FE FE Cardiac Biometry & Measurements 2 — Questions and Answers
Question 1: The myocardial performance index (MPI, Tei index) is calculated using which formula?
- (ICT + IRT) / ET (Correct answer)
- ET / (ICT + IRT)
- ICT / (IRT + ET)
- (ET + IRT) / ICT
Correct answer: (ICT + IRT) / ET
MPI = (isovolumetric contraction time + isovolumetric relaxation time) / ejection time; a higher value indicates worse global ventricular function.
Question 2: The normal fetal left ventricular myocardial performance index (MPI) is approximately:
- Less than 0.20
- 0.30–0.45 (Correct answer)
- 0.50–0.65
- Greater than 0.70
Correct answer: 0.30–0.45
Normal fetal LV MPI is approximately 0.36 ± 0.06, placing the expected range at roughly 0.30–0.45; values above 0.50 suggest ventricular dysfunction.
Question 3: In early second-trimester fetuses, the mitral and tricuspid valve E/A ratio is typically:
- Greater than 1.0 (passive filling dominates)
- Exactly 1.0
- Less than 1.0 (atrial contraction wave dominates) (Correct answer)
- Not measurable before 24 weeks
Correct answer: Less than 1.0 (atrial contraction wave dominates)
In early gestation the fetal myocardium is relatively stiff, so passive (E wave) filling is less than active atrial contraction (A wave), giving an E/A ratio less than 1.0 that gradually increases toward term.
Question 4: Which Doppler measurement at the aortic isthmus best reflects the balance between cerebral and placental vascular resistance?
- Peak systolic velocity
- Pulsatility index (PI) (Correct answer)
- End-diastolic velocity alone
- Time-averaged mean velocity
Correct answer: Pulsatility index (PI)
The aortic isthmus pulsatility index reflects the impedance balance between cerebrovascular (downstream of the arch) and uteroplacental (downstream of the ductus) circuits, making it a sensitive marker of fetal redistribution.
Question 5: The ductus venosus pulsatility index for veins (PIV) is calculated as:
- (S − a) / TAMXV (Correct answer)
- (S − D) / TAMXV
- (S − a) / D
- S / (D + a)
Correct answer: (S − a) / TAMXV
DV PIV = (peak systolic velocity S minus atrial contraction nadir a) divided by time-averaged maximum velocity (TAMXV), capturing the full pulsatility range.
Question 6: In a healthy fetus, the Doppler waveform at the ductus venosus during atrial contraction (a-wave) should be:
- Absent (zero flow)
- Reversed (retrograde)
- Forward (positive) flow (Correct answer)
- Biphasic with brief reversal
Correct answer: Forward (positive) flow
A normal ductus venosus maintains forward (anterograde) flow throughout the cardiac cycle including atrial contraction; a-wave reversal indicates elevated right atrial pressure and fetal compromise.
Question 7: Under normal circumstances, blood flow at the aortic isthmus (AoI) during diastole should be:
- Absent (zero net flow)
- Retrograde (reversed)
- Anterograde (forward) (Correct answer)
- Bidirectional and equal
Correct answer: Anterograde (forward)
In a normally grown fetus with balanced cerebrovascular and uteroplacental resistance, aortic isthmus flow is anterograde throughout the cardiac cycle including diastole; diastolic reversal signals placental insufficiency or brain redistribution.
FE FE Cardiac Biometry & Measurements 2
The myocardial performance index (MPI, Tei index) is calculated using which formula?