SM 147a/148a - CHD Pathology, Pathophysiolgy (congenital)

Question 1

What is the equation that allows us to quantify the severity of a cardiac shunt?

Assume O₂ uptaken by the lungs = O₂ delivered to the tissues

Answer 1

If there is no shunt Q_pulmonary/Q_systemic = 1

(Sat refers to O2 saturation)

Question 2

List 3 indications for surgical closure of a cardiac shunt

Answer 2

1. Failure to thrive in the context of increased respiratory rate
2. The pressure drop through a VSD or PDA is low; this implies that RV pressure is as high as LV pressure, which increases the risk of pulmonary HTN. Repair must be completed before PVR rises/Eisnenmenger physiology manifests
3. The flow through a VSD or PDA is high (Q_Pulm/Q_Sys >1.5); in this case, the LV must work to accomodate the extra flow through the pulmonary circuit. This can cause LV dilation, and increase the risk of dysfunction and failure

Question 3

If a patient has a patent ductus arteriosus, which chamber will pump the extra blood?

Answer 3

LV

-> LV dilation due to volume overload

Risk of long-term failure

Question 4

What size ventricular septal defects will close spontaneously in the first few years of life?

This increases the risk of which cardiac pathology?

Answer 4

Small to moderate VSDs (< 5mm) will close spontaneously

Valve closure increases risk of infective endocarditis

Question 5

In a patent ductus arteriousus, which direction would you expect blood to flow?

What are the effects?

Answer 5

Left (Aorta) -> Right (Pulmonary Artery)

• This will cause volume hypertrophy of the LA and LV
  
  • Increased flow through the pulmonary circulation
  • Increased return to the LA -> LV

Question 6

End-stage pulmonary hypertension due to a L->R shunt is characterized by __________ physiology.

Answer 6

End-stage pulmonary hypertension due to a L->R shunt is characterized by Eisenmenger physiology

Question 7

Increased pressure causes thickening of the _________ of heart valves,

while increased flow causes thickening of the __________ of heart valves.

Answer 7

Increased pressure causes thickening of the edges and line of closure of a heart valve,

while increased flow causes thickening of the entirity of a heart valve.

Question 8

If a patient has an aortopulmonary window, which chamber will pump the extra blood?

Answer 8

LV

-> LV dilation due to volume overload

Risk of long-term failure

(An aortopulmonary window has the same physiology as a patent ductus arteriosus with a larger communication)

Question 9

What is the equation to calculate systemic flow using oxygen saturation?

Answer 9

Question 10

How can a Tet spell be treated rapidly in a person with unrepaired Tetralogy of Fallot?

Answer 10

Squat

This increases systemic vascular resistance to counteract pulmonary resistance

• Decreases R->L shunting
• Increases flow through the pulmonary circuit
• Increases O2 saturation of systemic outflow

Question 11

Describe the differences in cyanotic an acyanotic Tetralogy of Fallot

Answer 11

Tetralogy of Fallot

• Cyanotic
  
  • When pulmonary stenosis causes increased pressure in the right heart, such that the VSD is R->L
• Acyanotic
  
  • Less pulmonary obstruction
  • VSD is L-> R
  • Systemic outflow is more oxygenated

Question 12

What are the 4 types of aortic steosis that can be caused by congenital defects?

Answer 12

1. Valvular level
2. Supravalvular
3. Subarotic stenosis
4. Muscular
   
   1. Asymmetrical septal hypertrophy of the IV septum due to hypertrophic cardiomyopathy

Question 13

Coarctation of the Aorta causes __________ hypertrophy of the ___________, and sometimes the ____________.

Answer 13

Coarctation of the Aorta causes pressure** hypertrophy of the **left ventricle** , and sometimes the **left atrium.

Question 14

What causes ostium primum type atrial shunts?

Which structures are abnormal?

