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Published on: May 11, 2015
The effects of surgically treated pulmonary stenosis on lung growth and cardiopulmonary function in children during
1Dept of Paediatric Respiratory Medicine, The Royal Brompton Hospital, London, UK.
Insights
Pulmonary stenosis (PS) impacts lung development and cardiopulmonary function, even after surgical correction. These subtle but persistent effects in children with PS warrant consideration for treatment timing.
Area of Science:
- Cardiopulmonary Physiology
- Pediatric Cardiology
- Respiratory Medicine
Background:
- The impact of high pulmonary blood flow on lung development is known, but the effects of low flow/pressure remain less understood.
- Pulmonary stenosis (PS) serves as a model to investigate the consequences of reduced pulmonary circulation on lung development and function.
Purpose of the Study:
- To assess the long-term effects of surgically corrected pulmonary stenosis on lung development and cardiopulmonary function in children.
- To evaluate noninvasively the gas exchange and exercise capacity in children with a history of pulmonary stenosis.
Main Methods:
- Noninvasive assessment using mass spectrometry to measure effective pulmonary blood flow, cardiac function, and gas exchange (transfer factor, alveolar ventilation) at rest and during exercise.
- Comparison of 11 children with surgically corrected isolated valvar or subvalvar PS (corrected >10 years prior) against 106 age- and sex-matched healthy controls.
- Calculation of z-scores for study participants based on data from the control group, matched for age, sex, pubertal stage, and body surface area.
Main Results:
- Children with PS exhibited lower forced expiratory volume in one second, cardiac frequency, and transfer constant at rest, with elevated oxygen consumption and arteriovenous oxygen difference (AVO) persisting during exercise.
- During exercise, PS children had slower cardiac frequency and higher AVO compared to controls.
- A greater percentage fall in stroke volume during peak exercise was observed in PS children compared to controls, indicating altered cardiovascular response.
Conclusions:
- Surgically corrected pulmonary stenosis leads to subtle but significant long-term effects on cardiopulmonary function and exercise capacity in children.
- The persistent alterations in gas exchange and cardiovascular response highlight the need to consider these findings when determining the optimal timing for PS treatment.
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 > or =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 x 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 x m(-2)) during exercise led to a reduced transfer constant (0.35 mmol x min(-1) x kPa(-1) x 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.
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