Cardiac Disorders - Right-to-left shunts

Question 1

Right-to-left shunts

Tetralogy of Fallot

Transposition of great arteries

Answer 1

• Presentation is with cyanosis (blue, oxygen saturations ≤94% or collapsed), usually in the first week of life

Management:

• Stabilise the airway, breathing and circulation (ABC), with artificial ventilation if necessary
• Start prostaglandin infusion (PGE, 5 ng/kg per min).

Question 2

Right-to-left shunts

Tetralogy of Fallot

Answer 2

Clinical features:

• large VSDA
• Overriding of the aorta with respect to the ventricular septum
• Subpulmonary stenosis causing right ventricular outflow tract obstruction
• Right ventricular hypertrophy as a result.

Signs

• Clubbing of the fingers and toes will develop in older children
• A loud harsh ejection systolic murmur at the left sternal edge from day 1 of life With increasing right ventricular outflow tract obstruction, which is predominantly muscular and below the pulmonary valve, the murmur will shorten and cyanosis will increase.

Question 3

Right-to-left shunts

Tetralogy of Fallot

Answer 3

ECG:

Normal at birth. Right ventricular hypertrophy when older.

Management:

• Initial management is medical, with definitive surgery at around 6 months of age. It involves closing the VSD and relieving right ventricular outflow tract obstruction
• Infants who are very cyanosed in the neonatal period require a shunt to increase pulmonary blood flow. This is usually done by surgical placement of an artificial tube between the subclavian artery and the pulmonary artery (a modified Blalock–Taussig shunt), or sometimes by balloon dilatation of the right ventricular outflow tract
• Hypercyanotic spells are usually self-limiting and followed by a period of sleep
• sedation and pain relief (morphine is excellent)

Question 4

Right-to-left shunts

Transposition of the great arteries

Answer 4

Clinical features:

• Cyanosis is the predominant symptom
• Presentation is usually on day 2 of life when ductal closure leads to a marked reduction in mixing of the desaturated and saturated blood
• Cyanosis will be less severe and presentation delayed if there is more mixing of blood from associated anomalies, e.g. an ASD
• The second heart sound is often loud and single
• Usually no murmur, but may be a systolic murmur from increased flow or stenosis within the left ventricular (pulmonary) outflow tract

Question 5

Right-to-left shunts

Transposition of the great arteries

Management

Answer 5

• Stabilise the airway, breathing and circulation (ABC), with artificial ventilation if necessary
• Start prostaglandin infusion (PGE, 5 ng/kg per min).
• infants with cyanotic heart disease presenting in the first few days of life are duct dependent; i.e. there is reduced mixing between the pink oxygenated blood returning from the lungs and the blue deoxygenated blood from the body
• Maintenance of ductal patency is the key to early survival of these children
• Observe for potential side-effects – apnoea, jitteriness and seizures, flushing, vasodilatation and hypotension.

Question 6

Right-to-left shunts

Transposition of the great arteries

Answer 6

• The aorta is connected to the right ventricle, and the pulmonary artery is connected to the left ventricle (discordant ventriculo–arterial connection).
• The blue blood is therefore returned to the body and the pink blood is returned to the lungs
• There are two parallel circulations – unless there is mixing of blood between them this condition is incompatible with life
• Fortunately, there are a number of naturally occurring associated anomalies, e.g. VSD, ASD and PDA, as well as therapeutic interventions which can achieve this mixing in the short term

Question 7

Right-to-left shunts

Transposition of the great arteries

Clinical features

Answer 7

• Cyanosis is always present
• The second heart sound is often loud and single
• Usually no murmur, but may be a systolic murmur from increased flow or stenosis within the left ventricular (pulmonary) outflow tract

Question 8

Right-to-left shunts

Transposition of the great arteries

Management

Answer 8

• In the sick cyanosed neonate, the key is to improve mixing.
• Maintaining the patency of the ductus arteriosus with a prostaglandin infusion is mandatory.
• A balloon atrial septostomy may be a life-saving procedure which may need to be performed in 20% of those with transposition of the great arteries
• All patients with transposition of the great arteries will require surgery, which is usually the arterial switch procedure in the neonatal period

Question 9

Right-to-left shunts

Common mixing (blue and breathless)

Atrioventricular septal defect (complete)

Answer 9

This occurs in:

• Atrioventricular septal defect (complete)
• Complex congenital heart disease
• commonly seen in children with Down syndrome
• A complete atrioventricular septal defect (cAVSD) is a defect in the middle of the heart with a single five-leaflet (common) valve between the atria and ventricles which stretches across the entire atrioventricular junction and tends to leak
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Question 10

Right-to-left shunts

Common mixing (blue and breathless)

Atrioventricular septal defect (complete)

Features

Answer 10

Features of a complete atrioventricular septal defect are:

• Presentation on antenatal ultrasound screening
• Cyanosis at birth or heart failure at 2–3 weeks of life
• No murmur heard, the lesion being detected on routine echocardiography screening in a newborn baby with Down syndrome
• There is always a superior axis on the ECG
• Management is to treat heart failure medically (as for large VSD) and surgical repair at 3–6 months of age.