Fetal Circulation and Color Doppler Lecture Notes

Vocabulary flashcards covering fetal circulatory pathways, Doppler waveform characteristics, and diagnostic clues for valve stenosis and regurgitation.

Umbilical Vein Physiologic Flow

Carries oxygenated blood from the placenta toward the fetal heart in a cephalad direction.

Ductus Venosus

A vessel connecting the umbilical vein to the inferior vena cava (IVC), typically showing flow toward the heart in a sagittal abdomen view.

Foramen Ovale Route

The high-oxygen systemic priority stream where blood flows from the Right Atrium (RA) to the Left Atrium (LA) across the atrial septum.

Pulmonary Bypass Route

A pathway where blood flows from the Right Ventricle (RV) to the Pulmonary Artery (PA), then through the Ductus Arteriosus (DA) to the Descending Aorta, bypassing high-resistance lungs.

Left Brachiocephalic Vein (LBCV) Flow

Moves horizontally across the upper mediastinum, carrying blood from the left side of the head and arm across the midline into the Superior Vena Cava (SVC).

E wave

Represents early diastolic ventricular filling in the biphasic Doppler wave pattern of the mitral and tricuspid valves.

A wave

Represents late diastolic ventricular filling in the biphasic Doppler wave pattern of the mitral and tricuspid valves.

S wave (Mitral/Aortic connection)

A wave representing aortic flow that appears in the opposite direction of mitral flow on Doppler due to the connection between the valves.

Fetal E/A Ratio

In fetal life, the early ventricular filling is always less than late filling, resulting in a ratio less than $1$ until term.

Right Heart Predominance

Reflected in fetal circulation by tricuspid valve velocities being typically higher than mitral valve velocities.

Ductus Venosus Waveform

A triphasic, continuous forward flow pattern with three peaks: S (ventricular systolic contraction), D (early ventricular diastole), and A (atrial contraction).

Normal Great Artery PSV

The normal Peak Systolic Velocity for the Aorta and Pulmonary Artery ranges from $60-80\,cm/s$, with values rising as gestational age increases.

Valvular Stenosis

Narrowing at the valve orifice characterized by color aliasing at the valve tips, thickened/domed leaflets, and the highest PSV at the valve plane.

Supravalvular Stenosis

Narrowing just distal to the valve (ascending aorta or main PA) where the highest PSV is located just beyond the valve plane and leaflets appear to open normally.

Subvalvular Stenosis

Narrowing proximal to the valve in the outflow tract (LVOT or RVOT) showing aliasing below the valve and high PSV before the valve plane.

Significant Inflow Obstruction Clue

A Peak Systolic Velocity $\ge 100\,cm/s$ ($\ge 1.0\,m/s$) at the inflow valves (Mitral/Tricuspid).

Significant Outflow Stenosis Clue

A Peak Systolic Velocity $\ge 150-200\,cm/s$ at the Aortic or Pulmonary valves.

Critical Aortic Stenosis (2D Appearance)

Characterized by a thickened or dysplastic aortic valve and possible left ventricular hypertrophy.

Pulmonary Regurgitation Doppler Clue

Diastolic backward flow into the Right Ventricle (RV) visualized on color Doppler.

Tricuspid Regurgitation (TR) and Chromosomal Abnormalities

TR is present in approximately $55\%$ of fetuses affected by Trisomy 21 and $33\%$ of those with Trisomy 18 or 13.

High PRF Setting

Indicated for evaluating Atrioventricular (AV) valves, typically set between $>45-70\,cm/sec$.

Low PRF Setting

Indicated for evaluating pulmonary and caval veins or small vessels, typically set at $<20\,cm/sec$.