Heart rate and oxygen uptake response to exercise in children with low peak exercise heart rate

Abstract

Normal children achieve the same increase of oxygen uptake (VO2) in response to exercise even though resting and submaximal exercise heart rates vary greatly as a function of age, body size and physical conditioning. To determine whether the VO2 response to exercise is altered when heart rate is significantly reduced by heart disease, we compared 78 children who achieved a peak exercise heart rate of less than or equal to 150 beats/min to 201 controls of similar body size and normal peak exercise heart rates of greater than or equal to 180 beats/min. All performed incremental (16.4 Watts/min) maximal cycle exercise. Separate analysis of males and females included heart rate, power (kg-m/min, Watts/kg), VO2 (ml/min, ml/min per kg), O2 pulse (VO2/heart beat), VE (l/min) and R (VCO2/VO2) at rest and during the 1st, 4th and last minute of exercise. Patients with low peak exercise heart rates had also lower resting submaximal exercise heart rates than controls. VO2 at comparable exercise levels did not differ from controls and consequently O2 pulse was greater in the patients than controls at rest and at all levels of exercise. A consistent gender difference was only found in controls where males achieved a higher VO2 and lower heart rates at comparable levels of exercise. The data show a normal exercise VO2 despite significantly lower heart rates. These findings cannot be explained by an increased arteriovenous difference alone and suggest that the patients retained the ability to effectively modulate stroke volume.

Exercise Studies in Tetralogy of Fallot: A Review

“…The reduced heart rate response contributes to the reduced VO 2max in these patients. However, low submaximal heart rates have little effect on submaximal VO 2 , which is usually normal, a finding consistent with a recent comparison of patients with markedly reduced maximal heart rates (ഛ150 beats/min) to patients with a normal heart rate response to exercise [75]. It should be noted that performance indices which are based on regressing heart rate on work rate, such as the W170 (power at a heart rate of 170 beats/min), tend to overestimate work capacity in the presence of a reduced heart rate response to exercise and should therefore not be used in tetralogy patients [10,52,91].…”

Exercise Studies in Patients with Transposition of the Great Arteries After Atrial Repair Operations (Mustard/Senning): A Review

“…Although the sinus node artery and/or damage to specialized intraatrial conduction tracts have been implicated in the heart rate and arrhythmia issues [46], additional factors such as altered cardiovascular/pulmonary reflexes may well be involved considering that low maximal heart rates are also observed in adult heart disease [16] and after operations for other congenital heart lesions [45].…”

Normal values for cardiopulmonary exercise testing in children

“…39 When data from earlier publications were compared with ours, values for HR reserve and VO 2peak were comparable. 7,27,28 …”

“…A somewhat lower HR peak does not invalidate the exercise parameters obtained in a child. Schulze-Neck et al 28 found that VO 2peak /kg values were comparable in children who achieved a HR peak greater than 180 bpm compared with children with a HR peak lower than 180 bpm.…”