Dynamics of respiratory gas exchange during exercise after
correction of congenital heart disease.
Reybrouck, Tony, Luc Mertens, Neale Kalis, Maria Weymans, Monique
Dumoulin, Wim Daenen, Marc Gewillig.
Departments of Cardiorespiratory Rehabilitation, Pediatric
Cardiology and Cardiac Surgery, Gasthuisberg University Hospital,
University of Leuven, 3000 Leuven, Belgium
APStracts 2:0427A, 1995.
In pediatric exercise testing, conventional measures of aerobic
exercise function such as O2 max or the ventilatory anaerobic
threshold (VAT) use only one value for the assessment of exercise
capacity. We studied a more comprehensive approach to evaluate
aerobic exercise function by analysing the steepness of the slope of
CO2 vs O2 above the VAT (S3). This was calculated in 32 patients
operated for congenital heart disease [16 for transposition of the
great arteries (TGA); 16 for tetralogy of Fallot (TF)] and was
compared to 16 age-matched controls (nl). The results show that the
reproducibility of this new assessment method was excellent
(coefficient of variation for S3 : 8.6 %). S3 was significantly
steeper (p < 0.05) in the patients (1.31 +/- 0.22 for TGA and
1.28 +/- 0.16 for TF) compared to the nl (1.10 +/- 0.22). Also the
difference between S3-S1 was significantly higher in the patients
(0.37 +/- 0.22 for TGA and 0.31 +/- 0.10 for TF) than in controls
(0.22 +/- 0.06). The steeper slopes were associated with lower than
normal values for VAT and O2 during exercise. It is concluded that
the analysis of the steepness of the slope of CO2 is a sensitive,
reproducible and objective approach to evaluate the integrative
cardiopulmonary response to exercise. It complements the assessment
of a subnormal VAT by reflecting the extent of anaerobic metabolism.
Received 12 December 1994; accepted in final form 14 September
1995.
APS Manuscript Number A1260-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95