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The pulmonary vascular response to oxygen and its influence on operative results in children with ventricular septal
Insights
Preoperative oxygen responsiveness in children with ventricular septal defects does not predict surgical outcomes. Children with Down syndrome showed a greater pulmonary vascular resistance decrease with oxygen.
Area of Science:
- Pediatric Cardiology
- Pulmonary Hypertension
- Congenital Heart Disease
Background:
- Children with large ventricular septal defects (VSDs) often have elevated pulmonary vascular resistance (PVR).
- Assessing pulmonary vascular responsiveness to oxygen preoperatively is crucial for surgical planning.
Purpose of the Study:
- To evaluate the predictive value of preoperative pulmonary vascular responsiveness to oxygen in children with large VSDs and elevated PVR.
- To compare oxygen responsiveness between children with and without Down syndrome.
Main Methods:
- Measured pulmonary-to-systemic resistance ratio (Rp/Rs) before and after oxygen inhalation in 25 children with large VSDs.
- Defined a positive response as a ≥30% fall in Rp/Rs.
- Compared outcomes and restudied hemodynamics post-VSD closure.
Main Results:
- Children with Down syndrome exhibited a significantly greater Rp/Rs fall (52%) compared to those without (31%).
- Preoperative oxygen responsiveness did not predict operative survival or postoperative PVR.
- Post-VSD closure, PVR decreased in both oxygen responders and non-responders.
Conclusions:
- Preoperative pulmonary vascular responsiveness to oxygen is not a reliable predictor of surgical outcomes in pediatric VSD.
- Down syndrome may be associated with distinct pulmonary vascular responses in VSD.
- Further research is needed to understand long-term PVR changes post-VSD closure.
Abstract:
The ratio of pulmonary vascular resistance to systemic resistance was determined before and after oxygen administration in 25 children with an isolated large ventricular septal defect and elevated pulmonary vascular resistance (pulmonary/systemic resistance ratio, Rp/Rs greater than 0.25). A fall of 30% or more in the Rp/Rs, after 20 minutes of oxygen inhalation (FiO2 greater than 0.90), was considered a positive response to oxygen. In the 6 children with Down's syndrome, the Rp/Rs fell significantly more in oxygen (52%) than it did in the 19 children without Down's syndrome (31%, p less than 0.05). No other clinical or baseline hemodynamic finding was predictive of vascular responsiveness. Seventeen children underwent closure of the ventricular septal defect. Three of 11 children who responded to O2 expired shortly after operation; each of the 6 children who did not respond to O2 survived operation. Two of the deaths (occurring less than 12 hours after closure) were from low cardiac output; a third child died suddenly 5 days postoperatively. Thirteen children, 7 who responded to oxygen and 6 who did not, were restudied by cardiac catheterization an average of 2.0 years following successful closure of the ventricular septal defect. While the Rp/Rs in room air fell following closure of the defect in both groups, the decrease was 22% in responders and 28% in nonresponders. The results of this study, unlike similar studies performed at higher altitudes, suggest that the preoperative responsiveness of the pulmonary vasculature to oxygen does not predict either operative survival or postoperative pulmonary vascular resistance.