Response of the oxygen pulse during exercise in children with atrial repair for transposition of the great arteries

Roselien Buys,^1,2,* Kimberly Dockx,^1,* Marc Gewillig,³ Tony Reybrouck<sup>1,2

1</sup>Department of Rehabilitation Sciences, ²Department of Cardiovascular Rehabilitation, University of Leuven, Leuven, Belgium; ³Department of Pediatric Cardiology, University Hospital Gasthuisberg, Leuven, Belgium

*These authors contributed equally to this paper


Background: The oxygen pulse equals stroke volume times arterial–venous oxygen difference and is calculated by dividing oxygen uptake (VO₂) by heart rate (HR). In children with a Senning repair for the transposition of the great arteries (TGA), the response of both HR and VO₂ to exercise is impaired. Our aim was to assess the oxygen pulse response during exercise in patients who underwent a Senning operation, comparing it with healthy controls.
Methods: Twenty-one children with a Senning repair (mean age 12.5 ± 1.7 years) and a control group of 31 healthy children (mean age 13.2 ± 2.0 years) performed a graded maximal exercise test on a treadmill, during which HR and VO₂ were measured. Oxygen pulse was calculated by dividing VO₂ by HR. Right ventricular function was quantitatively assessed by cardiac ultrasound.
Results: Senning patients had a lower peak oxygen pulse than the control (P = 0.0024) (8.45 ± 1.90 mL • beats^-1 versus 11.7 ± 3.93 mL • beats^-1), as with the peak VO₂ (P < 0.001) (35.8 ± 5.67 mL • min^-1 • kg^-1 versus 46.6 ± 8.02 mL • min^-1 • kg^-1) and peak HR (171 ± 14 beats • min^-1 versus 188 ± 11 beats • min^-1). During submaximal exercise, oxygen pulse and VO₂ were also significantly lower in Senning patients when compared to the control group (P = 0.027). In seven Senning patients (33%), the oxygen pulse did not increase any further after the first exercise levels. These patients had lower right ventricular function compared to the control group (P = 0.04).
Conclusion: Children with a Senning repair for TGA have a reduced peak VO₂, peak HR, and peak oxygen pulse. Their oxygen pulse starts off at a lower level, reaches its plateau earlier, and is related to right ventricular function. This variable can be considered a complementary parameter to assess cardiovascular exercise performance.

Keywords: transposition of the great arteries, Senning repair, oxygen pulse, cardiopulmonary exercise testing