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 Reybrouck1,21Department 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 paperBackground: 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