FE Cardiac Biometry & Measurements Flashcards

What is the normal cardiothoracic area ratio (CTR) in a normal fetus on the four-chamber view?

Answer: Less than 0.33 (approximately 1/3 of thoracic area)

The fetal heart normally occupies less than one-third of the thoracic cross-sectional area, giving a cardiothoracic area ratio of less than 0.33.

The normal fetal cardiac axis (angle of the interventricular septum relative to the anterior-posterior midline) is approximately:

Answer: 45° ± 20° to the left

Normal fetal cardiac axis is approximately 45° ± 20° to the left of the midline (range 25–65°); deviation outside this range warrants further evaluation.

In fetal cardiac biometry, z-scores normalize measurements primarily against which parameter?

Answer: Estimated fetal weight or gestational age

Z-scores express how many standard deviations a measurement is from the mean for a given estimated fetal weight or gestational age, allowing size-independent comparison.

The mitral and tricuspid valve annulus diameters are most accurately measured in which view and at which phase of the cardiac cycle?

Answer: Four-chamber view at end-diastole

Atrioventricular valve annuli are measured in the four-chamber view at end-diastole (maximal opening), which provides the most reproducible and clinically relevant dimension.

When measuring the aortic valve annulus by fetal echocardiography, the standard technique is:

Answer: Peak systole, inner edge to inner edge

Semilunar valve annuli (aortic and pulmonary) are measured at peak systole using inner-edge to inner-edge technique, when the leaflets are maximally open.

In normal fetal circulation, the main pulmonary artery (MPA) to aorta (Ao) diameter ratio is approximately:

Answer: 1.1–1.3 (pulmonary artery slightly larger)

The fetal MPA is normally slightly larger than the aorta (ratio ~1.1–1.3) because the right ventricle carries the higher combined ventricular output through the ductus arteriosus.

What is the expected right ventricular (RV) to left ventricular (LV) size relationship in a normal fetus on the four-chamber view?

Answer: Approximately equal, with the RV mildly dominant (RV:LV ≈ 1.0–1.1)

In fetal life the two ventricles are approximately equal in size with mild right-sided dominance (RV:LV ≈ 1.0–1.1) because the RV ejects the majority of the combined cardiac output.