title: Pressure-volume loop-derived cardiac indices during dobutamine stress: a step towards understanding limitations in cardiac output in children with hypoplastic left heart syndrome.
abstract: BACKGROUND
  Children with a single systemic right ventricle, such as in hypoplastic left heart syndrome (HLHS), frequently experience reduced exercise capacity. Elucidating the causes could help with optimising treatment strategies.
  
  
  METHODS
  Prospective data from 10 consecutive symptomatic patients with HLHS undergoing clinical cardiac magnetic resonance with catheterisation (XMR) were analysed. Mean age 8.6years (range 3.5-11.6years), mean time since Fontan completion 5.5years. MR-compatible catheters were placed in the systemic right ventricle and branch pulmonary arteries to record pressures at rest, with dobutamine infusion at 10mcg/kg/min and at 20mcg/kg/min. Cine short-axis stacks of the ventricle were performed at each condition and used to construct pressure-volume loops.
  
  
  RESULTS
  Compared to rest, cardiac index increased with low-dose dobutamine (p<0.01) with no further rise at peak stress despite a further, albeit, blunted rise in heart rate (p=0.002). A fall in stroke volume occurred (p=0.014) despite good contractility (74% increase, p=0.045) and a well-coupled ventriculo-arterial ratio. End-diastolic pressure and early active relaxation, markers of diastolic function, were normal at rest. However, preload fell at peak stress (p<0.008) while pulmonary vascular resistance (PVR) was low throughout. This group of HLHS patients demonstrated a fall in SV at peak stress, coinciding with a fall in preload.
  
  
  CONCLUSIONS
  Markers of systolic and diastolic function remained normal. Failure to adequately fill the ventricle implies a ceiling of maximal flow through the Fontan circuit despite low PVR.
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom.
authors.forename: James
authors.initials: J
authors.lastname: Wong
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom.
authors.forename: Kuberan
authors.initials: K
authors.lastname: Pushparajah
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom.
authors.forename: Adelaide
authors.initials: A
authors.lastname: de Vecchi
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom.
authors.forename: Bram
authors.initials: B
authors.lastname: Ruijsink
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom.
authors.forename: Gerald F
authors.initials: GF
authors.lastname: Greil
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom.
authors.forename: Tarique
authors.initials: T
authors.lastname: Hussain
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom. Electronic address: reza.razavi@kcl.ac.uk.
authors.forename: Reza
authors.initials: R
authors.lastname: Razavi
mesh_terms: D001794:Blood Pressure / Q000502:physiology; D006328:Cardiac Catheterization; D002302:Cardiac Output / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D004280:Dobutamine; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D018636:Hypoplastic Left Heart Syndrome / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D014655:Vascular Resistance / Q000502:physiology
chemical_list: D004280:Dobutamine
keywords: Catheterisation; Congenital heart disease; Fontan procedure; Hypoplastic left heart syndrome; Magnetic resonance imaging