Case of TTTS hypovolemia 

January 2024

By Pasinee Kanaprach (Fellow in Neonatal Hemodynamics - McGill University) under supervision of Gabriel Altit. 

January 16, 2024.


We here present a case where a TnECHO evaluation played a pivotal role in guiding interventions for a monochorionic diamniotic (MDCA) twin, born at 26+1 weeks, diagnosed with twin-to-twin transfusion syndrome (TTTS). At 25+6 weeks, prenatal assessments unveiled stage 3 of the syndrome, polyhydramnios, and absent end-diastolic flow in the umbilical venous circulation in the recipient twin. The donor twin presented with oligohydramnios, an absent bladder, and a 5.9% weight discordance.


The babies were born by an urgent Caesarean section, prompted by preterm labor and pain. At birth, this newborn had Apgar scores of 2, 2, and 4, with an initial lactate of 18 mmol/L. This newborn was the recipient twin. The baby required surfactant administration for respiratory distress syndrome, followed by continued conventional ventilation. Oliguria/anuria appeared within the first 24 hours, and despite stable vital signs, hypotension progressively developed at 48 hours of life, leading to interventions by the clinical team of introduction of Dopamine and hydrocortisone.


A TnECHO was requested by the clinical team and revealed an underfilled volume status with right ventricular hypertrophy, adequate systolic function under inotropic support, physiologic tricuspid regurgitation, and a small, non-hemodynamically significant patent ductus arteriosus that was left to right throughout the cardiac cycle. Judicious administration of isotonic fluid and discontinuation of dopamine and hydrocortisone at the 9-hour mark led to a noticeable improvement in urine output (2-3 mL/kg/hour) and complete resolution of the hypotension events. Serum creatinine levels, assessed on day of life 2 at 80, peaked at 110 on day of life 4 before showing a descending trend. In contrast, the donor twin remained stable without inotropic support but exhibited an elevated creatinine level of 116 umol/L on the second day of life, with low-normal urine output gradually improving.


TTTS, involving inter-twin transfusion within the shared placenta of monochorionic twins, affects 10-15% of MCDA twins, causing circulatory imbalances and hypovolemia in the donor and hypervolemia in the recipient fetus. Untreated TTTS poses a substantial risk of perinatal mortality and long-term adverse effects on cardiovascular and neurological systems. The recipient experiences hypervolemia, releasing natriuretic peptides (ANP, BNP), leading to increased glomerular filtration rate, heightened urine output, and polyhydramnios. Donor-to-recipient transfer of Endothelin-1 and discordant renin angiotensin aldosterone (RAA) system activation contributes to the renal and cardiovascular changes. These biomarkers are transferred from one twin to the other, creating paradoxical effects. Reduced blood flow in the donor alters arterial structure, inducing vascular stiffness and long-term hypertension in both twins. The Myocardial Performance Index (MPI) consistently shows elevated values in recipients across TTTS stages. Donor hypovolemia also impacts renal function. Fetoscopic Laser Vascular ablation in advanced stages disrupts the pathophysiology, improving cardiovascular function post-treatment. Understanding the TTTS-related cardiovascular changes is crucial for managing TTTS safely in the postnatal life. Key insights involve understanding TTTS pathogenesis and recognizing multisystem manifestations. In this case, TnEcho proved to be an efficacious evaluation that allowed for guided intervention grounded in physiology, avoiding unnecessary procedures and potential side effects.



Echocardiography findings

Small patent ductus arteriosus that is left to right throughout the cardiac cycle, indicating that the PA pressures is lower than the systemic pressures.

Restrictive shunt (left to right) with peak gradient in systole of 9 mmHg (indicating that the pressure is about 9 mmHg below the systolic systemic pressure. 

Parasternal short axis sweep indicating RV hypertrophy. There is already suspcion of underfilling of the ventricles with kissing walls of the left and right ventricles as we sweep towards the apex.

Parasternal short axis outlining filling of the RV by colour through the tricuspid valve.

Apical 4 chamber view by B-Mode outlining the underfilling of both ventricles (kissing walls). The RV seems hypertrophied (although underfilled).

Acceleration by colour intra-cavitary of the RV despite Nyquist at 108 cm/s.

Filling of outflow tract of the LV is observed by colour. Intracavitary acceleration of the LV with Nyquist at 108 cm/s (velocity filter).

Filling is observed through the mitral valve in the Apical 4 chamber view. The walls are approximating to each other during systole, suspecting underfilling. 

Apical 4 chamber view

Apical 2 chamber view outlining the kissing ventricular walls, leading to a strong suspicion of a need for fluid repletion. 

Low VTI in the descending abdominal aorta, outlining a decrease in LV output filling the descending aorta in systole with a sharp upstroke. This is suspicious for a low volume status.

Low VTI in the LVOT, outlining a decrease in LV output filling the descending aorta in systole with a sharp upstroke. This is suspicious for a low volume status.

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