Exercise induces significant biventricular intraventricular mechanical dyssynchrony in children with TOF

  • Dr Lucy Roche, The Hospital for Sick Children, Toronto, Canada
  • Dr Lars Grosse-Wortmann, The Hospital for Sick Children, Toronto, Canada
  • Dr Paul Kantor, The Hospital for Sick Children, Toronto, Canada
  • Dr Andrew Redington, The Hopsital for Sick Children, Toronto, Canada
  • Dr Mark Friedberg, The Hosiptal for Sick Children, Toronto, Canada

    • Objective:
    To investigate the effect of exercise on right (RV) and left (LV) intraventricular dyssynchrony and their relation to ventricular function and exercise capacity in children with repaired tetralogy of Fallot (TOF).

    Methods:
    We prospectively studied 29 children with TOF with echocardiography at rest and at peak exercise, MRI and metabolic exercise testing. Dyssynchrony results were compared with healthy controls at rest (n=42) and peak bicycle ergometry (n=25)

    LV dyssynchrony index (LVDI) was assessed by tissue Doppler imaging (TDI) of apical 4-, 3- and 2-chamber views and the SD of time to peak S velocity in 12 LV segments calculated.

    RV dyssynchrony index (RVDI) was assessed by TDI of apical 4-chamber and RVOT views and the SD of time to peak S velocity in 8 RV segments calculated.
    All indices were corrected for heart rate.

    Results:
    Controls and patients with TOF were of similar age and had similar dyssynchrony indices at rest (table). There were marked differences in their response to exercise (figure). In contrast to controls, exercise caused increasing LVDI and RVDI in children with TOF.

    Although the exercise capacity of those with TOF was impaired, (mean peak VO2=63% predicted) this was unassociated with the degree of either LVDI or RVDI on exertion (LVDI r=0.04 p=NS, RVDI r=0.23 p=NS). LVDI and RVDI were not related to LVEF (r=0.08 p=NS) or RVEF (r=0.29 p=NS).

    Conclusion:
    Exercise induces significant LV and RV intraventricular mechanical dyssynchrony in children with TOF although this alone does not account for their impaired exercise capacity.

    Controls Children with TOF p value
    Age at study (years) 12.4 12.2 0.82
    Mean resting LV dyssynchrony index (HR corrected) 33.9 38.6 0.16
    Mean resting RV dyssynchrony index (HR corrected) 43.6 37.7 0.03
    Mean exercise LV dyssynchrony index (HR corrected) 33.1 49.6 0.002
    Mean exercise RV dyssynchrony index (HR corrected) 26.1 61.1 <0.0001