Congenital Heart Disease

Question 0

What can happen when there’s chronically increased pulmonary flow?

Answer 0

Eisenmenger reaction -> scarring, fibrosis -> increased pulmonary vascular resistance (PVR)
(this can cause a L->R shunt to reverse to a R->L cyanotic shunt… but more on this later)
(Fun fact: “Eisenmenger” = “Iron monger” = iron pulmonary vasculature)

Question 1

How does “exercise intolerance” in an infant manifest?

Answer 1

Difficulty feeding.

Question 2

Can anemia mask cyanosis?

Answer 2

Yes. If a patient is significantly anemic, the saturation must be lower before they appear visible cyanotic.

Question 3

Very important concept: What determines which way blood will flow across a septal defect (either atrial or ventricular)?

Answer 3

The resistance of the chambers downstream of those connected by the defect. (eg. for VSD, PVR vs. SVR)
I.e. it’s NOT pressure, because pressure will quickly equalize.

Question 4

Important concept: Does the pulmonary circulation actively modulate how much flow it gets? Does the systemic circulation?

Answer 4

The systemic circulation always gets what it wants “four drops” - and will modify things (e.g. SVR, CO) such that that happens.
The pulmonary circulation does not modulate how much flow it receives. PVR is not actively regulated.

Question 5

3 examples of ways to get Left to Right shunts?

Answer 5

Ventricular septal defect (VSD).
Atrial septal defect (ASD).
Patent ductus arteriosis (PDA).

Question 6

When in systole do murmurs caused by VSD occur?

Answer 6

The murmur is loudest in early systole.

Question 7

What is pre-natal pulmonary vascular resistance like?

What does this do to the RV?

Answer 7

It’s high. (There’s no point in sending much blood flow to the lungs.)
The RV is relatively hypertrophied and less compliant at birth, because of the forces it had to generate. This diminishes with time.

Question 8

What happens in VSD pre-natally and just after birth? Why?

Answer 8

Because PVR is still high, there isn’t actually much flow across the VSD.

Question 9

How does PVR change after birth?

Is this different when there’s VSD?

Answer 9

PVR increases after birth.

When there’s VSD, the decrease in PVR occurs more gradually.

Question 10

If a VSD doesn’t initially have flow across it, when does it start to become a problem?
What pathological changes in the heart then occur?

Answer 10

When PVR drops, blood will flow from L->R across the VSD. (and a systolic murmur will appear)
This causes pressure overload for the RV and increased pulmonary blood flow (PBF), which will lead to volume overload for the LA and LV.

Question 11

How can the volume overload to the left heart in VSD be detected by auscultation?

Answer 11

Volume overload will produce a mid-diastolic murmur due to “relative mitral stenosis.” (not stenosis per se, but diameter is small relative to what would be needed for optimum flow)

Question 12

How do changes in heart caused by ASD (dilated LA and LV, hypertrophied RV) look on ECG?

Answer 12

Increased voltages.

Question 13

So a VSD early on causes increased pulmonary blood flow (PBF) due to L->R shunting. What does this cause in the lungs?
What happens because of this change?

Answer 13

Eisenmenger reaction -> increased PVR.
Increased PVR will cause the direction of flow across the VSD to change - it becomes R->L flow.
This will cause increased RV hypertrophy, and cyanosis.
(the murmur and symptoms of VSD may actually remit for a time before the R->L flow begins).

Question 14

What does VSD do to S2?

Answer 14

Recall S2 is normally split because the pulmonic valve closes after the aortic valve, esp. with inspiration.
VSD with increased PVR from Eisenmenger reaction cause there to be a single S2.
(I’m not sure if this is due to delayed aortic v. closure, or early pulmonic v. closure.)

Question 15

What determines the direction of flow in atrial septal defect?

Answer 15

The compliance of the ventricles.

Question 16

At birth how does LV and RV compliance compare?

What does this mean for flow across an ASD?

Answer 16

They’re about the same -> no net ASD flow.

Recall that the RV is relatively hypertrophied because of high pre-natal PVR.

Question 17

When do ASDs become (easily) detectable, and why?

Answer 17

ASDs are not easily detectable until several months after birth.
By this point, the RV has been doing less work, and has atrophied a bit -> increased compliance.
Increased RV compliance means there will be L->R flow across the ASD, and a murmur will appear.

Question 18

What changes in pressure and/or volume are caused by L->R blood flow in ASD?

Answer 18

RA gets more volume -> dilation -> increased risk for flutter and A fib later in life.
RV also sees more volume and become dilated -> risk of right sided HF later in life.

Question 19

What causes the murmur(s) in ASD?

Answer 19

Increased flow across the pumonic valve -> systolic murmur.
Relative tricuspid stenosis -> diastolic murmur.
Note that flow across the ASD itself does not cause a murmur - the pressure and velocities are too small.

Question 20

What does a murmur from patent ductus arteriosus (PDA) sound like?

Answer 20

Because the pressure in the aorta is always greater than that of the pulmonary artery, there is constant flow and murmur, but it is strongest during systole.

Question 21

Why is patent ductus arteriosus a problem?

Answer 21

Mainly, too much pulmonary blood flow. With time, Eisenmenger’s may develop -> increased PVR -> switch to R->L flow across the PDA -> cyanosis.
(of course, increased PVR has its own problems and can cause heart failure)

Question 22

5 complications of L->R shunts?

Answer 22

CHF secondary to volume and pressure overloads.
Pulmonary vascular disease (Eisenmenger’s).
Growth failure.
Repeated pneumonias.
Endocarditis (wear and tear on valves? turbulent flow -> fibrin?).

Question 23

3 left heart obstructive lesions?

Answer 23

Aortic stenosis.
Aortic coarctation.
Hypoplastic left heart.

