Hypothesis acardiac twin pregnancies: Pathophysiology‐based hypotheses suggest risk prediction by pump/acardiac umbilical venous diameter ratios

Abstract

Our data provide first evidence that UVD-ratios allow risk prediction of pump twins. More early uncomplicated and late complicated cases are needed, for example, in a prospective trial, before the separation between uncomplicated and complicated cohorts is accurate enough to support a well-founded decision on (early) intervention.

Acardiac twin pregnancies part IV: Acardiac onset from unequal embryonic splitting simulated by a fetoplacental resistance model

“…Without intrauterine intervention, the mortality rate of pump twins is approximately 50% (Moore et al, ; Healy, ). An accepted method for risk prediction of pump twins is currently lacking; however, we recently proposed a simple pathophysiology‐based clinical approach based on measurement of pump/acardiac umbilical venous diameter (UVD) ratios because they represent the fraction of the pump twin's excess cardiac output that it needs for perfusion of the acardiac body (van Gemert et al, ). The acardiac umbilical artery and aorta are perfused in a reversed direction, so acardiac twin pregnancies are often named the twin reversed‐arterial perfusion sequence (Van Allen et al, ).…”

“…We implemented all these hypotheses in a linear resistance model of the fetoplacental circulation of two monochorionic twins of unequal driving pressure gradients connected by AA and VV anastomoses. We calculated the umbilical blood flows and derived from these the umbilical venous diameter ratios, as used in previous work (van Gemert et al, , ). We compared the model predictions with 18 of the 21 clinical cases we found of “pseudo‐acardiac” (twin fetus with beating heart but otherwise with clear signs of an acardiac) twinning (three of these 21, one by Fouron et al, ; and two by Shih et al, ; included insufficient information for comparison with our model), all with a beating heart and yet the typical signs of an acardiac twin, that is, retrograde umbilical flow, hypoxemia and malformations (Brand and Krol, ; two cases by Ko et al, ; Pavlova et al, ; Alves et al, ; six cases by Brassard et al, ; Bonilla‐Musoles et al, ; Driggers et al, ; two cases by Meyberg and Groß, ; Mivelaz et al, ; and two available cases from our group in Houston), and also with three available early cases of “normal” acardiac twin pregnancies.…”

Twin Reversed Arterial Perfusion Sequence: Assessing the Role of the Correct Imaging Modality in a Rare Clinical Entity

“…Cases with lower UVD ratios may be more likely to require earlier intervention than otherwise [8]. This can be achieved by in-utero techniques where treatment revolves around the ultrasound-guided or surgical destruction of the inter-twin anastomosis and includes [9-10]:…”

Acardiac twin pregnancies part II: Fetal risk of chorangioma and sacrococcygeal teratoma predicted by pump/acardiac umbilical vein diameters

“…Figure A shows the 27 pump/acardiac UVD ratios and the separation line (equation defined in caption) which was chosen to connect the UVD ratios of two cases with complications, at 16 and 35 weeks. This separation line has, however, no false positives or false negatives, and the data of the two cohorts have noncrossing linear trend lines (van Gemert et al, ).…”

“… (A) Data from Figure 4 of van Gemert et al (). The separation line between pump twins with and without complications was constructed by arbitrarily connecting two complicated cases at 16 and 35 weeks (UVD ratios of 2.27 and 1.17), and is given by , in weeks.…”