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Question 1Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Which fetal vessel carries oxygenated blood from the placenta to the fetus?

  1. Umbilical artery
  2. Umbilical vein Correct answer.
  3. Descending aorta
  4. Ductus arteriosus

Explanation

The umbilical vein carries oxygen-rich blood from the placenta toward the fetal liver and ductus venosus. The umbilical arteries return deoxygenated blood from the fetus to the placenta.

Question 2Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Which structure provides the normal right-to-left atrial shunt in the fetus?

  1. Ductus arteriosus
  2. Ostium primum
  3. Foramen ovale Correct answer.
  4. Ductus venosus

Explanation

The foramen ovale is the physiologic right-to-left communication between the fetal atria. It is formed by the overlapping septum primum and septum secundum.

Question 3Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The ductus arteriosus normally connects which two structures?

  1. Pulmonary veins to left atrium
  2. Main pulmonary artery to descending aorta Correct answer.
  3. Right ventricle to ascending aorta
  4. Superior vena cava to right atrium

Explanation

The ductus arteriosus shunts blood from the main pulmonary artery to the descending aorta, bypassing the high-resistance fetal lungs. After birth it constricts and becomes the ligamentum arteriosum.

Question 4Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Which vessels carry deoxygenated blood from the fetus to the placenta?

  1. Ductus venosus
  2. Portal vein
  3. Umbilical artery Correct answer.
  4. Umbilical vein

Explanation

The umbilical arteries arise from the internal iliac arteries and carry deoxygenated blood and waste products from the fetus to the placenta. The umbilical vein carries oxygenated blood in the opposite direction.

Question 5Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In the normal fetus, which chamber ejects the larger proportion of combined ventricular output?

  1. Left ventricle
  2. The two ventricles are equal
  3. Left atrium
  4. Right ventricle Correct answer.

Explanation

The fetal right ventricle ejects about 60% of combined ventricular output because the ductus arteriosus offers a low-resistance outlet. The left ventricle supplies the ascending aorta and cerebral circulation.

Question 6Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The ductus venosus connects the umbilical vein to which structure?

  1. Aorta
  2. Inferior vena cava Correct answer.
  3. Right atrium
  4. Portal vein

Explanation

The ductus venosus connects the intra-abdominal umbilical vein to the inferior vena cava, allowing oxygenated blood to bypass the liver. It becomes the ligamentum venosum after birth.

Question 7Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Functional closure of the foramen ovale after birth is primarily caused by which change?

  1. An increase in umbilical venous return
  2. Closure of the ductus arteriosus
  3. A fall in pulmonary vascular resistance with a rise in left atrial pressure Correct answer.
  4. A rise in right atrial pressure

Explanation

After birth, lung expansion lowers pulmonary vascular resistance and increases pulmonary venous return to the left atrium. The resulting rise in left atrial pressure presses septum primum against septum secundum and closes the foramen ovale.

Question 8Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The obliterated intra-abdominal umbilical vein becomes which postnatal structure?

  1. Ligamentum venosum
  2. Medial umbilical ligament
  3. Ligamentum arteriosum
  4. Ligamentum teres Correct answer.

Explanation

The intra-abdominal umbilical vein fibroses after birth and becomes the ligamentum teres, or round ligament of the liver. The ductus venosus becomes the ligamentum venosum.

Question 9Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The embryonic heart begins to beat at approximately which time after conception?

  1. 22 days Correct answer.
  2. 14 days
  3. 56 days
  4. 35 days

Explanation

The primitive heart tube begins rhythmic contractions at approximately 22 days after conception. This corresponds to roughly the beginning of the fifth week of menstrual age.

Question 10Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The membranous portion of the ventricular septum is derived mainly from which tissue?

  1. Endocardial cushion tissue Correct answer.
  2. Bulboventricular flange
  3. Septum primum
  4. Sinus venosus

Explanation

The membranous ventricular septum forms from fused endocardial cushion tissue and the conus septum, which close the interventricular foramen. The muscular septum develops separately from ventricular trabeculation.

Question 11Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Which structure forms the flap-like valve of the foramen ovale?

