachypnoea, tachycardia, diaphoresis, failure to gain weight

Question 21

List some examination findings of transposition of great arteries

Answer 21

Prominent right ventricular heave
Single second heart sound, loud A2
Systolic murmur if VSD present
No signs of respiratory distress

Question 22

What investigations should be done for transposition of the great arteries?

Answer 22

Pulse oximetry
Capillary blood gas
Echo
CXR

Question 23

What sign may be seen on CXR in TGA?

Answer 23

Ball on string

Question 24

Describe the management of TGA

Answer 24

Immediate

• Prostaglandin E1 infusion to keep ductus arteriosus open as a temp solution to allow mixing of blood
• correct metabolic acidosis
• emergency balloon septostomy to allow mixing

Long term

• Definitive surgical correction before age 4 weeks - arterial switch operation (ASO)
• Long term follow up and counselling for female patients wishing to get pregnant

Question 25

List some complications of TGA

Answer 25

Neopulmonary stenosis
Neoaortic regurgitation
Neoaortic root dilation
Coronary artery disease
Balloon angioplasty, transcatheter stenting or surgical patch
Sudden cardiac death - primary arrhythmia
Neurodevelopmental abnormalities

Question 26

List some poor prognostic factors

Answer 26

Low gestational age

High pre-operative lactate