Q 24 Contraindication of Fontan procedure?
a) 20 year old male
b) Severe MR
c) Right pulmonary artery stenosis
d) Left ventricular end diastolic pressure of 20 mm Hg
Fontan procedure is for tricuspid atresia and is done when there is low pulmonary vascular resistance. For the same reason it is not done in neonates.
In Tricuspid atresia, venous blood does not go to right ventricle and there is mixing of venous and arterial blood in aorta which leads to decreased oxygenation.
Most infants with tricuspid atresia have restrictive pulmonary blood flow. To improve systemic oxygentaion they undergo modified Blalock-Taussig shunt, which is a small polytetrafluoroethylene (PTFE) graft to connect the subclavian artery and a pulmonary artery.
Criteria for Fontan procedure are
- Age older than 4 years
- Sinus rhythm
- Normal systemic venous return
- Normal right atrial volume
- Mean pulmonary artery pressure less than 15 mm
- Pulmonary arteriolar resistance less than 4 Wood units/m 2
- Pulmonary artery–aorta ratio more than 0.75
- Left ventricular ejection fraction more than 0.60
Current absolute contraindications are a pulmonary vascular resistance above 4 Wood units/m2, severe hypoplasia of the pulmonary arteries, and severe diastolic dysfunction of the left ventricle.