Congenital Heart Disease

Question 1

When does congenital heart disease usually happen?

Answer 1

• arise during embryogenesis
• usually weeks 3 - 8
• seen in 1% of live births
• most defects are sporadic

Question 2

What is Right to Left shunting also known as?

Answer 2

• cyanotic heart disease
• deoxygenated blood enters in systemic circulation

Question 3

What 5 things cause Right to Left shunts?

Answer 3

1. Tetralogy of Fallot
2. Transposition of great vessels
3. Persistent Truncus Arteriosus
4. Tricuspid Atresia
5. Total anomalous pulmonary venous connection

Question 4

What is characteristic of Left to Right shunting?

Answer 4

• asymptomatic at birth
• shunt can eventually reverse
• called Acyanotic

Symptoms:
- signs of heart failure
- exercise intolerance
- shortness of breath
- poor feeding and failure to thrive in infants

Question 5

What is Reversal of Left to Right shunt?

Answer 5

What is a Left-to-Right Shunt?
* Normally, blood flows from the left side of the heart (high pressure) to the right side (lower pressure) through defects like ASD, VSD, or PDA.
* This causes extra blood flow to the lungs, but oxygenated blood still reaches the body — so no cyanosis yet.

⸻

What Happens Over Time?
1. The lungs get overloaded with extra blood → pulmonary vessels react by thickening and narrowing (pulmonary vascular remodeling)
2. This causes pulmonary hypertension (high pressure in lung arteries)
3. Pulmonary artery pressure rises and may match or exceed systemic pressure

⸻

What is Reversal of the Shunt?
* Once pulmonary pressure ≥ systemic pressure, the pressure difference flips.
* So now, instead of blood flowing left → right, it flows right → left through the defect.
This condition is called Eisenmenger Syndrome.
* The original left-to-right shunt reverses to right-to-left shunt
* Irreversible pulmonary vascular disease sets in
* Cyanosis and complications develop

Question 6

What is Eisenmenger Syndrome?

Answer 6

• increased pulmonary resistance happens due to original right to left shunt, then it causes it to reverse and become a left to right shunt, increasing pulmonary flow and pulmonary resistance (called a reversal of shunt)
• this leads to late cyanosis, right ventricular hypertrophy, polycythemia and clubbing
• there is polycythemia because low hemoglobin levels due to decreased oxygen leads to the production of erythropoietin
• There is clubbing due to the release of local vasodilators in response to chronic hypoxemia

Question 7

What are the causes of Left to Right shunts?

Answer 7

1. ASD
2. VSD
3. PDA

• small defects often asymptomatic
• large defects can lead to Eisenmenger syndrome, this is pulmonary hypertension eventually resulting in increased Pulmonary Vascular Resistance that causes a shunt reversal from Right to Left instead

Question 8

What are the causes of obstructive CHD?

Answer 8

1. coarctation of the aorta
2. aortic valvular stenosis
3. pulmonary valvular stenosis

Question 9

What are characteristics of VSD?

Answer 9

• defect in septum that divides right and left ventricles
• most common congenital heart defect
• associated with fetal alcohol syndrome

Question 10

What are characteristics of ASD?

Answer 10

• defect in septum that divides right and left atria
• most common type is ostium secundum (90% cases)
• ostium primum is type associated with down syndrome

Question 11

What is a Split S2 sound on auscultation found in ASD?

Answer 11

• Blood shunts left to right: from left atrium → right atrium
  
  • This increases:
  • Right atrial volume
  • Right ventricular volume
  • Blood flow through the pulmonary valve

What is S2?

S2 = second heart sound, made up of:
* A2 = aortic valve closure
* P2 = pulmonary valve closure

In ASD:
* There’s always extra blood on the right side (from L→R shunt)
* This causes persistent delay of P2, even during expiration
* So the split doesn’t vary with breathing = “fixed”
* And it’s wider than normal due to more volume → “wide, fixed split”

Question 12

Why does ASD cause Paradoxical Emboli?

