PEDS Cardio

Why does the left atrium have higher pressure than the right atrium after birth?

Because once the lungs expand, pulmonary vascular resistance drops and pulmonary venous return increases, raising left‑sided pressures.

Why does the left ventricle have higher pressure than the right ventricle?

The LV pumps to systemic circulation, which has much higher resistance than the pulmonary circuit.

What is the purpose of the foramen ovale in fetal circulation?

It allows blood to bypass the lungs by shunting from the RA → LA, sending ~2/3 of fetal blood to the systemic circulation.

What happens to the remaining 1/3 of fetal blood that enters the RV?

It goes toward the pulmonic valve but is diverted through the ductus arteriosus into the aorta, bypassing the lungs.

Why must the foramen ovale and ductus arteriosus close after birth?

The newborn must oxygenate blood independently, so fetal shunts must close to establish normal pulmonary circulation.

When should the ductus arteriosus close, and when is it concerning?

Functionally by ~15 hours

What triggers closure of the ductus arteriosus?

The first breath increases oxygen tension and raises left‑sided pressures, promoting closure.

Why might clinicians intentionally keep the ductus arteriosus or foramen ovale open?

To maintain critical blood flow in certain congenital heart defects until surgery can be performed.

Why is a venous hum heard more on the right side?

Because it reflects venous return, which is greater on the right.

When does the septum primum begin to grow toward the endocardial cushion?

Around 7–10 weeks of gestation.

What is the first structure that begins forming the atrial septum?

The septum primum, which grows downward toward the endocardial cushion.

What is the ostium primum?

The initial gap between the descending septum primum and the endocardial cushion.

What happens once the septum primum reaches the endocardial cushion?

The ostium primum closes, and small perforations appear in the upper septum primum.

How does the ostium secundum form?

The tiny perforations in the septum primum merge into one larger opening called the ostium secundum.

What is the role of the septum secundum in atrial septal development?

It forms to the right of the septum primum and creates a flap‑like tunnel over the ostium secundum.

How does the foramen ovale form?

From the relationship between the septum primum, septum secundum, and endocardial cushion, creating a flap‑like opening.

Why is the foramen ovale a one‑way valve in fetal life?

Because the septum primum acts as a flexible flap that opens with higher right‑sided pressure and closes against the septum secundum when left‑sided pressure rises.

What causes the foramen ovale to close after birth?

Left‑sided pressure becomes higher than right‑sided pressure, pushing the septum primum shut against the septum secundum.

What happens if the septum primum and septum secundum do not overlap correctly?

A persistent opening remains, leading to an atrial septal defect.

How does chronic atrial enlargement affect arrhythmia risk?

Persistent atrial enlargement increases the risk of atrial fibrillation.

What produces S1?

Closure of the mitral and tricuspid valves at the start of systole.

What produces S2?

Closure of the aortic and pulmonic valves at the start of diastole.

Why is bicuspid aortic valve associated with aortic narrowing?

Because the aorta and aortic valve develop together

Why give prostaglandins in suspected coarctation diagnosed before birth?

To keep the PDA open, reducing volume overload and maintaining systemic perfusion until surgery.

What causes rib notching in coarctation of the aorta?

Enlarged collateral arteries eroding the ribs due to high pressure (functionally like tiny aneurysms).

What is the figure 3 sign?

A radiographic contour caused by pre‑ and post‑stenotic dilation around the narrowed segment of the aorta.

Where is the aorta typically narrowed in coarctation?

At the proximal descending aorta, near the back and axilla.

Why is Tetralogy of Fallot the most common cyanotic congenital heart disease?

Because it includes a VSD, which is the most common congenital heart defect overall.

Do all cyanotic congenital heart diseases require surgery?

Yes, all cyanotic lesions require surgical correction.

Why give prostaglandins at birth in known cyanotic defects?

To keep the ductus arteriosus open and maintain systemic or pulmonary blood flow until surgery.

How does Tetralogy of Fallot affect the cardiac apex?

The apex becomes more horizontal due to RV hypertrophy.

What is limbic sparing?

Redness of the eye that spares the limbus (the white ring around the cornea).

Why give high‑dose aspirin in inflammatory conditions?

High‑dose ASA provides anti‑inflammatory effects.

What is low‑dose aspirin used for?

Anti‑platelet effects.

Why does the foramen ovale close after birth but stay open in utero?

Because fetal right‑sided pressure is higher, keeping the flap open, but after birth left‑sided pressure becomes higher and pushes the septum primum shut.

Why does the ductus arteriosus shunt blood away from the lungs in fetal life?

Because fetal pulmonary vascular resistance is extremely high, so blood prefers the low‑resistance path through the ductus into the aorta.

Why does the LV develop higher pressure than the RV after birth?

Because systemic vascular resistance increases dramatically once the placenta is removed.

Why is it dangerous if the ductus arteriosus stays open beyond 48 hours?

Because persistent left‑to‑right shunting can overload the pulmonary circulation.

Why do some congenital heart defects require keeping the ductus arteriosus open?

Because systemic or pulmonary circulation may depend on ductal flow until surgical repair.

Why is a venous hum louder on the right side?

Because venous return is greater on the right, increasing turbulent flow.

Why does failure of septum primum and septum secundum overlap cause an ASD?

Because the flap‑valve mechanism cannot form without proper alignment.

Why does atrial enlargement increase the risk of atrial fibrillation?

Because stretched atrial tissue disrupts electrical conduction pathways.

Why does the ostium secundum need to form after the ostium primum closes?

To maintain fetal right‑to‑left shunting until birth.

Why does S1 correspond to the start of systole?

Because AV valve closure marks the moment the ventricles begin generating pressure.

Why does S2 correspond to the start of diastole?

Because semilunar valve closure marks the moment ventricular pressure falls below arterial pressure.

