title: Non-invasive stroke volume measurement by cardiac magnetic resonance imaging and inert gas rebreathing in pulmonary hypertension.
abstract: OBJECTIVE
  Right ventricular function determines the prognosis of pulmonary hypertension (PAH). Measurement of stroke volume (SV) non-invasively could be a promising method to monitor disease progression. Cardiac magnetic resonance (CMR) imaging is recognized as an accurate and reproducible method to measure SV. Inert gas rebreathing (IGR) using acetylene is a validated but cumbersome method for pulmonary blood flow (PBF) measurement in PAH. A more convenient rebreathing technique using rapid photoacoustic analysis of nitrous oxide has been introduced and validated in left heart failure. We investigated the accuracy of CMR imaging and IGR using photoacoustic analysis to measure SV in patients under investigation for PAH.
  
  
  METHODS
  Thirty-three patients (16♀:17♂) with suspected PAH following echocardiography had SV measured by CMR imaging (using pulmonary arterial{CMR PA} and aortic {CMR Ao} flow methods) and IGR. The results were compared with our reference standard: thermodilution (TD) measured during right heart catheterization (RHC).
  
  
  RESULTS
  All methods showed similar correlation for SV. Bland-Altman analysis confirmed acceptable levels of agreement between the four techniques. TD versus CMR Ao flow had bias (limits of agreement) of -5.41 ml (-22.37 to 11.56 ml), TD versus CMR PA flow 0.12 ml (-20.13 to 20.37 ml) and TD versus IGR 6.25 ml (-16.01 to 28.51 ml).
  
  
  CONCLUSIONS
  Cardiac magnetic resonance imaging and IGR using photoacoustic analysis in patients with suspected PAH provided non-invasive measurements of SV that agreed closely with those obtained from TD measured during RHC.
authors.affiliation: Scottish Pulmonary Vascular Unit, Golden Jubilee National Hospital, Clydebank, West Dunbartonshire, Scotland, UK.
authors.forename: Lindsey E R
authors.initials: LE
authors.lastname: McLure
authors.forename: Aileen
authors.initials: A
authors.lastname: Brown
authors.forename: Waiting N
authors.initials: WN
authors.lastname: Lee
authors.forename: Alistair C
authors.initials: AC
authors.lastname: Church
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Peacock
authors.forename: Martin K
authors.initials: MK
authors.lastname: Johnson
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D001794:Blood Pressure; D001944:Breath Tests; D006328:Cardiac Catheterization; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012606:Scotland; D013318:Stroke Volume; D013815:Thermodilution; D016278:Ventricular Function, Right
chemical_list: D009609:Nitrous Oxide