Pulmonary arterial compliance in children with atrial and ventricular septal defect.

Thesis Report.

Abstract:

Background: previous studies have documented the normal values of pulmonary arterial compliance (Cp) in animals and adult human beings. However, a limited number of such studies have been performed in patients with cardiac septal defects. The objectives of this study were to determine the normal reference value of Cp in children and its changes in atrial septal defects (ASD), ventricular septal defects (VSD) and ventricular septal defects with pulmonary hypertension (VSDPH) by utilizing pulmonary arterial resistance (Rp) and pulmonary arterial time constant (Tp).

Methods: Cp was calculated based on the pulmonary arterial diastolic pressure waveform minus the left atrial pressure difference as an exponential function of time. First, Cp was estimated by studying the main pulmonary artererial pressure (MPAP) waveform obtained from both routine cardiac catheterization and the pressure measured by a cather-tip-manometer, which was performed during the catheterization study of 7 children with various congenital heart diseases. Secondly, 124 children with attial and ventricular septal defects between 45 days and 12 years of age were studied using the data obtained from the routine catheterization. Hemodynamic data were utilized to calculate the Rp, Tp and Cp.

Results: A strong correlation (r=0.954) was found in the Cp value estimated by data obtained from the routine catheterization and from the catheter-tip manometer study. A strong relationship (r=0.879) between the Cp estimated by previous method and the new method was also found. This study showed an estimated normal children's mea (SEM) Cp at 1053 (0.17) ml mm Hg-1m-2. The estimated Cp was 1.91 (0.10) and 1.70 (0.11) in ASD and VSD patients, respectively. It was found that Cp was significantly (p=0.004) higher in female patients with a VSD. Also, a significantly low Cp, 0.95 (0.06) ml mm Hg-1 m-2, was observed in patients with a VSDPH. In 3 patients with VSDPH associated with physiologically insignificant minor anomalies, Cp changed from a low value to normal range (1.18-1.88 ml mm Hg-1m-2) after surgical repair of VSD.

Conclusion: A normal Cp value was estimated in children. A significantly low Cp was observed in patients with a VSDPH indicating low expansibility. Cp was higher in females than males in VSD patients. MPAP wave from obtained from routine cardiac catheterization can be utilized to estimate the Cp in children with atrial and ventricular septal defect. Cp may be useful for the early recognition of the pulmonary hypertension in postoperative patients with septal defects.