Answer 14

Endocardial Cushion Defect

• Tricuspid and mitral valves may be abnormal
  
  • The shunt is confluent with the atrioventricular valves
  • Regurgitation is possible
  • -> Volume enlargement of the LV

Question 15

Describe the abnormality in blood flow in a PAPVR (Partial Anomalous Pulmonary Venous Return)

Answer 15

Pulmonary veins partially drain into the RA, SVC, or IVC.

This causes the RV to work harder -> RV dilation

Question 16

How can we estimate the pressure drop across a VSD?

Why would we want to do this?

Answer 16

Use ultrasound with doppler to measure the velocity across the VSD; use this to estimate pressure change

We want to do this to assess the need for surgical repair

• If the pressure drop is high, the VSD is restrictive; high LV pressure is not communicated to the right side. This is good!
  
  • However, if flow is high, there is a risk of LV dilation due to increased pulmonary return; surgery is indicated
  • If flow is low, surgery is not indicated
• If the pressure drop is low, the VSD is communicating the high LV pressures to the RV. This increases the risk of pulmonary HTN. Surgery is indicated to close the shunt before Eisenmenger physiology develops

Question 17

Is pulmonary hypertension associated with all shunts?

Why or why not?

Answer 17

Not always!

• All L-> R shunts increase pulmonary flow
• However, the pulmonary vascular tree can usually dilate to accomodate these increases
• Pulmonary hypertension arises due to…
  
  • Large VSD (usually)
  • Patent ductus arteriosus
  • ASD (least commonly)

Question 18

What is the difference between enlargement and dilation of a heart chamber?

Answer 18

Enlargement = Increase in volume of the chamber, unrelated to myocardial failure

Dilation = When elargement is attributed to heart failure

Question 19

If the pressure drop across a VSD is high, is surgical reapair indicated? Why or why not?

Answer 19

If the pressure drop is high, the VSD is restrictive; high LV pressure is not communicated to the right side. This is good!

• If flow through the VSD is low due to high resistance, surgery is not necessary
• However, if flow is high due to low resistance, there is a risk of LV dilation, dysfunction, and eventual failure due to increased pulmonary return; surgery is indicated

Question 20

What congenital defect results in RV outflow to the aorta, and LV outflow to the pulmonary artery?

Answer 20

d-Transposition of the Great Arteries

Question 21

What might cause increased flow to the pulmonary vessels?

How do they react?

Answer 21

Any L->R shunt (ASD, VSD, PDA, PAPVR) will cause flow through the pulmonary vessels to increase.

• Pulmonary vascular resistance (PVR) will increase
• This may prevent the PVR from falling after birth
• If the PVR > SVR, shunting will be reversed, leading to Eisenmenger syndrome/physiology/complex
  
  • End-stage pulmonary hypertension
  • Leads to cyanosis, because blood skips the pulmonary circuit entirely

Pressurized shunts (VSD, PDA) are more likely to cause vascular disease; they increased PVR early in life

Question 22

List the 4 types of atrial shunts

Answer 22

1. Fossa ovalus or secundum (common)
2. Ostium primum
3. Sinus venosus, aka proximal
4. Coronary sinus (rare)

Question 23

What are the 3 basic mechanisms of cyanosis?

Answer 23

1. Arterial connections are reversed (Ex: D-Transposition of the Great Arteries)
2. Atresia or severe hypolasia that blocks flow through the right or left heart
3. Shunt between L & R heart + something that elevates pressure or resistance in the right heart above left sided pressure

Question 24

In a child born with Tetralogy of Fallot, what causes a “Tet spell”?

Answer 24

Anything that causes more vigorous contraction (ex crying)

This causes the RV outflow tract to get even smaller

• Increases R->L shunting
• Decreases oxygenation (due to decreased flow through the pulmonary circuit)
• Further agitation
• Loss of consciousness

Question 25

Which cyanotic lesion may require emergent neonatal intervention for survival?

Answer 25

d-Transposition of the Great Arteries

(Pretty sure about this but not 100%, suggest an edit if you have a better answer!)

Question 26

What is coarctation of the Aorta?

