title: Haemodynamic resistance model of monochorionic twin pregnancies complicated by acardiac twinning.
abstract: An acardiac twin is a severely malformed monochorionic twin fetus that lacks most organs, particularly a heart. It grows during pregnancy, because it is perfused by its developmentally normal co-twin (called the pump twin) via a set of placental arterioarterial and venovenous anastomoses. The pump twin dies intrauterine or neonatally in about 50% of the cases due to congestive heart failure, polyhydramnios and prematurity. Because the pathophysiology of this pregnancy is currently incompletely understood, we modified our previous haemodynamic model of monochorionic twins connected by placental vascular anastomoses to include the analysis of acardiac twin pregnancies. We incorporated the fetoplacental circulation as a resistance circuit and used the fetal umbilical flow that perfuses the body to define fetal growth, rather than the placental flow as done previously. Using this modified model, we predicted that the pump twin has excess blood volume and increased mean arterial blood pressure compared to those in the acardiac twin. Placental perfusion of the acardiac twin is significantly reduced compared to normal, as a consequence of an increased venous pressure, possibly implying reduced acardiac placental growth. In conclusion, the haemodynamic analysis may contribute to an increased knowledge of the pathophysiologic consequences of an acardiac body mass for the pump twin.
authors.affiliation: Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Asli
authors.initials: A
authors.lastname: Umur
authors.forename: Martin J C
authors.initials: MJ
authors.lastname: van Gemert
authors.forename: Jeroen P H M
authors.initials: JP
authors.lastname: van den Wijngaard
authors.forename: Michael G
authors.initials: MG
authors.lastname: Ross
authors.forename: Peter G J
authors.initials: PG
authors.lastname: Nikkels
mesh_terms: D001703:Biophysics / Q000379:methods*; D018376:Cardiovascular Abnormalities / Q000473:pathology; D004200:Diseases in Twins; D005260:Female; D005313:Fetal Death; D005333:Fetus / Q000098:blood supply*; D005865:Gestational Age; D006330:Heart Defects, Congenital; D006439:Hemodynamics; D006801:Humans; D008953:Models, Anatomic; D008962:Models, Theoretical; D021041:Placental Circulation; D011247:Pregnancy; D013997:Time Factors; D014427:Twins; D014430:Twins, Monozygotic; D014652:Vascular Diseases