The effects of surgically treated pulmonary stenosis on lung growth and cardiopulmonary function in children during rest and exercise

Abstract

The effects of high pulmonary blood flow and pressure on pulmonary development are well understood, but the effect of low pulmonary flow/pressure is not. Pulmonary stenosis (PS) was therefore used as a model to determine its effect on lung development, which was assessed noninvasively by carbon monoxide transfer at rest and during exercise. One hundred and six control children (55 males, 8-16 yrs) and 11 children with isolated valvar or subvalvar PS surgically corrected ≥10 yrs prior to the study without residual stenosis/regurgitation were evaluated. Measurements of effective pulmonary blood flow, stroke volume, arteriovenous oxygen difference (AVO), transfer factor and transfer constant, alveolar ventilation and anaerobic threshold were performed using a mass spectrometer. Data from the normal children allowed calculation of z-scores for the study group matched for age, sex, pubertal stage and surface area. PS children at rest had a significantly lower forced expired volume in one second, cardiac frequency and transfer constant with a raised oxygen consumption and AVO which persisted on exercise. During exercise, the cardiac frequency was 12 beats·min-1 slower and AVO 0.017 L greater than controls (p<0.05). A persistently mildly raised effective functional residual capacity (0.2 L·m-2) during exercise led to a reduced transfer constant (0.35 mmol·min-1·kPa-1·L-1), although the percentage rise (28%) from rest to peak exercise was normal. The percentage fall in stroke volume from the penultimate exercise stage to peak exercise stage was greater in PS children (24%, 95% confidence interval 11- 37) than control children (2.4, -2-10, p<0.005). In conclusion, although the effects are small, pulmonary stenosis does affect cardiopulmonary function after surgery. This needs to be considered when contemplating the timing of treatment.