Fetal Cardiac Anatomy & Development Flashcards

Which cardiac defect results from failure of the aortopulmonary septum to spiral normally?

Answer: D-transposition of the great arteries

D-transposition results when the aortopulmonary septum divides the truncus straight rather than spiraling, placing the aorta anterior and rightward over the right ventricle.

By what gestational age can the foramen ovale normally be visualized on fetal echocardiography?

Answer: 14–16 weeks

The foramen ovale and its flap (septum primum) are typically identifiable by 14–16 weeks using transvaginal or transabdominal echocardiography.

The moderator band is a characteristic trabecular structure found in which cardiac chamber?

Answer: Right ventricle

The moderator band is a muscular trabeculation in the right ventricle that carries part of the right bundle branch and helps identify the morphologic right ventricle.

In fetal circulation, what approximate percentage of combined ventricular output is directed through the ductus arteriosus?

Answer: 50–60%

Approximately 50–60% of combined cardiac output crosses the ductus arteriosus because fetal pulmonary vascular resistance is high and very little blood enters the lung circulation.

Which embryonic structure is the origin of the sinus node and contributes to the superior vena cava?

Answer: Sinus venosus

The sinus venosus, the most caudal part of the primitive heart tube, gives rise to the sinus node, the coronary sinus, and incorporates into the posterior right atrium.

Which view best demonstrates the relationship of the pulmonary veins to the left atrium in fetal echocardiography?

Answer: Four-chamber view with posterior angulation

Angling the transducer posteriorly from the four-chamber view allows visualization of pulmonary vein insertion into the posterior left atrium.

What is the normal cardiothoracic ratio (heart area to chest area) in the fetus?

Answer: 0.35–0.60

The normal fetal cardiothoracic ratio ranges from approximately 0.35 to 0.60; values above 0.60 suggest cardiomegaly.