Q. How do the fetal echo and Doppler findings in a recipient twin compare and contrast to other volume overloads?  E.g. absent ductus venosus, etc.  Vasoactive compounds may differ since there is no donor twin to generate them–?

Great question-we asked that same question years ago as TTTS recipient often have hypertrophied ventricles with very high pressures and not always a dilated heart until there was more severe systolic dysfunction-We showed they have end diastolic diameters comparable to that of hypertrophic cardiomyopathies and did not look like babies with classic volume load (Fontes-Pedra Circ 2002) -Some have called this a “hypertensive cardiomyopathy”

Inflow duration is shortened and MPI and IVRT are lengthened in TTTS but not other volume overloads until late.  DV is more likely to be abnormal in TTTS even in the absence of hydrops.  Cardiac enlargement with hypertrophy in TTTS recip, different from cardiac chamber dilation with mild compensatory hypertrophy in high output.  Essentially they look totally different!

Q.Is any change of MCA Doppler for TTTS ?

Not related with TTTS, but instead related with TAPS. I sometimes refer to this as the “little sister” of TTTS.

Agree, MCA Dopplers should be concordant and normal even in TTTS.  If PSV is discordant, that’s TAPS.  TTTS and TAPS can co-exist though so we check MCA Doppler in all MC twins at every exam

There was a recent publication that suggested about 15% of TTTS cases did in fact have discordant PSV-MCA Dopplers suggestive of coexisting TAPS.

Q.Would a cerclage be placed before laser surgery

In our center and others, short cervix may be a contra-indication to laser given the very high risk of preterm delivery.  Always a discussion.  For normal cervix I’m not aware of prophylactic cerclage— there is a discussion about pessary better answered by MFM

Most fetal centers use a 2 cm threshold length for fetoscopic laser.  At our institution, we use 1.5 cm but we do place a cerclage at the time of the procedure.  We have tended to do this at the end of the case after the laser and amnioreduction which often results in a longer cervical length to work with . . .

Q. Diatolic dysfunction, with hypetrophy and low compliance, versus “pure” volume load in the setting of TTTS recipient, basically.

exactly

Q. Does site of cord insertion increase risk of adverse outcome, twin-to-twin transfusion syndrome?

The location of the cord insertions is very important to know. Here at our center, we will not offer laser surgery if the donor and recipient cord insertions are 2 centimeters apart or less. Even yet, up to 4 centimeters apart will be reason to cause us concern.

In our experience, close proximity of the PCIs can make complete dichorionization of the single placenta technically difficult – and therefore can lead to less favorable outcomes.

Q. How to detect TRAP in twin pregnancy and intervention?

Early discordant growth with recognition that smaller twin lacks a normal heart but continues to “grow”. To confirm, can look at Doppler in cord vessels and will be able to detect retrograde flow from pump to acardiac twin.

Q. Fetal therapy for heart block, is it only for twins or can it be treated with same medication for singleton?

Absolutely can treat singleton, yes

Q. CNS immaturity depends significantly on the type of CHD, correct?  A large factor with HLHS, for example, less with other lesions that have normal aortic flows.  (Good role for the hybrid procedure post-natally to postpone a bypass run…)

Yes, some studies suggest this immaturity is more significant with systemic outflow obstruction, but not consistently. You are right, that when those children have to be delivered early, they may be a better candidate for hybrid palliation to avoid early bypass

Q. Why do some newborns following treatment of TTTS appear to be doing well in utero and are both relatively normal at birth yet obviously are born with anemia and polycythemia?

Live answered

Q. When would you do TEIs with mono/di twins? Would it would routinely thoroughout the entire course of the pregnancy or only after other signs of TTTS/ abnormal Dopplers?

I think most of us would only do MPI if there is poly/oli

Q. Great talks! Curious to here what the panel thinks about the benefits of cardiac upstaging and/or if they just treat Stage 1 and above with SFLP?

Live answered

Q. Is there a significantly higher risk for perinatal brain injury in TTTS than other fetal diagnosed CHD?

I am not sure that I have seen these groups compared. My impression is that TTTS has greater risk in the perinatal time, while CHD risk is more subtle and throughout fetal life and childhood.

Q. Is the fetal cardiac output calculation used to evaluate TRAP in your institutions?

Yes, routinely.  See Byrne et al: https://pubmed.ncbi.nlm.nih.gov/22086180/ [pubmed.ncbi.nlm.nih.gov]

Q. One more question for the panel, do you routinely pretreat patients with CCB prior to laser surgery to provide  some after-loading of the Donor twin due to the RAS derangements? Thank you all for your time and expertise

I don’t think anyone outside Denver and Cincinatti do this