  1. Eustachian valve
  2. Septum spurium
  3. Septum primum Correct answer.
  4. Septum secundum

Explanation

Septum primum forms the thin, flap-like valve of the foramen ovale, which is pressed against septum secundum after birth. Septum secundum forms the firmer limbus and rim.

Question 12Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The left fourth pharyngeal arch gives rise to which structure?

  1. Arch of the aorta Correct answer.
  2. Common carotid artery
  3. Ductus arteriosus
  4. Facial artery

Explanation

The left fourth pharyngeal arch becomes the arch of the aorta, while the right fourth arch forms the proximal right subclavian artery. The sixth arches give rise to the pulmonary arteries and ductus arteriosus.

Question 13Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The ductus arteriosus is derived from which pharyngeal arch?

  1. Second aortic arch
  2. Left fourth aortic arch
  3. Left sixth aortic arch Correct answer.
  4. Third aortic arch

Explanation

The ductus arteriosus arises from the distal left sixth pharyngeal arch. The third arch forms the common carotid artery and the fourth arch forms the aortic arch.

Question 14Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In the normal fetus, which vessel contains blood with the highest oxygen saturation?

  1. Descending aorta
  2. Main pulmonary artery
  3. Umbilical vein Correct answer.
  4. Superior vena cava

Explanation

The umbilical vein carries the most highly oxygenated fetal blood, with saturation typically around 80-90%. Blood in the descending aorta and pulmonary artery is more mixed and less saturated.

Question 15Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Which change most directly lowers pulmonary vascular resistance at birth?

  1. Lung expansion with an increase in alveolar oxygen Correct answer.
  2. Increased carbon dioxide tension
  3. Closure of the ductus venosus
  4. An increase in hematocrit

Explanation

At birth, air expansion and rising alveolar oxygen cause pulmonary vasodilation and a rapid fall in pulmonary vascular resistance. This permits the large increase in pulmonary blood flow required for extrauterine gas exchange.

Question 16Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Functional closure of the ductus arteriosus usually occurs within which time after birth?

  1. 24-48 hours Correct answer.
  2. 3-4 weeks
  3. 6 months
  4. 7-10 days

Explanation

Functional closure of the ductus arteriosus usually occurs within the first 24-48 hours after birth as oxygen tension rises and prostaglandin E2 levels fall. Anatomical obliteration follows over several weeks.

Question 17Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In normal fetal situs solitus, which arrangement is expected?

  1. Stomach right, cardiac apex right
  2. Stomach left, cardiac apex right
  3. Stomach left, cardiac apex left Correct answer.
  4. Stomach right, cardiac apex left

Explanation

In situs solitus, the stomach and cardiac apex are both on the left. This concordant arrangement represents normal visceral and cardiac position.

Question 18Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The pulmonary veins normally drain into which cardiac chamber?

  1. Right ventricle
  2. Coronary sinus
  3. Right atrium
  4. Left atrium Correct answer.

Explanation

The four pulmonary veins normally drain into the left atrium. In the fetus, pulmonary venous return is small because pulmonary blood flow is low.

Question 19Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In the normal fetal heart, the main pulmonary artery lies in which relationship to the ascending aorta?

  1. Posterior and to the right of the ascending aorta
  2. To the right and posterior to the ascending aorta
  3. Directly posterior to the ascending aorta
  4. Anterior and to the left of the ascending aorta Correct answer.

Explanation

Normally the main pulmonary artery is anterior and to the left of the ascending aorta, and the great vessels cross. Loss of this relationship suggests transposition or another conotruncal abnormality.

Question 20Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The coronary sinus drains directly into which chamber?

  1. Left atrium
  2. Left ventricle
  3. Right ventricle
  4. Right atrium Correct answer.

Explanation

The coronary sinus receives most of the cardiac venous blood and drains into the right atrium near the inferior vena cava. It is not part of the pulmonary venous system.

Question 21Normal Fetal and Pediatric Cardiac Anatomy and Physiology

A normal ductus venosus Doppler waveform in the fetus is characterized by which pattern?

