What happens if the pulmonary veins are obstructed ?
We have noted above that in all patients with TAPVC, the amount of blood going to lungs is usually more than twice normal. This in itself causes some increase in pressure in the lungs from increased flow. In addition if the amount of blood coming out of the lungs is blocked (as in obstructed TAPVD) then, due to back pressure, the lung pressure would increase too much to a point of affecting survival. It results in a double injury to the lungs with very high flow and blockage in addition. This results in a true emergency where correction is required almost immediately.