title: Magnetic Resonance-Augmented Cardiopulmonary Exercise Testing: Comprehensively Assessing Exercise Intolerance in Children With Cardiovascular Disease.
abstract: BACKGROUND
  Conventional cardiopulmonary exercise testing can objectively measure exercise intolerance but cannot provide comprehensive evaluation of physiology. This requires additional assessment of cardiac output and arteriovenous oxygen content difference. We developed magnetic resonance (MR)-augmented cardiopulmonary exercise testing to achieve this goal and assessed children with right heart disease.
  
  
  RESULTS
  Healthy controls (n=10) and children with pulmonary arterial hypertension (PAH; n=10) and repaired tetralogy of Fallot (n=10) underwent MR-augmented cardiopulmonary exercise testing. All exercises were performed on an MR-compatible ergometer, and oxygen uptake was continuously acquired using a modified metabolic cart. Simultaneous cardiac output was measured using a real-time MR flow sequence and combined with oxygen uptake to calculate arteriovenous oxygen content difference. Peak oxygen uptake was significantly lower in the PAH group (12.6±1.31 mL/kg per minute; P=0.01) and trended toward lower in the tetralogy of Fallot group (13.5±1.29 mL/kg per minute; P=0.06) compared with controls (16.7±1.37 mL/kg per minute). Although tetralogy of Fallot patients had the largest increase in cardiac output, they had lower resting (3±1.2 L/min per m2) and peak (5.3±1.2 L/min per m2) values compared with controls (resting 4.3±1.2 L/min per m2and peak 6.6±1.2 L/min per m2) and PAH patients (resting 4.5±1.1 L/min per m2and peak 5.9±1.1 L/min per m2). Both the PAH and tetralogy of Fallot patients had blunted exercise-induced increases in arteriovenous oxygen content difference. However, only the PAH patients had significantly reduced peak values (6.9±1.3 mlO2/100 mL) compared with controls (8.4±1.4 mlO2/100 mL; P=0.005).
  
  
  CONCLUSIONS
  MR-augmented cardiopulmonary exercise testing is feasible in both healthy children and children with cardiac disease. Using this novel technique, we have demonstrated abnormal exercise patterns in oxygen uptake, cardiac output, and arteriovenous oxygen content difference.
authors.affiliation: From the Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, United Kingdom (N.J.B., E.O.A., G.T.K., M.H.C., J.A.S., V.M.); Great Ormond Street Hospital, London, United Kingdom (N.J.B., G.T.K., M.H.C., J.A.S., S.M., V.M.); and Bart's Heart Centre, London, United Kingdom (E.O.A., B.P.).
authors.forename: Nathaniel J
authors.initials: NJ
authors.lastname: Barber
authors.affiliation: From the Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, United Kingdom (N.J.B., E.O.A., G.T.K., M.H.C., J.A.S., V.M.); Great Ormond Street Hospital, London, United Kingdom (N.J.B., G.T.K., M.H.C., J.A.S., S.M., V.M.); and Bart's Heart Centre, London, United Kingdom (E.O.A., B.P.).
authors.forename: Emmanuel O
authors.initials: EO
authors.lastname: Ako
authors.affiliation: From the Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, United Kingdom (N.J.B., E.O.A., G.T.K., M.H.C., J.A.S., V.M.); Great Ormond Street Hospital, London, United Kingdom (N.J.B., G.T.K., M.H.C., J.A.S., S.M., V.M.); and Bart's Heart Centre, London, United Kingdom (E.O.A., B.P.).
authors.forename: Gregorz T
authors.initials: GT
authors.lastname: Kowalik
authors.affiliation: From the Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, United Kingdom (N.J.B., E.O.A., G.T.K., M.H.C., J.A.S., V.M.); Great Ormond Street Hospital, London, United Kingdom (N.J.B., G.T.K., M.H.C., J.A.S., S.M., V.M.); and Bart's Heart Centre, London, United Kingdom (E.O.A., B.P.).
authors.forename: Mun H
authors.initials: MH
authors.lastname: Cheang
authors.affiliation: From the Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, United Kingdom (N.J.B., E.O.A., G.T.K., M.H.C., J.A.S., V.M.); Great Ormond Street Hospital, London, United Kingdom (N.J.B., G.T.K., M.H.C., J.A.S., S.M., V.M.); and Bart's Heart Centre, London, United Kingdom (E.O.A., B.P.).
authors.forename: Bejal
authors.initials: B
authors.lastname: Pandya
authors.affiliation: From the Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, United Kingdom (N.J.B., E.O.A., G.T.K., M.H.C., J.A.S., V.M.); Great Ormond Street Hospital, London, United Kingdom (N.J.B., G.T.K., M.H.C., J.A.S., S.M., V.M.); and Bart's Heart Centre, London, United Kingdom (E.O.A., B.P.).
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Steeden
authors.affiliation: From the Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, United Kingdom (N.J.B., E.O.A., G.T.K., M.H.C., J.A.S., V.M.); Great Ormond Street Hospital, London, United Kingdom (N.J.B., G.T.K., M.H.C., J.A.S., S.M., V.M.); and Bart's Heart Centre, London, United Kingdom (E.O.A., B.P.).
authors.forename: Shahin
authors.initials: S
authors.lastname: Moledina
authors.affiliation: From the Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, United Kingdom (N.J.B., E.O.A., G.T.K., M.H.C., J.A.S., V.M.); Great Ormond Street Hospital, London, United Kingdom (N.J.B., G.T.K., M.H.C., J.A.S., S.M., V.M.); and Bart's Heart Centre, London, United Kingdom (E.O.A., B.P.). v.muthurangu@ucl.ac.uk.
authors.forename: Vivek
authors.initials: V
authors.lastname: Muthurangu
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002302:Cardiac Output; D006348:Cardiac Surgical Procedures / Q000009:adverse effects; D000072599:Cardiorespiratory Fitness; D016022:Case-Control Studies; D002648:Child; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance; D005240:Feasibility Studies; D005260:Female; D006304:Health Status; D006801:Humans; D006976:Hypertension, Pulmonary / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D015588:Observer Variation; D010101:Oxygen Consumption; D011237:Predictive Value of Tests; D011665:Pulmonary Valve Insufficiency / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D015203:Reproducibility of Results; D013318:Stroke Volume; D013771:Tetralogy of Fallot / Q000601:surgery*; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right
keywords: cardiovascular magnetic resonance imaging; exercise physiology; pediatric; pulmonary hypertension; tetralogy of Fallot