Common Mixing

Question 1

How does common mixing occur, and how does it present?

Answer 1

1) Atrioventricular septal defect (complete) - A complete AVSD is a defect in the middle of the heart with a single 5-leaflet common valve between the atria and ventricles which stretches across the entire AV junction and tends to leak.
2) Common mixing - breathless and blue
3) Most commonly seen in Down’s syndrome
4) Cyanosis at birth OR heart failure at 2/3 weeks of life
5) No murmur heard

Question 2

Diagnosis of common mixing?

Answer 2

1) ECHO diagnostic

2) ECG septal defect

Question 3

Treatment of common mixing?

Answer 3

1) Treat heart failure medically (diuretics and ACE-i)

2) Surgical repair at 3-6 months

Question 4

What is tricuspid atresia?

Answer 4

• Falls under the category of a complex congenital heart disease - other examples include mitral atresia, double inlet left ventricle, common arterial trunk (truncus arteriosus). Tricuspid atresia commonest!
• Only left ventricle is effective, with the right being small and non-functional
• Commonest complex congenital heart disease
• Common mixing of systemic and pulmonary venous return in the left atrium.

Question 5

Presentation of tricuspid atresia?

Answer 5

1) Cyanosis in the newborn if duct dependent, or child may be well at birth and become cyanosed and breathless.

Question 6

Diagnosis of tricuspid atresia?

Answer 6

ECHO

Question 7

Treatment of tricuspid atresia?

Answer 7

1) In a severely cyanosed child, a shunt can be inserted between subclavian arteries and pulmonary arteries to ensure mixing of blood - Black-Taussig shunt.
2) Complete corrective surgery is not possible due to the fact there is only 1 functioning ventricle - partial solution to connect SVC to PA at 6 months, and IVC to PA at 3-5 years. LV supplies blood to body and systemic venous pressure to lungs - still not fully functional but reduces long-term volume overload on 1 ventricle.