Absent branch pulmonary artery in Tetralogy of Fallot
Absent branch pulmonary artery occurs in 10% of Tetralogy of Fallot. Absent branch pulmonary artery occurs opposite to the side of aortic arch in Tetralogy of Fallot while it is on the side of the aortic arch in truncus arteriousus.
Side of classic Blalock – Taussig shunt
Classic Blalock – Taussig shunt (BT shunt) is done on the side opposite to that of the aortic arch so that the presence of brachiocephalic trunk prevents kinking of the subclavian artery which is mobilised down to anastamose with the pulmonary artery branch on the same side. In classic BT shunt the subclavian artery is divided proximal to the origin of vertebral artery and there is a chance for subclavian steal syndrome. During arm exercise, reverse flow occurs in the vertebral artery to the exercising limb so that basilar artey flow is reduced and the person may feel giddiness or develop syncope.