Answer 12

Normally:
* A venous embolus (like from a DVT) travels → right heart → lungs = pulmonary embolism

In ASD with right-to-left shunting (which can happen transiently or with pulmonary hypertension):
1. A venous clot enters the right atrium
2. But instead of going to the lungs, it crosses the ASD to the left atrium
3. Then goes to the systemic circulation → can cause:
* Stroke
* MI
* Limb ischemia

➡️ This is called a paradoxical embolism — because a venous clot causes an arterial event

What triggers it?
* Increased right heart pressure, such as:
* Straining (Valsalva)
* Coughing
* Pulmonary hypertension
* Or a PFO (patent foramen ovale), which behaves similarly to an ASD

Wide, fixed S2
Constant L→R shunt → always extra blood on right → delayed P2 regardless of breathing
Paradoxical embolism
R→L shunting allows venous clot to bypass lungs and enter systemic circulation → stroke or MI

Question 13

What is characteristic of Patent Ductus Arteriosus (PDA)?

Answer 13

• associated with congenital rubella
• blood goes from aorta to pulmonary circulation, this increases volume in RV and pulmonary pressure, eventually leading to increased PVR. This later leads to Right to Left shunt from Pulmonary to Aorta instead which INCREASES lower extremity O2 levels a little bit because the PDA occurs after the subclavian artery
• asymptomatic at birth with holosystolic “machine-like” murmur also known as high pitch blowing murmur (blown through systole)

Question 14

Why is the blood in the pulmonary artery partially oxygenated in reverse shunt of PDA?

Answer 14

Why is cyanosis more prominent in the lower extremities?
* The PDA connects to the descending aorta, which supplies the lower body.
* The upper body (head and arms) get blood from the aortic arch proximal to the PDA, so they receive mostly normal oxygenated blood from the left ventricle.
* But the lower body receives mixed (less oxygenated) blood coming retrograde from the pulmonary artery via PDA → causing cyanosis in the lower extremities only.

Summary:
* Shunt reversal in PDA means blood flows from pulmonary artery → aorta.
* This blood is mixed oxygenated and deoxygenated, not purely deoxygenated.
* The lower body receives this less oxygenated blood, causing cyanosis there.
* The upper body gets normal oxygenated blood, so no cyanosis in the arms or head.

Question 15

What is the treatment of PDA?

Answer 15

• indomethacin
• Prostoglandin synthesis inhibitors
  (We give prostaglandin E1 to keep the PDA open)
• decreased prostoglandin will cause PDA to be closed

Question 16

What are characteristics of Tetrology of Fallot?

Answer 16

• VSD
• Aorta that overrides that VSD
• Right ventricular hypertrophy
• Pulmonary stenosis (stenosis of right ventricular outflow tract)
• greater pulmonary stenosis leads to more blood being shunter to the left side and more cyanosis will occur

Question 17

Why does Squatting help patients with cyanosis in tetrology of fallot?

Answer 17

In Tetralogy of Fallot:
* The right ventricular outflow is obstructed (pulmonary stenosis)
* So blood is diverted through the VSD → aorta (right-to-left shunt)
* This bypasses the lungs → causes cyanosis

Now add squatting:

🦵 Squatting → ↑ systemic vascular resistance (SVR)
* Compresses arteries in the legs → ↑ afterload
* This makes left ventricular pressure rise

💥 What does that do?
* Now the pressure in the left ventricle is higher than in the right ventricle
* This pushes blood back across the VSD from left to right
* Right-to-left shunting decreases
* More blood flows into the lungs via pulmonary circulation
* → Improves oxygenation ✅

Condition
VSD Shunt Direction
Lung Blood Flow
Cyanosis
Without squatting
Right → Left
↓↓
More cyanosis
With squatting
Less R→L, more L→R
↑↑
Less cyanosis

Question 18

What is X-Ray shape for TOF?

Answer 18

• Boot shaped
• marked RV hypertrophy

Question 19

What genetic disease is TOF associated with?

Answer 19

DiGeorge Syndrome – 22q11 deletion syndrome of chromosome 22

Question 20

What is characteristic of Transposition of Great Vessels?