Answer 26

Narrowing of the transverse arch near the isthmus

_{<em>(https://www.drmani.com/coarctation-of-aorta-coa/)</em>}

(between the left subclavian and ductus arteriosus/ligamentum arteriosum)

Question 27

What is tricuspid atresia?

Describe the resulting blood flow

Answer 27

Tricuspid atresia is when the tricuspid valve never develops; there is no path for the blood to flow from the RA to the RV

Tricuspid atresia is usually accompanied by an ASD and a VSD

Blood flow:

• RA -> Through ASD -> LA -> LV ->
  
  • -> Through aorta (normal)
  • -> Through VSD -> RV -> Pulmonary circulation -> LA

_{<em>(https://www.cdc.gov/ncbddd/heartdefects/tricuspid-atresia.html)</em>}

Question 28

Pulmonary capillary wedge pressure is equal to/a proxy for…

Answer 28

• Pulmonary venous pressure
• Left atrial pressure
• Left ventricular filling pressure

Question 29

Describe the pathophysiology of the Eisenmenger Complex

Answer 29

End-stage pulmonary hypertension due to a L->R shunt is characterized by Eisenmenger physiology

• Pulmonary Hypertension leads to…
  
  • Pressure hypertrophy in the RV
  • Decreased volume hypertrophy in the LV
    
    • Can lead to volume atrophy of the LV
• High pressure in the RV + low pressure/atrophy in the LV
  
  • -> Shunt reversal at the ventricular or ductal level
    
    • Less common in ASD
• Blood now bypasses the pulmonary circuit entirely, and the blood pumped out of the heart to the systemic circulation is not oxgenated

Question 30

What is the threshold for Q_pulmonary/Q_systemic above which a shunt is likely to lead to complications?

Answer 30

1.5

Question 31

Which shunts are considered “pressurized shunts?”

Answer 31

VSD

PDA

They are more likely to cause increased PVR earlier in life, increasing the risk of pulmonary vascular disease

Question 32

A patient with a VSD is showing signs of Eisenmenger complex.

Should the VSD be surgically repaired?

Why or why not?

Answer 32

At this point, the VSD should not be surgically repaired.

• Eisenmenger complex = high PVR
• Closing the shunt would force all fo the RV output to go through the high resistance pulmonary circuit
• The RV is not built to pump against high resistance;
  
  • Closing the shunt could cause the patient to fail or decompensate acutely due to very low CO

In general, the patient will do better if the VSD persists. CO will be maintained, even if blood is less than optimally oxygenated. Cyanosis is better tolerated than a crash in CO

Question 33

What is Tetralogy fo Fallot?

Describe the resultant blood flow

Answer 33

Tetralogy of Fallot

All of the following are present:

• VSD
• Pulmonary Stenosis (infundibular)
• Overriding Aorta
• RV Hypertrophy
• Cyanotic (more common)
  
  • RA -> RV->
    
    • -> Pulmonary Artery (little) -> LA -> LV -> Aorta
• *(O₂, but less w/ increasing pulm. stenosis)**
  * -> through VSD -> overriding Aorta (No O₂)
• Acyanotic
  
  • Less pulmonary obstruction
  • VSD is L-> R
  • Flow is the same as above, but there is increased flow through the pulmonary artery, resulting in more oxygenated blood getting to the the body

_{<em>https://www.cdc.gov/ncbddd/heartdefects/tetralogyoffallot.html</em>}

Question 34

If a patient has an ASD, which chamber will pump the extra blood?

Answer 34

RV

-> RV dilation due to volume overload

Can lead to long term failure and risk of atrial arrythmia

Question 35

Why is the murmur associated with VSD often missed in the initial newborn physical exam?

Answer 35

After the baby begins breathing at birth, it takes days-weeks for the pulmonary resistance to fall.

While the pulmonary resistance is still high, the right atrial pressure may be roughly equal to the left atrial pressure, so there isn’t enough shunting yet to cause the VSD murmur

It may take some time after the VSD murmur is heard before pulmonary overcurculation occurs

Question 36

What causes constriction of the ductus arteriosus?

