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Exercise induces biventricular mechanical dyssynchrony in children with repaired tetralogy of Fallot
  1. S Lucy Roche,
  2. Lars Grosse-Wortmann,
  3. Andrew N Redington,
  4. Cameron Slorach,
  5. Gareth Smith,
  6. Paul F Kantor,
  7. Mark K Friedberg
  1. The Labatt Family Heart Center, The Hospital for Sick Children, Toronto, Ontario, Canada
  1. Correspondence to Dr Mark Friedberg, Division of Cardiology, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada; mark.friedberg{at}


Objective The mechanisms underlying adverse electro-mechanical interaction after tetralogy of Fallot (TOF) repair remain unclear. This study investigated biventricular dyssynchrony in children with TOF and its relationship to exercise, QRS duration (QRSd) and ventricular mechanics.

Methods 29 asymptomatic children (5–18 years) with repaired TOF were prospectively evaluated by MRI, cardiopulmonary exercise testing and echocardiography at rest and during bicycle exertion. Their dyssynchrony results were compared with those of 44 resting and 27 exercising, age- and sex-matched controls. An intraventricular dyssynchrony index was calculated from the SD of regional time intervals in 12 left ventricular (LV) ‘Ts LV-12SD’ and eight right ventricular (RV) ‘Ts RV-8SD’ segments. Ventricular size, volumes, ejection fractions, pulmonary regurgitant volumes and peak oxygen consumption and N-terminal BNP levels were quantified in the patients.

Results Despite moderate RV dilatation (median indexed RV end-diastolic volume 145.2 ml/m2) and right bundle branch block (median QRSd 130 ms) compared with controls, children with TOF demonstrated neither RV nor LV dyssynchrony at rest (Ts RV-8SD, 37.9±10.2 vs 44.3±10.3, 95% CI −11.8 to −0.99, p=0.02; Ts LV-12SD, 38.6±16.8 vs 34.0±10.8, 95% CI −1.8 to 11.0, p=0.16). Exercise stress induced biventricular dyssynchrony in patients with TOF but not in controls (Ts RV-8SD, 59.9±34.4 vs 28.2±10.4, p<0.0001, 95% CI 17.2 to 46.3; Ts LV-12SD, 48.0±18.6 vs 31.9±10.7, 95% CI 7.9 to 24.4, p=0.002). This was unrelated to QRSd, ventricular volumes and function, or peak oxygen consumption.

Conclusion Exercise induces biventricular mechanical dyssynchrony in children with TOF.

  • Paediatric cardiology
  • Fallot's tetralogy
  • echocardiography-exercise

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  • Funding This project was supported by a SickKids Foundation grant (The Hospital for Sick Children, Toronto) and the Canadian Institutes of Health Research. SLR received support from the Philip Witchel Heart Failure Research Fellowship (The Hospital for Sick Children, Toronto) and the British Congenital Cardiac Association's Madeleine Steel Fellowship.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the the Research Ethics Board at The Hospital for Sick Children, Toronto.

  • Provenance and peer review Not commissioned; externally peer reviewed.