Congenital Heart Defects

Question 1

Why the does the umbilical VEIN that carries O2 blood?

Answer 1

Because in the fetus, the placenta is the organ of respiration. Just like the pulmonary vein taks blood away from the lungs, and umbilical vein takes blood away from the placenta and to the fetus

Question 2

Where does the umbilical vein empty into?

Answer 2

The IVC below the liver

Question 3

What does the ductus venosus do?

Answer 3

Umbilical vein dumps O2 blood into the IVC below the liver.
The ductus venosus then shunts the oxygenated blood past the liver. This saves O2 that is needed to perfuse the heart and brain.

Question 4

Purpose of foramen ovale.

Answer 4

O2 blood that was shunted past the liver via the ductus venosus is traveling at a higher velocity than de-ox blood. This higher velocity blood flows along the eustachian valve and is directed across the foramen oval into the LA.

De-ox blood travels more slowly and goes into the RV, PA, and then through the ductus arteriosus. This way, blood with highest O2 content goes to heart and brain, and lower O2 blood goes elsewhere in the body.

Question 5

Reversal of L vs. R pressure gradients occurs via these mechanisms

Answer 5

1) PVR decreases from first breath d/t lung expansion, increased PaO2 and decreased PaCO2
2) SVR increases from cord clamping (removed placenta from circulation, which was very low resistance)

Question 6

Closure of DA occurs in response to

Answer 6

1) As L and R pressures reverse, so does flow through DA. Exposure to increased PaO2 causes closure
2) The placenta was keeping DA open with circulating PGE1. This is now removed, so DA closes.

Question 7

Closure timing of FO

Answer 7

Functional closure is immediately after cord clamping (reversal of pressure gradients)

Anatomic closure at 3 days

However, it never really closes in about 30% of population. Puts patient at risk for paradoxical embolism.

Question 8

Timing of DA closure

Answer 8

Functional closure = pretty immediate d/t exposure to higher PaO2 and loss of PGE1 release from placenta

Anatomic closure after several weeks

Question 9

These can be used to keep the PDA open or keep the PDA closed

Answer 9

All about manipulating prostaglandins!

Keep it open with:
- PGE1 (mimics action of placenta)

Close it with:
- Indomethacin (prostaglandin synthase inhibitor)

Question 10

Affect of N2O on PVR

Answer 10

N2O decreases PVR

Question 11

Examples of cyanotic shunts

Answer 11

5 Ts!

1) Tetralogy of Fallot
2) Transposition of the great arteries
3) Ebstain’s anomaly (tricuspid abnormality)
4) Truncus arteriosus
5) Total anomalous pulmonary venous connection

Question 12

Examples of acyanotic shunts

Answer 12

VSD
ASD
PDA
Pulmonary stenosis
Coarctation of the aorta

Question 13

4 characteristics of tetralogy of fallot

Answer 13

VSD
Overriding aorta (over both RV and LV)
Pulmonary stenosis
RV hypertrophy

Question 14

Goals of managing kids with tet of fallot

Answer 14

Key is to keep L pressures high and R pressures low

Increase SVR (phenylephrine)
Decrease PVR (avoid situations that cause HPV & can also give N2O)
Maintain contractility and HR
Increase preload (to maintain contractility) 
FiO2 100%
Reduce SNS response --> worsens RVOT obstruction (deepen anesthetic and BBs)
Avoid high PIPs (will worse R side pressures)
Avoid meds that release histamine (will decrease SVR)

Question 15

What is Epstein’s Anomaly?

Answer 15

Downward displacement of tricuspid valve (tricuspid regurgitation) + an ASD (like PFO)

Question 16

Heart with single R ventricle is called this and single L ventricle is called this

Answer 16

Single R = hypo plastic left heart syndrome

Single L = pulmonary atresia