In Vivo Pressure-Radius Relationships of the Pulmonary Artery in Children with Congenital Heart Disease

The effects of either increased pulmonary artery blood flow or pressure on the magnitude of the radius and the dynamic properties of the right pulmonary artery were studied angiographically in 162 patients during cardiac catheterization. Patients were divided into seven groups according to their hemodynamic findings. The right pulmonary artery radius was measured during systole and diastole, from the projected films, at the midpoint between the bifurcation of the main pulmonary artery and the bifurcation of the right pulmonary artery. The mean pulmonary artery radius was increased in patients with either increased pulmonary blood flow or pressure, and in patients with isolated valvular pulmonic stenosis. Both the pressure-strain elastic modulus (stiffness index) and the tension-radius regression were different from normal only in patients with increased pulmonary artery pressure regardless of the pulmonary blood flow. This finding indicates that the pulmonary artery is stiffer in patients with pulmonary hypertension but that its elastic properties are not altered secondarily to increased blood flow.