Question 24

Say the isthmus between where the left subclavian a. comes off and the descending aorta is really narrow. Why does this not cause problems for a fetus?

Answer 24

The ductus arteriosus has partially oxygenated blood bypassing this narrowed area, so it’s not a problem.

When the DA closes, though, big problems.

Question 25

Say there’s significant aortic stenosis. How can the fetal heart deal with this?

Answer 25

Blood from the DA can flow retrograde through the ascending aorta to service areas (the brain) that would normally receive blood from the PFO / left heart.
The increased DA seems to induce “coarctation” - a little septum like thing in wall of the aorta opposite the DA pointing towards the DA (I like to think that this helps preserve linear flow better a “T” shaped junction).

Question 26

Why is aortic coarctation a problem after birth?

Answer 26

If the DA closes quickly -> shock, especially to areas supplied by the descending aorta.
If the DA closes slowly, there is more time for collaterals to develop… but it’s still not great.

Question 27

What vessels provide collateral blood supply in compensated aortic coarctation? (How can this be seen radiologically?)

Answer 27

Intercostal arteries can provide collateral blood flow from the subclavian arteries.
(Engorged intercostals cause “notching” of the ribs.”)

Question 28

If an infant is dependent on DA blood flow (say due to a fetal hypoplastic aortic arch), how can it be kept open temporarily as a bridge to surgery?

Answer 28

Prostaglandins can maintain DA patency.

Question 29

3 disease manifestations of left heart outflow obstruction?

Answer 29

Increased LA pressure.
Ventricular hypertrophy.
DA dependence.

Question 30

4 complications of left heart obstructive lesions?

Answer 30

CHF from remodeling.
Acidosis and circulatory collapse (if DA closes to quickly).
Sudden death.
Endocarditis.

Question 31

2 categories of cyanotic heart disease?

Answer 31

Pulmonary Blood Flow (PBF) dependent, i.e. improves with more PBF (e.g. tetrology).
PBF independent.

Question 32

Important concept: If there’s unlimited mixing of oxygenated and deoxygenated blood (e.g. in tetrology of Fallot), how does PBF relate to the degree of cyanosis?

Answer 32

More PBF means less cyanosis.

so if you set up a shunt that creates more PBF, you help things a great deal

Question 33

How does PBF relate to SVR and PVR, assuming an unlimited mixing of oxygenated and deoxygenated blood in the heart?

Answer 33

Higher SVR -> more PBF.
(Warm bath -> more cyanosis. Drawing knees to chest -> less cyanosis.)
Higher PVR -> less PBF.

Question 34

There are 4 things wrong in tetrology of Fallot. But really they come from one defect. What is it?

Answer 34

The conal septum is malformed, and grows more into the RV - making a narrow pulmonary valve, pulling over the aortic valve, and creating a VSD.
The LV hypertrophy is reactive.

Question 35

What are the 4 defects in tetrology of Fallot?

Answer 35

Small pulmonary valve.
VSD.
Overriding aorta.
LV hypertrophy.

Question 36

What causes the RV to hypertrophy in tetrology of Fallot?

Answer 36

The VSD.
(don’t think of it as due to the pulmonary stenosis - patients with varying degrees of pulmonary stenosis have been shown to have equivalent degrees of hypertrophy)

Question 37

How do you alleviated tetrology of Fallot?

Answer 37

With a Blalock-Thomas-Taussig shunt:

A shunt is made from a subclavian artery to the pulmonary arteries.

Question 38

What happens in transposition of the great arteries (TGA)?

Answer 38

The aorta comes off the RV, and PA comes off the LV.
Meaning.. the left heart just circulates oxygenated blood through lungs, and right heart just circulates deoxygenated blood through the rest of the body.

Question 39

Does the degree of PBF determine the amount of cyanosis in TGA?

Answer 39

Nope. There’s plenty of PBF in TGA.

Question 40

What 2 parameters determine the degree of cyanosis in TGA?

Answer 40

Size of the septal defect.

Relative ventricular compliances.

Question 41

What can you do to help a infant with TGA immediately, prior to surgery?

Answer 41

Catheter balloon septostomy - make the PFO bigger.

Question 42

How does blood flow across the PFO in TGA, esp. as PVR increases?

Answer 42

It’s complicated.
As PVR decreases, LA/LV compliance will increase (remember we’re in backwards land) -> flow into LA during diastole.
However, when the mitral valve closes, built up volume will flow back into the RA, allowing some oxygenated blood to get into the systemic circulation.

Question 43

What does the Mustard procedure for TGA do?

What’s the problem with this?

Answer 43

It uses a “baffle” in the atria to direct inflow to the opposite side:
i.e. IVC/SVC -> mitral valve -> LV.

Aside from having a lot of stuff hanging out in the atria, the RV still has to do all of the work of pumping systemic circulation, which it doesn’t like to do.

Question 44

What makes an arterial switch for TGA quite complicated?

Answer 44

Well, lots of stuff, but he emphasized that switching the coronary arteries is important.
(they’re cut out and moved so that they’re stretched as little as possible… but the stretching that does happen still leaves them vulnerable for forming thrombi later in life)

Question 45

5 complications/compensations associated with low BPF cyanotic disorders (eg. tetrology)?

Answer 45

Compensatory polycythemia (and Fe deficiency anemia)
Cerebrovascular accidents
Brain abscesses
Growth failure
Bilirubin gallstones (high RBC turnover)

Question 46

2 additional complications that happen in high PBF cyanotic disorders (e.g. TGA) but not in low PBF disorders?

Answer 46

Heart failure.

Pulmonary vascular disease.

Question 47

How is transposition of the great arteries compatible with life?

Answer 47

Mixing of the 2 separate circulations occurs through the patent foramen ovale.