title: Assessment of left ventricular preload by cardiac magnetic resonance imaging predicts exercise capacity in adult operated tetralogy of Fallot: a retrospective study.
abstract: BACKGROUND
  The optimal timing of pulmonary homograft valve replacement (PVR) is uncertain. Cardiopulmonary exercise testing (CPET) and cardiac magnetic resonance (CMR) are often used to guide the clinical decision for PVR in operated tetralogy of Fallot (TOF) patients with significant pulmonary regurgitation (PR). We aim to study the relationship between exercise capacity and CMR in these patients.
  
  
  METHODS
  The study is a single-centre retrospective analysis of 36 operated TOF patients [median 21.4 (interquartile range 16.4, 26.4) years post-repair; 30 NYHA I, 6 NYHA II; median age 25.2 (interquartile range 19.5-31.7) years, 29 males] with significant PR on CMR who underwent CPET within 15 [median 2.0 (interquartile range 0.8-7.2)] months from CMR. CPET parameters were compared with 30 age- and sex-matched healthy controls [median age 27.8 (interquartile range 21.0-32.8) years; 24 males].
  
  
  RESULTS
  Peak systolic blood pressure (177 versus 192 mmHg, p = 0.007), Mets (7.3 versus 9.9, p < 0.001), peak oxygen consumption (VO2max) (29.2 versus 34.5 ml/kg/min, p < 0.001) and peak oxygen pulse (11.0 versus 13.7 ml/beat, p = 0.003) were significantly lower in TOF group versus control. Univariate analyses showed negative correlation between PR fraction and anaerobic threshold. There was a positive correlation between indexed left (LV) and right (RV) ventricular end-diastolic volumes, as well as indexed LV and effective RV stroke volumes, on CMR and VO2max and Mets achieved on CPET. These remained significant after adjustment for age and sex.
  
  
  CONCLUSIONS
  TOF subjects have near normal exercise capacity but significantly lower Mets, VO2max and peak oygen pulse achieved compared to controls. Increased PR fraction in TOF subjects was associated with lower anaerobic threshold. Higher indexed effective RV stroke volume, a measure of LV preload, was associated with higher VO2max and Mets achieved, and may potentially be used as a predictor of exercise capacity.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Yap
authors.forename: Ju Le
authors.initials: JL
authors.lastname: Tan
authors.forename: Thu Thao
authors.initials: TT
authors.lastname: Le
authors.forename: Fei
authors.initials: F
authors.lastname: Gao
authors.forename: Liang
authors.initials: L
authors.lastname: Zhong
authors.forename: Reginald
authors.initials: R
authors.lastname: Liew
authors.forename: Swee Yaw
authors.initials: SY
authors.lastname: Tan
authors.affiliation: Department of Cardiology, National Heart Centre Singapore, 5 Hospital Drive, Singapore 169609, Singapore. tan.ru.san@nhcs.com.sg.
authors.forename: Ru San
authors.initials: RS
authors.lastname: Tan
mesh_terms: D000293:Adolescent; D000328:Adult; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D010101:Oxygen Consumption; D011237:Predictive Value of Tests; D011665:Pulmonary Valve Insufficiency / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D012189:Retrospective Studies; D012846:Singapore; D013771:Tetralogy of Fallot / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right; D055815:Young Adult