Presentation
Monochorial biamniotic pregnancy. No follow up, 1st ultrasound in 2nd trimester.
Patient Data
4 chamber view video
Normal atrioventricular concordance and cardiac axis. Physiological vieussens valve with physiological right to left atrial shunt.
Pericardial effusion, cardiomegaly, dilated right atrium due to tricuspid insufficiency (see pulsed Doppler waveform), and last but not least, critically low cardiac function: no systolic thickening of myocardium during systole, in both ventricles, except the base of right ventricle. Ejection volume seems obviously low. Hyperechoic myocardium.
Amniotic membrane is thin, and almost stuck to the skin of twin A: Twin A shows an oligohydramnios, while conversely twin B features polyhydramnios.
In twin A, neither heart nor orbits and face are identifiable, there is an omphalocele and an hydrocephaly.
Case Discussion
This case emphasizes US findings in high-output fetal cardiac failure at a late stage.
In this case, twin B's fetal cardiac output failure is due to a vascular steal syndrome from his acardiac, malformed, monochorial twin (the equivalent of a high flow tumor).
Other causes of fetal cardiac failure include complex cardiac malformations, anemia (from Rhesus alloimmunisation, or from fetal infections), vascular steal syndrome from arterioveinous malformations (for example Galen vein malformation) or from hypervascular fetal tumors, and other syndromic conditions.
Acardiac twin is one of the 3 classic complications of a monochorionic diamniotic pregnancy, with Twin-to-twin transfusion syndrome (TTTS) and Twin-Anemia-Polycythemia Syndrome (TAPS). Physiopathology of these complications involve arterio-arterial placental anastomosis (TTTS and acardiac twin) or arterio-veinous placental anastomosis (TAPS).
Watchful follow up of monochorial diamniotic pregnancies is useful to plan in utero treatment before fetal demise.
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