Answer 36

Increased arterial O₂ saturation

Question 37

If the pressure drop across a VSD is low, is surgcial reapair indicated? Why or why not?

Answer 37

Surgical repair is indicated

If the pressure drop is low, the VSD is communicating the high LV pressures to the RV. This increases the risk of pulmonary HTN. Surgery is indicated to close the shunt before Eisenmenger physiology develops

Question 38

What congenital defect results in the failure of the formation of an atrioventricular valve?

Answer 38

Atresia

Ex: Tricuspid atresia

Question 39

What are the clinical manifestations of a shunt?

Answer 39

• Retractions
  
  • Due to increased respiratory rate/effort
• Decreased feeding
• Failure to thrive
  
  • Inadequate growth
  • Eating is hard when respiratory effort is high + lots of calories burned in order to breath

Question 40

In a patient with a complete mixing lesion (ex: atresia with VSD), who is more likely to present evidence of repaired perfusion?

A) A patient with O2 saturation of 85%

B) A patient with O2 saturation of 95%

Answer 40

B) A patient with O2 saturation of 95%

This means that the blood is well oxygenated, but because most of it is getting “stuck” in the pulmonary circulation, and not getting to the systemic

Question 41

Pulmonary stenosis causes ___________ hypertrophy of the ___________.

Answer 41

Pulmonary stenosis causes pressure** hypertrophy of the **right ventricle.

Question 42

Which shunts are not considered “pressurized shunts?”

Answer 42

ASD

PAPVR

They are less likely to cause pulmonary vascular disease, because they typically do not cause increased PVR until later in life

Question 43

The pulmonary vasculature can usually accomodate increaed flow. However, pulmonary hypertension may arise due to one or all of the following changes:

1.

2.

3.

Answer 43

1. Flow beyond the distensibility of the lung vasculature
2. Vasoconstriction of the pulmonary vascular bed
3. Secondary pathologic chanes in the intima and media of the muscular arteries and small arterioles of the lungs
   
   • May occlude the arteries/arterioles
   • -> Restrict the pulmonary bed

Question 44

What kind of hypertrophy would you expect to find in patients with Atrial Septal Defects (ASD)?

Where?

Answer 44

Volume hypertrophy in the Right Atrium and Right Ventricle

-> Increased pulmonic flow -> Thickening of tricuspid and pulmonic valves

Question 45

What kind of shunt would cause volume hypertrophy of the RA and RV only?

Answer 45

Atrial Septal Defect

Increased flow throught the pulmonary system gets shunted from LA to RA => no enlargement of the left side

_{<em>(https://dhg.org.uk/information/atrialseptaldefect.aspx)</em>}

Question 46

Aortic stenosis causes __________ hypertrophy of the ______________.

Answer 46

Aortic stenosis causes pressure** hypertrophy of the **left ventricle.

Question 47

What substance is given to babies with congenital heart defects to maintain patency of the ductus arteriosus?

Answer 47

Prostaglandin E

Note: This won’t help if the baby has d-TGA w/intact septum, or obstructed pulmonary venous return

Question 48

In what cases could a VSD cause pressure hypertrophy of the RV?

Answer 48

If it is large

Pressure in the LV will be transmitted to the RV

Question 49

What is the role of Prostaglandin E in the management of congenital heart defects?

Answer 49

Prostaglandin E maintains patency of the ductus arteriosus

This allows for mixing of blood, converting most emergency situations to elective surgery (necessary, but not this instant)

Exceptions: d-TGA with intact septum, obstructed pulmonary venous return

Question 50

What congenital defect results in all of the following?

• VSD
• Pulmonary Stenosis (infundibular)
• Overriding Aorta
• RV Hypertrophy

Answer 50

Tetralogy of Fallot

• Cyanotic (more common)
  
  • When pulmonary stenosis causes increased pressure in the right heart, such that the VSD is R->L
• Acyanotic
  
  • Less pulmonary obstruction
  • VSD is L-> R
  • A larger volume of oxygenated blood gets to the the body

_{<em>https://www.cdc.gov/ncbddd/heartdefects/tetralogyoffallot.html</em>}

Question 51

A patient with a VSD is being evaluated for surgery. How can we determine whether increased pressure in the right heart is due to the VSD itself, or increased PVR?