  1. Continuous forward flow with an a-wave during atrial systole Correct answer.
  2. Biphasic flow with absent diastolic forward flow
  3. Reversed flow during atrial systole
  4. Bidirectional pulsatile flow

Explanation

A normal ductus venosus tracing shows continuous forward flow throughout the cardiac cycle, including a forward a-wave during atrial systole. Absent or reversed a-wave flow is abnormal and suggests increased atrial pressure or impaired myocardial function.

Question 22Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In the normal human fetus, the right ventricle contributes approximately what percentage of combined ventricular output?

  1. About 80%
  2. About 45%
  3. About 60% Correct answer.
  4. About 30%

Explanation

The right ventricle handles about 60% of combined ventricular output in the normal fetus because the ductus arteriosus provides a low-resistance outlet to the descending aorta. The left ventricle supplies the upper body and coronary circulation.

Question 23Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Combined ventricular output in mid-gestation is approximately which value?

  1. 800 mL/kg/min
  2. 100 mL/kg/min
  3. 450 mL/kg/min Correct answer.
  4. 200 mL/kg/min

Explanation

Combined ventricular output in mid-gestation is approximately 450 mL/kg/min, reflecting the high metabolic demands of the growing fetus. It is considerably higher per kilogram than adult cardiac output.

Question 24Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Which statement best describes normal flow across the fetal foramen ovale?

  1. Predominantly right-to-left throughout gestation Correct answer.
  2. Predominantly left-to-right throughout gestation
  3. Bidirectional with a net left-to-right direction
  4. Right-to-left only during the first trimester

Explanation

The foramen ovale permits predominantly right-to-left flow throughout gestation because right atrial pressure exceeds left atrial pressure. This directs oxygenated inferior vena caval blood into the left atrium and then to the brain.

Question 25Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Which factor is the principal stimulus for constriction of the ductus arteriosus after birth?

  1. An increase in circulating prostaglandin E2
  2. An increase in pulmonary blood flow
  3. A rise in arterial oxygen tension Correct answer.
  4. A decrease in systemic vascular resistance

Explanation

A rise in arterial oxygen tension after birth is the principal stimulus for ductal constriction. Falling prostaglandin E2 levels then permit anatomical closure of the ductus arteriosus.

Question 26Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In the normal fetal circulation, the ductus arteriosus directly connects which two structures?

  1. Main pulmonary artery and descending aorta Correct answer.
  2. Left pulmonary artery and left atrium
  3. Ascending aorta and main pulmonary artery
  4. Right ventricle and descending aorta

Explanation

The ductus arteriosus is a muscular shunt joining the main pulmonary artery (near its bifurcation) to the descending aorta just distal to the left subclavian artery. It allows most right ventricular output to bypass the high-resistance pulmonary circulation and reach the systemic and placental beds.

Question 27Normal Fetal and Pediatric Cardiac Anatomy and Physiology

A normal term umbilical cord contains how many umbilical arteries?

  1. Two Correct answer.
  2. Four
  3. One
  4. Three

Explanation

The normal cord contains two umbilical arteries and one umbilical vein within Wharton jelly. The arteries arise from the internal iliac arteries and return deoxygenated blood from the fetus to the placenta.

Question 28Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Pulmonary blood flow is low in the normal fetus mainly because of which condition?

  1. A restrictive foramen ovale
  2. High left atrial pressure
  3. High pulmonary vascular resistance Correct answer.
  4. A low fetal heart rate

Explanation

The fetal lungs are fluid filled and the pulmonary arterioles are constricted in the low-oxygen environment, so pulmonary vascular resistance is very high. As a result, only a minority of combined ventricular output perfuses the lungs, and most right ventricular blood is diverted through the ductus arteriosus.

Question 29Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The normal baseline fetal heart rate at term ranges between which values?

  1. 60 and 100 beats per minute
  2. 160 and 200 beats per minute
  3. 110 and 160 beats per minute Correct answer.
  4. 90 and 110 beats per minute

Explanation

The accepted normal baseline fetal heart rate at term is 110 to 160 beats per minute. Rates persistently below 110 define bradycardia and rates above 160 define tachycardia.