Answer 20

• the pulmonary artery arises from left ventricle and aorta arises from right ventricle
• it is associated with maternal diabetes
• this creates 2 closed circuits that do not mix

Question 21

How does PDA help the Transposition of Great Vessels?

Answer 21

PDA connects the aorta and pulmonary artery, so in TGA:
* It allows mixing of oxygenated and deoxygenated blood
* Some oxygenated blood from the lungs (via pulmonary artery) can go through the PDA → aorta → systemic circulation
* This provides life-sustaining oxygenation to the body

✅ So even though the circuits are “wrong,” the PDA creates a bridge between them.

⸻

🧠 Key Concept:

In TGA, any connection that allows mixing is critical:

*	PDA (aorta ↔ pulmonary artery)
*	ASD (RA ↔ LA)
*	VSD (RV ↔ LV)

🩺 That’s why:
* We give Prostaglandin E1 to keep the ductus arteriosus open right after birth
* And emergency procedures (like balloon atrial septostomy) may be needed if mixing is poor

💡 How does PDA help?
* The PDA connects the pulmonary artery and the aorta
* In TGA, since the pulmonary artery is under higher pressure (from the LV, which is the stronger pump), blood can flow from pulmonary artery → aorta via PDA
* This allows oxygenated blood from the lungs to reach the systemic circulation (hypertrophy of the right ventricle and atrophy of the left ventricle)

This right-to-left shunting via PDA is life-saving in TGA:
* It delivers oxygenated blood from the lungs (pulmonary artery) to the body (aorta)
* Without it, the body would get only deoxygenated blood from the RV–aorta loop

⸻

🔧 Clinical Management
* We give prostaglandin E1 to keep the PDA open (or reopen it)
* We may also perform atrial septostomy to increase mixing of blood
* Definitive treatment = surgical arterial switch

Question 22

What is X-ray sign for Transposition of Great Vessels?

Answer 22

• Egg on a String Sign

Question 23

What is Truncus Arteriosus?

Answer 23

• single large vessel arising from both ventricles causes a mixing of both oxygenated and deoxygenated blood (truncus fails to divide)

Question 24

What is Tricuspid Atresia

Answer 24

• Tricuspid Valve orifice fails to develop
• right Ventricle is hypoplastic
• associated with ASD

🩸 So how does blood leave the right atrium?

It needs an alternative route, which is where the ASD (atrial septal defect) comes in.

⸻

🔁 Why an ASD is Necessary:

Without a tricuspid valve:
* Blood pools in the right atrium
* It needs to cross into the left atrium via an ASD to escape

➡️ So blood flows RA → LA (via ASD)

That’s a right-to-left shunt at the atrial level ✅

🔵 But isn’t that deoxygenated blood?

Yes — this deoxygenated blood from the RA mixes into the LA, then goes:
→ to the LV
→ and out through the aorta to the body

🟣 This leads to cyanosis (blue baby)

⸻

🛠️ What else is usually needed?

In tricuspid atresia, you also typically need:
* An ASD → to allow blood from RA to LA (R→L shunt ✅)
* A VSD → to allow some blood to go from LV → RV → pulmonary artery → lungs
* Or a PDA (patent ductus arteriosus) → to supply blood to the lungs directly from aort

Question 25

What is Coarctation of the Aorta?

Answer 25

- narrowing of the aorta - can be Infantile and Adult forms

Question 26

What is the Infantile form of Coarctation of the Aorta?

Answer 26

- here, the coarctation lies distal to the aortic arch but proximal to the PDA and is associated with a PDA - presents as lower extremity cyanosis in infants because the decreased pressure of blood flow in the aorta after the coarctation causes the blood to flow into the pulmonary trunk instead VIA the PDA, upper extremity does not experience cyanosis because the 3 branches of the aorta are still receiving sufficient blood supply (braciocephalic, common carotid and left subclavian) ** Associated with Turner Syndrome

Question 27

What is the Adult form of Coarctation of the Aorta?