Why does bicuspid aortic valve often coexist with aortic narrowing?

Because the valve and aorta develop together, so abnormal development in one affects the other.

Why does coarctation cause rib notching?

Because collateral arteries enlarge to bypass the obstruction and erode the ribs over time.

Why does the figure 3 sign appear on imaging?

Because pre‑stenotic dilation, the narrowed segment, and post‑stenotic dilation create a “3” shape.

Why do infants with coarctation need prostaglandins?

Because keeping the PDA open maintains systemic perfusion until repair.

Why is Tetralogy of Fallot the most common cyanotic heart disease?

Because it includes a VSD, the most common congenital heart defect overall.

Why does the apex become horizontal in Tetralogy of Fallot?

Because RV hypertrophy shifts the heart’s orientation.

Why do all cyanotic lesions require surgery?

Because they involve structural defects that cannot be corrected physiologically.

Why is high‑dose aspirin anti‑inflammatory while low‑dose aspirin is anti‑platelet?

Because higher doses inhibit inflammatory pathways while low doses selectively inhibit platelet aggregation.

Why does limbic sparing help differentiate eye redness causes?

Because sparing of the limbus suggests a benign conjunctival process rather than deeper ocular inflammation.

What type of shunts does normal fetal circulation use?

Right to Left shunts.

How does the fetus receive nutrients and oxygen in normal fetal circulation?

Fetus receives nutrients and oxygen from the placenta.

Where does oxygenation and nutrients go in normal fetal circulation?

Oxygenation and nutrients goes from the placenta to the right atrium.

How many right‑to‑left shunts bypass the fetal lungs?

There are 2 right to left shunts that bypass the fetal lungs.

What does the foramen ovale do in normal fetal circulation?

Shunts about 2/3 blood from right atrium into left atrium.

Where does the remaining 1/3 of blood go from the right atrium in fetal circulation?

Other 1/3 of blood is shunted from right atrium to the right ventricle to the pulmonary artery.

What does the ductus arteriosus do in fetal circulation?

Shunts blood from the pulmonary artery directly to the aorta

What causes closure of fetal shunts after birth?

As baby takes its first breath, left sided pressure becomes higher compared to the right side and ideally closes both openings.

What medication closes fetal shunts?

Prostaglandin inhibitors (IV indomethacin).

What medication keeps fetal shunts patent?

Prostaglandin.

What does and doesn't cause innocent heart murmurs?

Caused by turbulent blood flow, not caused by structural heart disease, and have no hemodynamic significance.

What are the symptoms of innocent murmurs?

Usually asymptomatic.

When do innocent murmurs typically occur?

Typically occurs during systole.

What does a diastolic murmur indicate?

Diastolic murmurs are nearly always pathological.

How common are innocent murmurs in children?

About 50% of children have an innocent murmur at some point during childhood.

What causes a pulmonary flow murmur?

Turbulent flow through a normal pulmonary valve.

What is the epidemiology of pulmonary flow murmurs?

Most common innocent murmur between 8 and 14 years of age.

Where is a pulmonary flow murmur heard?

Mid to upper left sternal border.

What is the sound of a pulmonary flow murmur?

Mid frequency, crescendo decrescendo, systolic.

What are characteristics of a pulmonary flow murmur?

Most common in older children and adults, louder when patient is supine compared to upright.

What causes a Still’s (vibratory) murmur?

Possibly turbulent flow in the left ventricle outflow track region.

What is the epidemiology of Still’s murmur?

Most common between 2 and 7 years of age

Where is a Still’s murmur heard?

Lower left sternal border.

What is the sound of a Still’s murmur?

Musical or vibratory with mid systolic accentuation.

What are characteristics of a Still’s murmur?

Most common innocent murmur, louder supine, may disappear with valsalva, softer during inspiration.

What causes a venous hum?

Turbulent flow of systemic venous return in the jugular veins and superior vena cava.

What is the epidemiology of venous hum?

Most common between three and six years of age.

Where is a venous hum heard?

Infra and supraclavicular, base of neck.

What is the sound of a venous hum?

High frequency, best heard with diaphragm of stethoscope, during systole and diastole, continuous.

What are characteristics of a venous hum?

More prominent on right than left, can be accentuated or eliminated with head position, disappear supine or digital compression of jugular vein, only heard sitting or standing.

What is assessed in the general inspection of the pediatric cardiac PE?

Mental status/distress, perfusion, skin color, vital signs.

Why is BP measured in all four extremities in pediatric cardiac exam?

Worry about coarctation of the aorta.

What is oxygen saturation the best initial screening tool for?

Cyanotic heart defects.

What is the best diagnostic tool for pediatric cardiac evaluation?

ECHO.

What does a precordial bulge suggest?

Cardiomegaly (chronic enlargement).

What does an RV lift/heave indicate?

RV pressure overload (hypertrophy).

What conditions are associated with RV lift/heave?

Pulmonary hypertension, pulmonary stenosis, large VSD.

What does a diffuse PMI indicate?

LV dilation / volume overload.

What does a thrill indicate?

If heard = more than a murmur Grade ≥ IV.

What does a suprasternal thrill suggest?

Aortic stenosis.

What does a palpable P2 indicate?

Pulmonary hypertension.

True or False: Pulmonary hypertension is reversible.

False

What are the general types of congenital heart disorders?

Noncyanotic disorders/acyanotic, cyanotic disorders, hypoplastic left heart syndrome.

What symptoms occur in congenital heart disorders?

Murmur, fatigue, wheezing, pulmonary hypertension, and signs of acute or chronic cyanosis.

What are the two categories of congenital heart disorders?

Noncyanotic and cyanotic.

What do noncyanotic congenital heart disorders involve?

Movement of the blood from the left to the right.