Question 30Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Fetal hemoglobin supports fetal oxygenation mainly through which property?

  1. A higher 2,3-diphosphoglycerate concentration than adult red cells
  2. A lower oxygen affinity that favors tissue unloading
  3. A left-shifted oxygen dissociation curve Correct answer.
  4. More oxygen-binding sites per molecule than adult hemoglobin

Explanation

Fetal hemoglobin binds 2,3-diphosphoglycerate poorly, so its oxygen dissociation curve is shifted left relative to adult hemoglobin. This gives it a higher oxygen affinity, allowing uptake of oxygen across the placenta at relatively low partial pressures.

Question 31Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In infants, cardiac output is increased mainly by which mechanism, reflecting immature myocardial properties?

  1. Reduced afterload through systemic vasodilation
  2. A large increase in stroke volume through the Frank-Starling mechanism
  3. An increase in heart rate Correct answer.
  4. Greater calcium release from a well-developed sarcoplasmic reticulum

Explanation

The infant myocardium is less compliant and has a limited capacity to augment stroke volume, so the Frank-Starling reserve is small. Cardiac output therefore rises predominantly through increases in heart rate.

Question 32Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In the fetus, which structure preferentially directs blood from the inferior vena cava toward the interatrial septum?

  1. The eustachian valve Correct answer.
  2. The septomarginal trabeculation
  3. The crista terminalis
  4. The thebesian valve

Explanation

The eustachian valve (valve of the inferior vena cava) is a ridge at the junction of the inferior vena cava and right atrium that streams the well-oxygenated caval blood toward the foramen ovale. This streaming preferentially loads the left atrium and left ventricle with the most oxygenated blood.

Question 33Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Which electrocardiographic finding is normal in a healthy newborn during the first week of life?

  1. A completely upright T wave in V1
  2. Left axis deviation with left ventricular dominance
  3. Right axis deviation with right ventricular dominance Correct answer.
  4. A QT interval longer than 0.50 seconds

Explanation

Because the fetal right ventricle works against systemic pressure, it is relatively thick at birth, producing right axis deviation and dominant right ventricular forces on the neonatal ECG. These features regress over the first months as left ventricular mass increases.

Question 34Normal Fetal and Pediatric Cardiac Anatomy and Physiology

What is the approximate normal resting heart rate for a healthy 5-year-old child?

  1. 80 to 110 beats per minute Correct answer.
  2. 40 to 60 beats per minute
  3. 60 to 75 beats per minute
  4. 120 to 160 beats per minute

Explanation

Resting heart rate declines with age: it averages roughly 120 to 140 beats per minute in infancy and falls to about 80 to 110 beats per minute by early school age. Rates in the adult range are usually not reached until adolescence.

Question 35Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In the normal fetus at mid-gestation, which great vessel is the largest?

  1. The ascending aorta
  2. The superior vena cava
  3. The aortic isthmus
  4. The main pulmonary artery Correct answer.

Explanation

Because the right ventricle handles the larger share of combined ventricular output in fetal life, the main pulmonary artery is slightly larger than the ascending aorta. This relationship reverses after birth as pulmonary vascular resistance falls and left ventricular output increases.

Question 36Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Compared with adult myocardium, normal fetal myocardium depends more on which factor for contraction?

  1. Intracellular calcium release from a well-developed sarcoplasmic reticulum
  2. High compliance permitting large stroke volume increases
  3. High resting sympathetic tone
  4. Extracellular calcium entering through sarcolemmal channels Correct answer.

Explanation

The fetal and neonatal sarcoplasmic reticulum is sparse and immature, so contraction relies heavily on calcium entering across the sarcolemma during the action potential. This makes the immature heart particularly sensitive to changes in extracellular calcium and to calcium-channel blockade.

Question 37Normal Fetal and Pediatric Cardiac Anatomy and Physiology

Blood in the fetal ascending aorta has an oxygen saturation of approximately which value?

