True about co-arctation of aoa -

Ans. is 'a' i.e., Most common site is distal to the origin of left subclan aery Most common site of COA is distal to the origin of left subclan aery. Hemodynamics of COA during fetal life o In fetal life, blood from right ventricle passes to pulmonary aery and then to descending aoa through ductus aeriosus. o Blood from left ventricle passes to Aoa and then to innominate, left carotid and left subclan aery. o If constriction (coarctation) is proximal to ductus aeriosus (preductal or infantile coarctation), there is no obstruction to flow because constriction is not obstructing the flow of upper limb and lower limb ---> Collaterals are not formed. o If the constriction is distal to ductus aeriosus (post ductal or adult type coarctation of aoa), it causes obstruction of flow of desending aoa, and pas of body that are supplied by descending aoa, have impaired circulation -4 This stimulates formation of collaterals in fetal life. Hemodvnamics after bih o After bih, ductus aeriosus closes, so that blood flow to descending aoa from right ventricle does not occur and descending aoa must receive its total supply from left ventricle ascending aoa. o But there is obstruction due to coarctation. o In preductal coarctation, there are no collaterals --> Neonates become symptomatic immediatly --> Hypeension results in CHF. o In postductal coarctation, due to presence of collaterals neonates are spared from developing hypeension & CHF. o Due to obstruction, there is pressure overload to left ventricle Left ventricular hyperophy.