title: Noninvasive assessment of vascular function and hydraulic power and efficiency in pediatric Fontan patients.
abstract: BACKGROUND
  Invasive studies have shown that children with Fontan palliation have abnormal arterial stiffness, impedance, and hydraulic power and efficiency. The aim of this study was to assess these indexes noninvasively in a cohort of children with Fontan circulation using Doppler echocardiography and compare their results with those of healthy peers.
  
  
  METHODS
  This was a case-control study of 22 Fontan patients and 31 healthy control children. Using standard two-dimensional, M-mode, and Doppler echocardiographic imaging and carotid artery applanation tonometry, aortic flows, dimensions, and pulse-wave velocity were measured, and vascular impedance and arterial stiffness were calculated. Hydraulic power and efficiency were calculated from standard fluid dynamics formulae.
  
  
  RESULTS
  The median age was similar between groups. Stroke volume index (39 vs 39 mL/min/m(2)) and cardiac index (2.6 vs 2.5 L/min/m(2)) were similar. Aortic cross-sectional area (3.3 vs 2.8 cm(2)), peak aortic flow (302 vs 261 cm(3)/sec), and myocardial performance index (0.47 vs 0.25) were higher and ejection fraction (50% vs 66%) was lower in Fontan patients. Input impedance (61 vs 83 dyne · sec/cm(5)/m(2)) was lower in Fontan patients. Pulse-wave velocity (488 vs 364 cm/sec), elastic pressure-strain modulus (305 vs 263 torr), and stiffness index (4.15 vs 3.04) were higher in Fontan patients. Total arterial compliance (1.29 vs 1.32 mL/torr/m(2)) and mean power (606 vs 527 mW/m(2)) were similar and total hydraulic power (716 vs 627 mW/m(2)) was higher in Fontan patients. Efficiency and the power cost per unit of forward flow were similar.
  
  
  CONCLUSIONS
  Despite stiffer aortas, Fontan patients generate more hydraulic power associated with decreased ventricular function to achieve a similar hydraulic efficiency. In Fontan patients, therapy that is given to improve ventricular function may need to target vascular stiffness as well. This technique may be used to monitor the efficacy of therapeutic interventions.
authors.affiliation: Children's Heart Centre, British Columbia Children's Hospital, and the Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Kimberley A
authors.initials: KA
authors.lastname: Myers
authors.affiliation: Children's Heart Centre, British Columbia Children's Hospital, and the Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Mande T
authors.initials: MT
authors.lastname: Leung
authors.affiliation: Children's Heart Centre, British Columbia Children's Hospital, and the Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Terri Potts
authors.affiliation: Children's Heart Centre, British Columbia Children's Hospital, and the Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: James E
authors.initials: JE
authors.lastname: Potts
authors.affiliation: Children's Heart Centre, British Columbia Children's Hospital, and the Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address: gsandor@cw.bc.ca.
authors.forename: George G S
authors.initials: GGS
authors.lastname: Sandor
mesh_terms: D000293:Adolescent; D001011:Aorta / Q000502:physiology*; D002339:Carotid Arteries / Q000503:physiopathology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D015150:Echocardiography, Doppler; D005260:Female; D018729:Fontan Procedure; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008365:Manometry; D011446:Prospective Studies; D012039:Regional Blood Flow; D059289:Vascular Stiffness / Q000502:physiology*; D016276:Ventricular Function
keywords: ACE; Angiotensin-converting enzyme; CI; Cardiac index; Characteristic impedance; Elastic pressure-strain modulus; Ep; Fontan procedure; Fourier-derived characteristic impedance; Fourier-derived input impedance; Hydraulic efficiency; Hydraulic power; Hydraulic power and efficiency; Input impedance; MPI; Mean power; Myocardial performance index; PWV; Power cost per unit of forward flow; Pulse-wave velocity; TAC; Total arterial compliance; Total power; Vascular impedance; W; W(m); W(m)/W(t); W(t); W(t)/CI; Zc; ZcF; Zi; ZiF