Student questions about congenital heart defects


I received a bunch of great questions from a student in my pathology course, and thought I’d share them with you. I think reading about things in in question/answer format helps the material stick in your head. These particular questions are about congenital heart defects.

Q. Can VSD and PDA also lead to the same pulmonary problems as ASD since they are all left to right shunts?
A. Yes! Any left-to-right shunt, if it is big enough, can eventually put enough pressure on the right side of the circulation that the lungs respond by constricting vessels and laying down fibrotic tissue, leading to pulmonary hypertension. Eventually, if pressures on the right side exceed those on the left, the shunt reverses, becoming a right-to-left shunt.

Q. What is the effect/outcome of the overriding aorta in Tetralogy of Fallot?
A. The main problem in Tetralogy of Fallot is the pulmonary outflow obstruction – that really determines the extent and severity of the clinical picture. The overriding aorta doesn’t contribute much. It does allow unoxygenated blood to flow directly into the aorta, which doesn’t help matters. There already is a ventricular septal defect, which allows mixing of blood, so the overriding aorta would just exacerbate that mixing, making it even easier for blood to bypass the lungs and go straight to the peripheral circulation. Which manifests as cyanosis.

Q. Can you surgically repair transposition of the great arteries?
A. Yes. Patients with TGA usually have some sort of shunt as well (like a VSD) – and depending on the degree of shunting, they may be fairly stable for a little while. However, most of the time, the transposition is repaired surgically within weeks of birth.

Q. Is mitral valve prolapse an insufficiency since it cannot close properly?
A. Yes – that’s exactly right. Insufficiency means the valve can’t close properly; stenosis means it can’t open properly. In mitral valve prolapse, the leaflets are floppy, and they don’t come together like they should, so during diastole, blood regurgitates into the left atrium.