title: Mechanisms of maintained exercise capacity in adults with repaired tetralogy of Fallot.
abstract: BACKGROUND
  The mechanisms whereby cardiac output is augmented with exercise in adult repaired tetralogy of Fallot (TOF) are poorly characterised.
  
  
  METHODS
  16 repaired TOF patients (25 ± 7 years of age) and 8 age and sex matched controls (25 ± 4 years of age) underwent cardiopulmonary exercise testing and then real-time cardiac MRI (1.5 T) at rest and whilst exercising within the scanner, aiming for 30% heart rate reserve (Level 1) and 60% heart rate reserve (Level 2), using a custom-built MRI compatible foot pedal device.
  
  
  RESULTS
  At rest, TOF patients had severely dilated RVs (indexed RV end-diastolic volume: 149 ± 37 mL/m(2)), moderate-severe PR (regurgitant fraction 35 ± 12%), normal RV fractional area change (FAC) (52 ± 7%) and very mildly impaired exercise capacity (83 ± 15% of predicted maximal work rate). Heart rate and RV FAC increased significantly in TOF patients (75 ± 10 vs 123 ± 17 beats per minute, p<0.001; 44 ± 7 vs 51 ± 10%, p=0.025), and similarly in control subjects (70 ± 11 vs 127 ± 12 beats per minute, p<0.001; 49 ± 7 vs 61 ± 9%, p=0.003), when rest was compared to Level 2. PR fraction decreased significantly but only modestly, from rest to Level 2 in TOF patients (37 ± 15 to 31 ± 15%, p=0.002). Pulmonary artery net forward flow was maintained and did not significantly increase from rest to Level 2 in TOF patients (70 ± 19 vs 69 ± 12 mL/beat, p=0.854) or controls (93 ± 9 vs 95 ± 21 mL/beat, p=0.648).
  
  
  CONCLUSIONS
  During exercise in repaired TOF subjects with dilated RV and free PR, increased total RV output per minute was facilitated by an increase in heart rate, an increase in RV FAC and a decrease in PR fraction.
authors.affiliation: The University of Sydney, Faculty of Medicine, Sydney, Australia; Royal Prince Alfred Hospital, Department of Cardiology, Sydney, Australia. Electronic address: shamus.omeagher@sswahs.nsw.gov.au.
authors.forename: Shamus
authors.initials: S
authors.lastname: O'Meagher
authors.affiliation: Royal Prince Alfred Hospital, Department of Respiratory and Sleep Medicine, Sydney, Australia. Electronic address: Phillip.munoz@sswahs.nsw.gov.au.
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Munoz
authors.affiliation: UCL Institute of Cardiovascular Science, Centre for Cardiovascular Imaging, London, United Kingdom; Cardiorespiratory Unit, Great Ormond Street Hospital for Children, London, United Kingdom. Electronic address: v.muthurangu@ucl.ac.uk.
authors.forename: Vivek
authors.initials: V
authors.lastname: Muthurangu
authors.affiliation: Royal Prince Alfred Hospital, Department of Cardiology, Sydney, Australia; Westmead Hospital, Department of Cardiology, Sydney, Australia. Electronic address: pjr5055@gmail.com.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Robinson
authors.affiliation: Specialist MRI, Sydney, Australia. Electronic address: nathan.malitz@smri.com.au.
authors.forename: Nathan
authors.initials: N
authors.lastname: Malitz
authors.affiliation: Royal Prince Alfred Hospital, Department of Cardiology, Sydney, Australia; Westmead Hospital, Department of Cardiology, Sydney, Australia. Electronic address: davidjtanous@gmail.com.
authors.forename: David J
authors.initials: DJ
authors.lastname: Tanous
authors.affiliation: The University of Sydney, Faculty of Medicine, Sydney, Australia; Royal Prince Alfred Hospital, Department of Cardiology, Sydney, Australia. Electronic address: david.celermajer@email.cs.nsw.gov.au.
authors.forename: David S
authors.initials: DS
authors.lastname: Celermajer
authors.affiliation: The University of Sydney, Faculty of Medicine, Sydney, Australia; Royal Prince Alfred Hospital, Department of Cardiology, Sydney, Australia. Electronic address: raj.puranik@cmrs.org.au.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Puranik
mesh_terms: D000328:Adult; D006348:Cardiac Surgical Procedures; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods; D008297:Male; D011446:Prospective Studies; D013318:Stroke Volume / Q000502:physiology*; D013771:Tetralogy of Fallot / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D016276:Ventricular Function / Q000502:physiology*
keywords: Adult congenital heart disease; Cardiac magnetic resonance imaging; Exercise; Left ventricular function; Right ventricular function; Tetralogy of Fallot