title: Twin-reversed arterial perfusion sequence associated with decreased fetal cerebral vascular impedance.
abstract: OBJECTIVE
  Twin-reversed arterial perfusion (TRAP) sequence affects 1% of monochorionic twin pregnancies and is caused by abnormal vascular connections between a pump twin and an acardiac mass. The effects of abnormal vascular connections on cerebral vasculature in the pump twin are unknown. We hypothesize that abnormal cerebral vascular impedance, as assessed by the pulsatility index (PI), is present in pump twins and that fetal intervention alters cerebral impedance.
  
  
  METHODS
  Fetal echocardiograms performed between 2010 and 2013 in pregnancies diagnosed with TRAP (n = 19), recorded at presentation, and uncomplicated monochorionic twin pregnancies (controls, n = 18; 36 fetuses) were analyzed. In all subjects, the middle cerebral artery (MCA)-PI, combined cardiac output (CCO) and cardiothoracic ratio were calculated, and the values for cases and controls were compared.
  
  
  RESULTS
  The mean gestational age at the time of echocardiography was 20 weeks in both groups. MCA-PI was lower in TRAP cases than in controls (1.55 (95% CI, 1.47-1.64) vs 1.74 (95% CI, 1.65-1.82), respectively; P = 0.004). CCO in TRAP cases was mildly elevated for gestational age (199.7 (95% CI, 138.4-261.1) mL/min) compared with that of controls (131.4 (95% CI, 102.2-160.7) mL/min). In six TRAP cases with a second echocardiogram available, the mean MCA-PI increased after intervention, from 1.5 (95% CI, 1.3-1.7) to 1.8 (95% CI, 1.4-2.2).
  
  
  CONCLUSIONS
  TRAP pump twins have lower cerebral vascular impedance than do controls, suggestive of a brain-sparing effect. MCA-PI appeared to increase in a small group of pump twins after intervention. These findings suggest a fetal cerebral autoregulatory response to a high cardiac output state that begins to change after fetal intervention. The long-term implications for neurodevelopmental outcome warrant further study.
authors.affiliation: Division of Cardiology, Department of Pediatrics, University of California San Francisco Benioff Children's Hospital, San Francisco, CA, USA; The Fetal Treatment Center, University of California San Francisco Benioff Children's Hospital, San Francisco, CA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Peyvandi
authors.forename: V A
authors.initials: VA
authors.lastname: Feldstein
authors.forename: S
authors.initials: S
authors.lastname: Hirose
authors.forename: L
authors.initials: L
authors.lastname: Rand
authors.forename: M M
authors.initials: MM
authors.lastname: Brook
authors.forename: A J
authors.initials: AJ
authors.lastname: Moon-Grady
mesh_terms: D004452:Echocardiography; D005260:Female; D005330:Fetofetal Transfusion / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005333:Fetus / Q000002:abnormalities / Q000098:blood supply*; D006801:Humans; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging*; D065886:Neurodevelopmental Disorders / Q000000981:diagnostic imaging / Q000503:physiopathology; D010920:Placenta / Q000098:blood supply / Q000000981:diagnostic imaging; D011247:Pregnancy; D059285:Pregnancy, Twin; D011673:Pulsatile Flow / Q000502:physiology; D061208:Pulsed Radiofrequency Treatment / Q000379:methods; D015996:Survival Rate; D014427:Twins; D016216:Ultrasonography, Prenatal
keywords: TRAP; cerebral vascular impedance; fetal cardiology; neurodevelopment