Surgery with PDA Question

[wanderlustin]

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i'm reading step up 2 medicine and it says that with a PDA, if severe pulm HTN or a right-to-left shunt is present, surgery is contraindicated.

does anyone know why this might be? is it just cause the shunt won't reverse back after surgery?

 

[dienekes88]

Eisenmenger Syndrome.

Think about it this way. The pulmonary circulation is supposed to be low pressure. Given extensive volume overload (Aorta-to-LPA), there will be intimal proliferation and medial hypertrophy with fibrosis. As a result, you get increased pulmonary vascular resistance. If the resistance is so high that you have right-to-left shunting, then that's a heck of a lot of resistance. Acutely loading the right ventricle like that will lead to decompensation and death. I'm not sure if the pulmonary hypertension would be amenable to the typical stuff for pulmonary hypertension: nifedipine, sildenafil, bosentan, IV epoprostenol, etc. I think it might be since congenital heart disease leading to PH is in Group I of the Dana Point update to the Evian Classification of pulmonary hypertension.

 

[OveractiveBrain]

Eisenmenger Syndrome.

Think about it this way. The pulmonary circulation is supposed to be low pressure. Given extensive volume overload (Aorta-to-LPA), there will be intimal proliferation and medial hypertrophy with fibrosis. As a result, you get increased pulmonary vascular resistance. If the resistance is so high that you have right-to-left shunting, then that's a heck of a lot of resistance. Acutely loading the right ventricle like that will lead to decompensation and death. I'm not sure if the pulmonary hypertension would be amenable to the typical stuff for pulmonary hypertension: nifedipine, sildenafil, bosentan, IV epoprostenol, etc. I think it might be since congenital heart disease leading to PH is in Group I of the Dana Point update to the Evian Classification of pulmonary hypertension.

Correct, here it is again in dumb-speak:

Force required to pump blood forward through the lungs is now so great that the right ventricle just cant do it. Closing the hole (so only the right ventricle can work on the lungs) is like having a massive pulmonary embolus. Right heart cant push blood through the lungs, left heart cant get any blood, body cant get any blood, blood pressure down, death.

With the patent PDA, even though the blood the right heart pushes into the left heart is less oxygenated than in a normal person, at least there's some flow right to left.

Also keep in mind, at this stage of disease, the patient isn't doing well, so won't likely benefit very much from the surgery anyway... they've probably got months to live... if that