  1. 65% Correct answer.
  2. 95%
  3. 80%
  4. 45%

Explanation

Well-oxygenated blood from the ductus venosus streams across the foramen ovale to the left heart, but mixing with pulmonary and caval return means ascending aortic blood is only about 65% saturated. This blood supplies the coronary and cerebral circulations, which are the most oxygen-dependent beds.

Question 38Normal Fetal and Pediatric Cardiac Anatomy and Physiology

The normal fetal cardiac axis measured in the four-chamber view is approximately which value?

  1. About 45 degrees to the left of the midline Correct answer.
  2. About 45 degrees to the right of the midline
  3. About 90 degrees to the right of the midline
  4. Zero degrees, aligned with the midline

Explanation

In normal levocardia the cardiac apex points to the left, and the axis measured from the anterior midline is approximately 45 degrees to the left. Marked deviation, particularly to the right, raises concern for conotruncal or other structural anomalies.

Question 39Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In a healthy term newborn, pulmonary vascular resistance approaches adult values at approximately what age?

  1. By 12 months
  2. By 5 years
  3. By 6 to 8 weeks Correct answer.
  4. Within the first 24 hours

Explanation

Pulmonary vascular resistance falls abruptly with lung inflation and rising oxygen tension at birth, but the medial smooth muscle of the pulmonary arterioles regresses more slowly. Adult-level resistance is generally reached by about 6 to 8 weeks of life.

Question 40Normal Fetal and Pediatric Cardiac Anatomy and Physiology

In the first hours after birth, before the ductus arteriosus closes, flow through the vessel typically changes in which way?

  1. It stops abruptly at the first breath
  2. It remains exclusively right-to-left
  3. From left-to-right to right-to-left
  4. From right-to-left to predominantly left-to-right Correct answer.

Explanation

At birth, pulmonary vascular resistance falls and pulmonary blood flow rises, so the pressure gradient across the ductus reverses. Flow therefore becomes bidirectional and then predominantly left-to-right (aortic to pulmonary) before functional closure occurs.

Question 41Congenital Heart Disease Pathophysiology and Lesion Classification

The conotruncal septum that divides the embryonic outflow tract into the aorta and pulmonary trunk is derived primarily from which cell population?

  1. Endocardial cushion mesenchyme of the atrioventricular canal
  2. Sclerotome cells of the somites
  3. Splanchnic lateral plate mesoderm
  4. Cardiac neural crest cells Correct answer.

Explanation

Cardiac neural crest cells migrate through pharyngeal arches 3, 4 and 6 and form the aorticopulmonary (conotruncal) septum. Failure of this migration produces conotruncal defects such as truncus arteriosus, tetralogy of Fallot and interrupted aortic arch.

Question 42Congenital Heart Disease Pathophysiology and Lesion Classification

In the fetal circulation, which vessel shunts blood from the pulmonary artery to the descending aorta?

  1. Ductus venosus
  2. Umbilical vein
  3. Ductus arteriosus Correct answer.
  4. Foramen ovale

Explanation

The ductus arteriosus connects the main pulmonary artery to the descending aorta and diverts blood away from the high-resistance fetal lungs. It constricts after birth as oxygen tension rises and prostaglandin E2 levels fall.

Question 43Congenital Heart Disease Pathophysiology and Lesion Classification

Which defect is the most frequently occurring congenital cardiac malformation at birth?

  1. Ventricular septal defect Correct answer.
  2. Atrial septal defect
  3. Tetralogy of Fallot
  4. Patent ductus arteriosus

Explanation

Ventricular septal defect is the most common congenital heart lesion detected at birth, accounting for roughly one third of cases. Many small defects close spontaneously during childhood.

Question 44Congenital Heart Disease Pathophysiology and Lesion Classification

Which of the following is one of the four cardinal features of tetralogy of Fallot?

  1. Right ventricular hypertrophy Correct answer.
  2. Patent ductus arteriosus
  3. Aortic regurgitation
  4. Atrial septal defect

Explanation

The four components are a ventricular septal defect, right ventricular outflow tract obstruction, an overriding aorta and right ventricular hypertrophy. The degree of outflow obstruction determines how much right-to-left shunting and cyanosis develops.

