Case report

A 34-year-old woman (G1P0) with non-contributive history was sent to our facility at 19 weeks + 1 day of her monochorionic, diamniotic twin pregnancy. Our examination revealed twin-to-twin transfusion syndrome (TTTS) of the fetuses with following findings:

Twin A (XY, donor):

• severe oligohydramnios "stuck twin"
• bladder non-visualized
• EFW 209 g ± 31 g

Twin B (XY, recipient):

• polyhydramnios (DVP 85 mm)
• overfilled bladder
• tricuspid regurgitation
• EFW 273 g ± 40 g

Image 01: Scheme showing relations of the placenta, insertions of the umbilical cords to the placenta, and position of the fetuses — donor ("stuck twin") and recipient with polyhydramnios during our examination at 19 weeks and 1 day of pregnancy.

The findings were consistent with TTTS stage II (Quintero), or TTTS IIIa (Cincinnati staging system). 

The patient was sent to a specialized fetal medicine center in Prague, Czech Republic, and successful fetoscopic laser photocoagulation of placental anastomoses was done at 19 weeks + 6 days of pregnancy.

19 days after fetoscopic laser photocoagulation following findings were found in fetus A (former donor):

Image 02, video 01: The image and the video show color Doppler four-chamber view of the of the donor fetal heart after laser treatment of the TTTS. Severe tricuspid regurgitation and cardiomegaly can be seen.

Image 03 and 04: The images show color Doppler sagittal view of the donor fetal heart after laser treatment of the TTTS. Aortic and ductal arches with reversed flow within the ductus arteriosus and pulmonary artery can be seen. 

Ao - aorta (aortic arch); PA - pulmonary artery; DA - ductus arteriosus.

Image 05 and 06: The images show color Doppler sagittal view of the donor fetal heart after laser treatment of the TTTS. Reversed blood jet from the pulmonary to the right ventricle can be seen.

PA - pulmonary artery; RV - right ventricle.

Image 07 and video 08: The image and the video show color Doppler transverse scan of the donor fetal heart after laser treatment of the TTTS. The level of the three-vessel view of the heart can be seen. Reversed blood within the pulmonary artery and reversed jet from the pulmonary to the right ventricle can be seen.

RV - right ventricle; PA - pulmonary artery; Ao - aorta; SVC - superior vena cava.

Video 03 and image 09: The video and image represent FetalHQ speckle tracking analysis (special software available in GE Voluson machines) of the donor fetal heart after laser treatment of the TTTS - cardiomegaly, ventricular dilatation, impaired contractility and fractional shortening predominantly affecting the right ventricle can be seen.

The above mentioned findings are consistent with so called Intracardiac Twin Circular Shunt, which is a form of severe right outflow tract obstruction described in literature [Pruetz et al, 1].

Twin Circular Intracardiac Shunt = shunt in which blood originating in one cardiac chamber is shunted through the heart to return to the original chamber without ever crossing a capillary bed.

Criteria for the twin circular intracardiac shunt are:

- right ventricular dysfunction
- tricuspid pulmonary regurgitation
- flow reversal in the ductus arteriosus
- pulmonary regurgitation

Images 10 and 11: The images showing cardiac drawings explaining the principle of intracardiac twin circular shunt - antegrade flow across the tricuspid valve is diminished and the blood from the right ventricle (RV) returns back to the right atrium (RA) due to tricuspid regurgitation. This blood together with the blood entering the right atrium via inferior and superior vena cave is enters the left atrium (LA) via the foramen ovale and enters the aorta. Pulmonary artery (PA) is perfused retrogradely via ductus arteriosus (DA) and pulmonary regurgitation during diastole enables the blood in the pulmonary artrey to return back to the right ventricle. This way the circular shunt within the heart closes its vicious circle: RV - RA - foramen ovale - LA - LV - Ao - DA - PA - RV.

Cardiac anomalies, including right ventricular outflow tract obstruction (RVOTO) or twin circular intracardiac shunt typically affect recipient twin. Interestingly, in our case the donor was affected.

Laser intervention at an early stage of TTTS associated with a significant reduction in the incidence of RVOTO. A prediction model for the risk of RVOTO at birth in TTTS recipients was constructed - abnormal flow in the DV, pericardial effusion and early gestational age at onset of TTTS are predictors of RVOTO in TTTS recipients (Eschbach SJ et al., 2017), [2].

RVOTO can develop after laser treatment or even in the neonatal period and in all Quintero stages (Eschbach SJ et al., 2018), [3].

Donor twin is rarely affected by the RVOTO and the pathomechanism of this phenomenon in donor twin is still not fully clarified.

References

1. Pruetz JD, Votava-Smith JK, Chmait HR, Korst LM, Llanes A, Chmait RH. Recipient Twin Circular Shunt Physiology Before Fetal Laser Surgery: Survival and Risks for Postnatal Right Ventricular Outflow Tract Obstruction. J Ultrasound Med. 2017 Aug;36(8):1595-1605. doi: 10.7863/ultra.16.08038. Epub 2017 Apr 3. PubMed PMID: 28370096

2. Eschbach SJ, Boons LSTM, Van Zwet E, Middeldorp JM, Klumper FJCM, Lopriore E, Teunissen AKK, Rijlaarsdam ME, Oepkes D, Ten Harkel ADJ, Haak MC. Right ventricular outflow tract obstruction in complicated monochorionic twin pregnancy. Ultrasound Obstet Gynecol. 2017 Jun;49(6):737-743. doi: 10.1002/uog.16008. Epub 2017 May 2. PubMed PMID: 27363529.

3. Eschbach SJ, Ten Harkel ADJ, Middeldorp JM, Klumper FJCM, Oepkes D, Lopriore E, Haak MC. Acquired right ventricular outflow tract obstruction in twin-to-twin transfusion syndrome; a prospective longitudinal study. Prenat Diagn. 2018 Dec;38(13):1013-1019. doi: 10.1002/pd.5378. Epub 2018 Nov 28. PubMed PMID: 30365169.