Answer 27

- not associated with a PDA - coarctation lies distal to the aortic arch, but since there is NO PDA, it presents as hypertension in the upper extremities and hypotension with weak pulses in the lower extremities - associated with bicuspid aortic valve - increased turbulence of blood flow over years can lead to focal increased atherosclerosis

Question 28

Why does Coarctation of the Aorta cause notching of the ribs?

Answer 28

- this is due to the collateral circulation that develops across the intercostal arteries becoming enlarged and compressing the surface of the bone (figure 3 shape)

Question 29

Does the progression from a left-to-right shunt to a right-to-left shunt (as in Eisenmenger syndrome) typically cause left ventricular hypertrophy (LVH)?

Question 30

What are Eisenmenger Clues?

Answer 30

* Cyanosis (late) * Clubbing * Polycythemia (↑ RBCs due to low oxygen) * Loud P2 (from high pulmonary pressure) * Signs of right heart failure

Question 31

Is the Volume overload of left atrium and left ventricle because of the shunt reversal from PDA where it goes from pulmonary artery to the aorta?

Answer 31

🛑 NO — The volume overload of the left atrium and left ventricle in PDA happens before shunt reversal — during the initial left-to-right shunt phase, not during the right-to-left phase. ⸻ 🔄 Let’s break it down step-by-step: 🟢 Early PDA (Left → Right Shunt) * Blood flows from aorta → PDA → pulmonary artery * That extra blood goes to the lungs * It then returns to the left atrium, then left ventricle ✅ Result: * ↑ Volume in left atrium and left ventricle * Left-sided volume overload * Can cause LV dilation, bounding pulses, wide pulse pressure ⸻ 🔴 Late PDA (Right → Left Shunt, Eisenmenger phase) * Now pulmonary artery pressure is higher than aortic pressure * Shunt reverses: blood goes from pulmonary artery → aorta * Blood bypasses the lungs, goes straight to systemic circulation ✅ Result: * No more volume overload of the left heart * Instead: right ventricle faces pressure overload * You get cyanosis, especially in the lower limbs (since PDA usually enters distal to the left subclavian artery)

Question 32

What does an Overriding Aorta mean in TOF?

Answer 32

- Aorta is positioned over the VSD, receiving blood from both ventricles

Question 33

Does a paradoxal emboli in ASD only occur once there is reversal in the shunting from left to right to right to left, and that's only after there is hypertension in the pulmonary side?

Answer 33

💥 What is a paradoxical embolism? * Normally, a venous embolus (like from a DVT) travels: vein → right heart → lungs → gets filtered or causes a pulmonary embolism. * A paradoxical embolism is when that venous embolus bypasses the lungs and instead enters the systemic arterial circulation, potentially causing a stroke, MI, or systemic infarction. * For that to happen, there has to be: 1. A right-to-left shunt, and 2. A passage like an ASD (e.g., patent foramen ovale or true ASD). ⸻ ⛔ Why paradoxical emboli don’t normally occur in early ASD: * In a typical ASD, the pressure in the left atrium is higher than the right. * So blood flows left-to-right, meaning no route for a venous embolus to reach the arterial side. * Any clot from a DVT is filtered out by the lungs → pulmonary embolism, not stroke. ⸻ 💨 When paradoxical embolism can happen: 1. Chronic pulmonary hypertension (e.g., Eisenmenger syndrome): * Right atrial pressure rises above left atrial pressure. * The shunt reverses → right-to-left → now a clot can pass through the ASD into systemic circulation. 2. Transient reversal (important nuance): * Even in people with a PFO (patent foramen ovale) and normal pressure, transient events like coughing, Valsalva, or straining can momentarily raise right atrial pressure above left. * This can cause a brief right-to-left shunt, enough for a paradoxical embolus. * This is why some strokes in younger people are linked to PFO without Eisenmenger — it’s not constant shunting, just episodic.

Question 34

How does PDA lead to lower extremity cyanosis?