Question 45Congenital Heart Disease Pathophysiology and Lesion Classification

Eisenmenger syndrome refers to which sequence of events?

  1. Failure of the ductus arteriosus to close after birth
  2. Spontaneous closure of a septal defect during the first year of life
  3. Progressive narrowing of the aortic isthmus with hypertension in the upper limbs
  4. Reversal of a left-to-right shunt as pulmonary vascular resistance rises Correct answer.

Explanation

Chronic left-to-right shunting raises pulmonary blood flow and pressure and causes irreversible pulmonary vascular remodeling. Once pulmonary vascular resistance exceeds systemic resistance, the shunt reverses and cyanosis appears.

Question 46Congenital Heart Disease Pathophysiology and Lesion Classification

A newborn with suspected transposition of the great arteries is becoming progressively more cyanotic. Which therapy is given to maintain mixing until definitive repair?

  1. Prostaglandin E1 infusion Correct answer.
  2. Inhaled nitric oxide
  3. Oral propranolol
  4. Indomethacin infusion

Explanation

In transposition the systemic and pulmonary circuits run in parallel, so survival depends on mixing at the atrial, ventricular or ductal level. Prostaglandin E1 keeps the ductus arteriosus open until an atrial septostomy or surgical repair can be performed.

Question 47Congenital Heart Disease Pathophysiology and Lesion Classification

An ostium secundum atrial septal defect lies in which part of the atrial septum?

  1. The muscular inlet septum adjacent to the atrioventricular valves
  2. The central septum at the fossa ovalis Correct answer.
  3. The coronary sinus septum
  4. The upper septum near the superior vena cava

Explanation

Ostium secundum defects result from deficient closure of the fossa ovalis and therefore lie centrally in the atrial septum. Primum defects belong to the atrioventricular septal complex, and sinus venosus defects lie near the caval junctions.

Question 48Congenital Heart Disease Pathophysiology and Lesion Classification

Cyanosis in congenital heart disease is caused most directly by which mechanism?

  1. Reduced systemic oxygen extraction by the tissues
  2. Elevated left atrial pressure with pulmonary edema
  3. Increased pulmonary blood flow from a left-to-right shunt
  4. Right-to-left shunting into the systemic circulation Correct answer.

Explanation

Cyanosis appears when desaturated blood enters the systemic circulation, usually through a right-to-left shunt, raising reduced hemoglobin above roughly 5 g/dL. Left-to-right shunts raise pulmonary blood flow but do not lower systemic arterial saturation.

Question 49Congenital Heart Disease Pathophysiology and Lesion Classification

Cardiac catheterization in a child with a large ventricular septal defect shows systemic arterial saturation 95%, mixed venous saturation 75%, pulmonary venous saturation 98% and pulmonary arterial saturation 88%. What is the pulmonary-to-systemic blood flow ratio (Qp/Qs)?

  1. 2.0 Correct answer.
  2. 3.0
  3. 1.5
  4. 1.2

Explanation

Qp/Qs is derived from oximetric saturations as (systemic arterial O2 sat − mixed venous O2 sat) divided by (pulmonary venous O2 sat − pulmonary arterial O2 sat). Here (95 − 75) / (98 − 88) = 20/10 = 2.0, so pulmonary blood flow is twice systemic flow.

Question 50Congenital Heart Disease Pathophysiology and Lesion Classification

A child with a large atrial septal defect is most likely to show which finding on cardiac examination?

  1. Fixed splitting of the second heart sound Correct answer.
  2. A harsh holosystolic murmur at the left sternal border
  3. An early diastolic decrescendo murmur at the left sternal edge
  4. A continuous machinery murmur below the left clavicle

Explanation

The left-to-right atrial shunt increases right ventricular stroke volume, delaying pulmonary valve closure and abolishing the normal respiratory variation in splitting of the second sound. The accompanying flow murmur is a soft ejection murmur at the left upper sternal border.