Transposition of the great arteries Flashcards
What does transposition mean?
In each others place
What are the great arteries?
Pulmonary artery
Aorta
Which side of the heart does the aorta normally originate?
Left
Which side of the heart does the pulmonary artery normally originate?
Right
What is the hallmark feature of transposition of the great arteries?
Ventriculoarterial discordance
Aorta arising from the right ventricle and pulmonary artery arising from the left ventricle
Describe how transposition of the great arteries can be fatal
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
Name the two types of transposition of the great arteries
Dextro-transposition
Levo-transposition
Describe dextro-transposition
Aorta is anterior and to the right of the pulmonary artery
Describe levo-transposition
Aorta is posterior and to the left of the pulmonary artery
Which transposition class is most common?
Dextro-transposition
Which other artery is abnormal in a third of those with transposition of the great arteries?
Coronary artery
What is transposition of the great arteries the most common cause of in a newborn?
cyanosis
What percentage of all congenital heart diseases does transposition of the great arteries account for?
5-7%
Which sex has a higher incidence of transposition of the great arteries?
Male
List 3 common anatomic sites of mixing of blood in dextro-transposition of the great arteries
Patent foramen ovale
Ventricular septal defect
Patent ductus arteriosus
Describe the how levo-transposition of the great arteries may be acyanotic
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
Describe the effect of levo-transposition
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
Describe the two theories which may explain the mechanism behind transposition of the great arteries
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
List some maternal risk factors of transposition of the great arteries
Age >40 Alcohol Diabetes Rubella Poor nutrition
List some clinical features of transposition of the great arteries
Cyanosis (may be mild if some mixing) in first 24hrs
Signs of congestive heart failure - tachypnoea, tachycardia, diaphoresis, failure to gain weight
List some examination findings of transposition of great arteries
Prominent right ventricular heave
Single second heart sound, loud A2
Systolic murmur if VSD present
No signs of respiratory distress
What investigations should be done for transposition of the great arteries?
Pulse oximetry
Capillary blood gas
Echo
CXR
What sign may be seen on CXR in TGA?
Ball on string
Describe the management of TGA
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
List some complications of TGA
Neopulmonary stenosis
Neoaortic regurgitation
Neoaortic root dilation
Coronary artery disease
Balloon angioplasty, transcatheter stenting or surgical patch
Sudden cardiac death - primary arrhythmia
Neurodevelopmental abnormalities
List some poor prognostic factors
Low gestational age
High pre-operative lactate
