Pulmonary arterial compliance in children with atrial and ventricular septal defect

Previous studies have documented the normal values of pulmonary arterial compliance (Cp) in animals and adult humans. In the past, variations in Cp and its measurement in children with septal defects has been unknown. In the present study, we found the Windkessel model, which uses compliance and resistance as parameters, to be a useful tool in understanding Cp in pediatric patients. Calculations of Cp were based on the pulmonary arterial diastolic pressure waveform as an exponential function of time. First, Cp was estimated by studying pressure tracings of the main pulmonary artery (MPA) obtained from both routine cardiac catheterization and pressure measured by a catheter-tip manometer, which was performed during a catheterization study of seven children with various congenital heart diseases. Second, 124 children with atrial and ventricular septal defects aged between 45 days and 12 years were studied using the data obtained from routine catheterization. Hemodynamic data were used to calculate pulmonary vascular resistance (Rp), pulmonary arterial time constant (Tp) and Cp. A strong correlation (r = 0.954) was found in the Cp value estimated by data obtained from routine catheterization and from the catheter-tip manometer study. The present study shows an estimated mean (SEM) Cp in normal children of 1.53 (0.17) ml/mmHg per m2. The estimated mean (SEM) Cp was 1.91 (0.10) and 1.70 (0.11) ml/mmHg per m2 in children with atrial septal defect (ASD) and ventricular septal defect (VSD), respectively. It was found that Cp was significantly (P = 0.04) higher in female patients with a VSD. Also, a significantly low Cp (0.95 ± 0.06 ml/mmHg per m2) was observed in patients with a VSD and pulmonary hypertension (VSDPH). In conclusion, Cp was calculated by the exponential decay portion of the MPA diastolic pressure waveform. A normal Cp value was observed in ASD and VSD patients and a significantly low Cp was observed in children with a VSDPH. Cp was higher in female VSD patients than in male VSD patients.