FE FE Arrhythmias & Cardiac Function 2 — Questions and Answers
Question 1: Complete fetal heart block is most strongly associated with which maternal antibody?
- Anti-dsDNA antibodies
- Anti-Ro/SSA and anti-La/SSB antibodies (Correct answer)
- Antiphospholipid antibodies
- Anti-thyroid peroxidase antibodies
Correct answer: Anti-Ro/SSA and anti-La/SSB antibodies
Maternal anti-Ro/SSA and anti-La/SSB antibodies cross the placenta and can damage the fetal AV node, causing congenital complete heart block.
Question 2: In complete heart block, the characteristic echocardiographic finding is:
- 1:1 AV conduction with prolonged PR interval
- Atrial rate higher than ventricular rate with no AV relationship (Correct answer)
- Ventricular rate higher than atrial rate
- Irregular P-wave morphology
Correct answer: Atrial rate higher than ventricular rate with no AV relationship
Complete heart block shows complete AV dissociation with the atrial rate (normal) being faster than the slow ventricular escape rate.
Question 3: Which fetal cardiac condition is most commonly associated with complete heart block in the absence of maternal antibodies?
- Tetralogy of Fallot
- Left atrial isomerism (polysplenia) (Correct answer)
- Ebstein anomaly
- Tricuspid atresia
Correct answer: Left atrial isomerism (polysplenia)
Left atrial isomerism (polysplenia syndrome) is associated with AV nodal abnormalities and is the most common structural cause of congenital complete heart block.
Question 4: Fetal atrial flutter is characterized by:
- Irregular atrial rate of 200–220 bpm
- Regular atrial rate of 300–500 bpm with variable AV conduction (Correct answer)
- Regular ventricular rate matching atrial rate
- Absent P-wave activity
Correct answer: Regular atrial rate of 300–500 bpm with variable AV conduction
Atrial flutter features a rapid, regular atrial rate of 300–500 bpm, typically with 2:1 AV block producing a ventricular rate of 150–250 bpm.
Question 5: Which echocardiographic technique can assess fetal PR interval to detect first- and second-degree heart block?
- B-mode imaging of valve motion
- Tissue Doppler imaging (TDI) of AV valves (Correct answer)
- Color flow mapping
- Pulsed Doppler at the left ventricular outflow tract
Correct answer: Tissue Doppler imaging (TDI) of AV valves
Tissue Doppler imaging can measure the mechanical PR interval by assessing the timing of atrial and ventricular wall motion, enabling detection of AV conduction delays.
Question 6: A fetal heart rate below 100 bpm for more than 10 seconds is defined as:
- Normal variant
- Fetal sinus bradycardia (Correct answer)
- Functional bradycardia
- Supraventricular extrasystole
Correct answer: Fetal sinus bradycardia
Fetal sinus bradycardia is defined as a sustained fetal heart rate below 100 bpm and requires investigation for underlying causes.
FE FE Arrhythmias & Cardiac Function 2
Complete fetal heart block is most strongly associated with which maternal antibody?