(If PVR is too high, surgery is not recomended)

Answer 51

Evaluate the PVR (Wood units)

PVR = (PAP - PVP)/Q_Pulm

If PVR <2, surgery is not contraindicated

PVR 5-7, closure of the shunt poses a risk of acute decompensation or failure

Question 52

What is the equation to calculate pulmonary flow using oxygen saturation?

Answer 52

Question 53

What kind of shunt would cause volume hypertrophy of the RV, LA, and LV, but not the RA?

Answer 53

Ventricular Septal Defect

Blood is shunted from LV -> RV

• Increased blood in the RV -> RV volume hypertrophy
• -> Increased pulmonic flow
• -> Increased blood in the LA -> LA volume hypertrophy
• Extra blood in the LV gets shunted to the RV, but the LV has to also pump extra blood to maintain cardiac output -> LV volume hypertrophy

Question 54

Why are ostium primum type atrial shunts difficult to repair?

Answer 54

• They are confluent with the atrioventricular valves
  
  • Valve repari is difficult in children because they are growing
• They may affect the bundle of His
  
  • May require a pacemaker to repair

Question 55

In an atrial septal defect, which direction would you expect blood to flow?

What are the effects?

Answer 55

From LA -> RA

• Pressure_{(Left atrium)} > Pressure_{(Right atrium)}
• This can cause volume hypertrophy of the RA and RV
  
  • Increase pulmonary flow
    
    • Hemodynamic changes in the tricuspid and pulmonic valves

Question 56

What is d-Transposition of the Great Arteries?

Describe the resultant blood flow

Answer 56

The arterial connections are reversed: The RV outflow is to the aorta, and the LV outflow is to the pulmonary artery.

The systemic and pulmonary circuits are in parallel, rather than in series - oxygenated blood never reaches the body.

Usually d-TGA is accompanied by an ASD (pictured); otherwise, an immediate shunt must be created so the baby can survive to surgery!

_{<em>(https://www.cdc.gov/ncbddd/heartdefects/d-tga.html)</em>}

Question 57

If a patient has a VSD, which chamber will pump the extra blood?

Answer 57

LV

-> LV dilation, risk of failure

Question 58

In a ventricular septal defect, which way would you expect blood to flow?

What are the effects?

Answer 58

From the LV -> RV

• Pressure_{(Left ventricle)} > Pressure_{(Right ventricle)}
• This can cause volume hypertrophy of the RV
  
  • Enlargement of the pulmonic orifice
  • Increased pulmonary flow
  • Hemodynamic changes in the tricuspid and pulmonic valves
• This can lead to volume hypertrophy of the LA and LV
  
  • Enlargement of the mitral valve
  • Hemodynamic changes of the mitral and aortic

Question 59

What might prevent the functional closure of the ductus arteriosus?

What is the effect?

Answer 59

If arterial oxygen saturation is low, there may not be constriction of the ductus arteriosus

It will take longer for the pulmonary resistance to drop, because pressure in the aorta will be transmitted to the pulmonary circuit

The pressures in the RV and PA will be elelevated, but will eventually normalize

Question 60

What is the definition of the Eisenmenger Complex?

Answer 60

Cyanosis in a lesion where you would expect pulmonary overcirculation due to L->R shunting

This occurs when pulmonary vascular resistance is so high that the shunt is reversed (ex: end-stage pulmonary HTN). This results in cyanosis instead of increased pulmonary flow.

Question 61

A patient with a VSD is being evaluated for surgery.

A PVR above _____ would contraindicate surgery; if the VSD were closed, the RV would not be able to pump against a PVR of this magnitude.

Answer 61

A patient with a VSD is being evaluated for surgery.

A PVR above 6 (but above 5 also poses a risk) would contraindicate surgery; if the VSD were closed, the RV would not be able to pump against a PVR of this magnitude.