Twin Twin Transfusion Syndrome

The receiver often has congestive heart failure. The donor often has hypertrophic heart failure. For the recipient, there is increased preload (volume) with an absolute increase in circulating volume compared to that of the donor, with significantly higher cardiac output. The recipient is also subjected to an increased afterload in the form of increased resistance. The renin-angiotensin system (RAS) is ‘downregulated’ in the recipient's kidneys, but work has shown that the levels are as high as in the donor; it is assumed that this is mainly due to transfer from the donor. All these factors explain the development of significant myocardial ventricular hypertrophy, out of proportion to simple volume overload. A consequence of this progressive cardiomyopathy is an increase in overall heart size, a reduction in myocardial compliance, atrioventricular valvar regurgitation, and abnormal venous Dopplers. RVOT anomalies in the recipient may be in the form of valvar dysplasia, stenosis, regurgitation, or functional atresia; early involvement of the RVOT may be demonstrated by observing that the pulmonary valve annulus is equal in size to or smaller than that of the aortic valve, and this can progress to produce significant valvar pathology. It is not clear whether RVOT anomalies mirror the severity of the TTTS process, or whether the anomalies are simply due to altered hemodynamics or are a consequence of the vasoactive mediators. The prevalence of RVOT anomalies varies in different series but may be seen in some form in up to 20% of MC/DA twins, but only in recipient twins; between 9 and 12.5% had persistent anomalies requiring postnatal treatment, in spite of otherwise successful treatment for the TTTS.

Reference for Data and Figure: Manning N, Archer N. Cardiac Manifestations of Twin-to-Twin Transfusion Syndrome. Twin Res Hum Genet. 2016 Jun;19(3):246-54. doi: 10.1017/thg.2016.20. Epub 2016 Apr 18. PMID: 27087122.

TTTS - Hemodynamic evaluation and management by Dr. Anie Lapointe


Presentation by Dr Ida Whiteman and Mrs Kristina Huber in the context of Neonatal Cardiology Rounds on TTTS on March 13, 2024

TTTS Final.pdf

Case of Pulmonary Stenosis in the recipient twin 

Parasternal long axis B-Mode. There is a sweep anteriorly. One may appreciate the RV hypertrophy with the significant narrowing of the RVOT and underlying pulmonary stenosis (with small pulmonary valvular annulus)

PLAX with acceleration of flow in at the pulmonary valve (aliasing seen at a velocity filter/Nyquiest of -1.14 m/s)

PDA is seen left to right, potentially contributing to pulmonary blood flow. 

PDA measured at 2.2 mm in 2D.

Modified view where one may appreciate that the pulmonary valve is doming and that its opening is narrowed - outlining some 2D evidence of underlying pulmonary stenosis.

Turbulence of flow / alliasing in the RVOT by colour. 

2D view clip and 2D still frame with measurement of the pulmonary valvular annulus. 

Parasternal short axis with colour and B-mode. The colour showcases aliasing from the turbulence of flow created by the pulmonary stenosis. One may also appreciate some of the PDA flow feeding into the branche pulmonary arteries. 

Apical view sweep from posterior to anterior where we can appreciate the RVOT and pulmonary valve. The Pulmonary valve annulus is measured at 0.31 cm.

Colour flow through the RVOT into the branch pulmonary arteries.

Gradient obtained from the Parasternal Long axis view outlining a RV-MPA gradient of 128 mmHg (stenosis of the pulmonary valve). There is a dagger-shaped high-velocity Doppler spectra outlining there is a dynamic component to the obstruction.

Subcostal view with CW-Doppler in the RVOT with a gradient of 133.7 mmHg RV to PA, outlining significant pulmonary stenosis. 

Subcostal view with 2D sweep and colour (outlining an inter-atrial shunt that is bidirectional, but significantly right to left due to increase RV end-diastolic pressure).

Case of significant hypertrophy in the context of a recipient twin

Intra-cavitary acceleration from the hypertrophy of the LV.

Systolic anterior motion of the mitral valve on M-Mode secondary to the hypertrophic state.

Intra-cavitary gradient detected by CW Doppler

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