title: Understanding the Aortic Isthmus Doppler Profile and Its Changes with Gestational Age Using a Lumped Model of the Fetal Circulation.
abstract: OBJECTIVE
  The aortic isthmus (AoI) blood flow has a characteristic shape with a small end-systolic notch observed during the third trimester of pregnancy. However, what causes the appearance of this notch is not fully understood. We used a lumped model of the fetal circulation to study the possible factors causing the end-systolic notch and the changes of AoI flow through gestation.
  
  
  METHODS
  A validation of the model was performed by fitting patient-specific data from two normal fetuses. Then, different parametric analyses were performed to evaluate the major determinants of the appearance of the end-systolic notch. The changes in the AoI flow profile through gestation were assessed.
  
  
  RESULTS
  Our model allows to simulate the AoI waveform. The delay in the onset of ejection together with the longer ejection duration of the right ventricle are the most relevant factors in the origin of the notch. It appears around 25 weeks of gestation and becomes more pronounced with advancing gestation.
  
  
  CONCLUSIONS
  We demonstrated that the end-systolic notch on the AoI flow occurs mainly as a result of a delayed and longer ejection of the right ventricle. Our findings improve the understanding of hemodynamic changes in the fetal circulation and the interpretation of clinical imaging.
authors.affiliation: Fetal i+D Fetal Medicine Research Center, BCNatal - Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Deu), IDIBAPS, University of Barcelona, Barcelona, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Garcia-Canadilla
authors.forename: Fatima
authors.initials: F
authors.lastname: Crispi
authors.forename: Monica
authors.initials: M
authors.lastname: Cruz-Lemini
authors.forename: Brenda
authors.initials: B
authors.lastname: Valenzuela-Alcaraz
authors.forename: Paula A
authors.initials: PA
authors.lastname: Rudenick
authors.forename: Eduard
authors.initials: E
authors.lastname: Gratacos
authors.forename: Bart H
authors.initials: BH
authors.lastname: Bijnens
mesh_terms: D001013:Aorta, Thoracic / Q000000981:diagnostic imaging* / Q000196:embryology / Q000502:physiology; D003198:Computer Simulation; D005260:Female; D047109:Fetal Development; D005318:Fetal Heart / Q000000981:diagnostic imaging* / Q000502:physiology; D005333:Fetus / Q000000981:diagnostic imaging* / Q000502:physiology; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D012039:Regional Blood Flow; D012044:Regression Analysis; D016216:Ultrasonography, Prenatal