Answer 34

Yes — a shunt reversal in a patent ductus arteriosus (PDA) absolutely can cause cyanosis, and here’s exactly how and why: ⸻ 🔁 Normal PDA (before reversal): * Left-to-right shunt: Blood flows from the aorta (high pressure) into the pulmonary artery (low pressure). * This means extra oxygenated blood goes to the lungs. * No cyanosis initially, because the systemic circulation is still getting well-oxygenated blood. * But over time, the lungs are overloaded → pulmonary hypertension develops. ⸻ 🔄 Reversed PDA (Eisenmenger physiology): * Pulmonary hypertension eventually causes the pressure in the pulmonary artery to exceed that in the aorta. * Now blood flows from the pulmonary artery → aorta: a right-to-left shunt. ⸻ 🩸 Where does the deoxygenated blood go? It depends on where the PDA connects: * The ductus arteriosus typically connects the pulmonary artery to the descending aorta, after the branches to the head and upper limbs (i.e., distal to the left subclavian artery). * So in shunt reversal, deoxygenated blood from the pulmonary artery enters the descending aorta, mixing with oxygenated systemic blood. ⸻ 🔵 What does that mean clinically? * Cyanosis of the lower body — a phenomenon called differential cyanosis. * Upper body (fed by vessels before the PDA): receives well-oxygenated blood → pink. * Lower body (fed by aorta after the PDA): receives mixed or deoxygenated blood → cyanotic. * This results in: * Normal O2 saturation in arms, but * Lower O2 saturation in legs.

Question 35

What is a Tet spell?

Answer 35

Absolutely — here’s a simple and clear explanation of a Tet spell (also called a hypercyanotic spell), which is a classic feature of Tetralogy of Fallot. ⸻ ❓ What is a Tet spell? A Tet spell is a sudden episode of: * Deep blue or purple skin, lips, and nails (cyanosis) * Rapid breathing * Sometimes fainting or even seizures (in severe cases) It usually happens in infants or young children with unrepaired Tetralogy of Fallot, especially during: * Crying * Feeding * Playing * Straining or pooping ⸻ 🧠 What causes a Tet spell? It’s due to a sudden increase in right-to-left shunting through the VSD. Here’s how it works: 1. The narrowed pulmonary outflow (pulmonary stenosis) already limits blood flow to the lungs. 2. During stress (crying, etc.), the muscles in the right ventricle or around the pulmonary valve can spasm — making the outflow even narrower. 3. Now, even more deoxygenated blood is forced through the VSD into the aorta → less goes to lungs, and more unoxygenated blood reaches the body. 4. Result: sudden worsening of cyanosis, low oxygen levels → Tet spell. ⸻ 🚨 What does a Tet spell look like? * Sudden cyanosis * Irritability or crying * Rapid breathing (trying to get more oxygen) * May pass out if it’s bad enough✅ Simple summary: A Tet spell is a sudden drop in oxygen levels due to more deoxygenated blood bypassing the lungs. It’s an emergency that needs immediate intervention, and long-term it’s prevented by surgical repair of Tetralogy of Fallot.

Question 36

Explain Overriding Aorta in TOF?

Answer 36

🫀 What does “overriding aorta” mean in Tetralogy of Fallot? Normally, the aorta comes entirely off the left ventricle — so it gets only oxygenated blood. But in Tetralogy of Fallot, the aorta is “overriding” the ventricular septal defect (VSD) — meaning: 👉 The aorta is positioned right over the hole between the left and right ventricles (the VSD). 👉 So instead of just getting blood from the left ventricle, it now receives blood from both ventricles — oxygenated and deoxygenated blood. ⸻ 🚨 What does this cause? Because of the other problems in Tetralogy of Fallot — especially right ventricular outflow obstruction (pulmonary stenosis) — the pressure in the right ventricle is high, so: ➡️ Deoxygenated blood from the right ventricle crosses the VSD and goes into the aorta ➡️ The body gets mixed blood — less oxygen than normal ➡️ This causes cyanosis (blue skin/lips), especially during exertion ⸻ ✅ Simple summary: Overriding aorta means the aorta sits over the hole between the ventricles, so it pulls in blood from both sides — not just the oxygen-rich side. As a result, the body gets less oxygenated blood, causing cyanosis in Tetralogy of Fallot.