Relationship between pulmonary arterial resistance and compliance among patients with pulmonary arterial hypertension and congenital heart disease

Abstract

BackgroundIt is unknown whether changes in pulmonary arterial resistance (Rp), pulmonary arterial compliance (Cp), and the product of Rp and Cp (the RC time) in patients with pulmonary arterial hypertension (PAH) are related to an increase in pulmonary blood flow. The aim of this study is to clarify relationships between these parameters before and after corrective surgery among patients with PAH and congenital heart disease. MethodsWe performed cardiac catheter examinations and compared Rp, Cp, and the RC time before and after corrective surgery in 100 infants (53 boys) with PAH related to ventricular septal defect. ResultsMedian age at surgery was 2.9 (0.6-28.5) months. Preoperative values of the ratio of pulmonary to systemic blood flow (Qp/Qs), systolic pulmonary arterial pressure (PAP), Rp, Cp, and the RC time were 3.5 (2.7-4.3), 65 (56-70) mm Hg, 2.18 (1.64-3.19) Wood unit/m2, 2.67 (2.01-3.38) mL/mm Hg/m2, and 0.36 (0.31-0.40) seconds, respectively. Postoperative systolic PAP, Cp, and the RC time were significantly decreased to 26 (23-29) mm Hg, 1.96 (1.77-2.26) mL/mm Hg/m2, and 0.31 (0.26-0.36) seconds, respectively, although Rp remained unchanged at 2.53 (2.06-3.31) Wood unit/m2. The relationship between Rp and Cp was inversely related before and after surgery, and the Rp-Cp coupling curve was shifted downward after surgery. In addition, lower preoperative Cp (partial regression coefficient = −3.35; P = .001) and preterm delivery (partial regression coefficient = 6.28; P = .02) were independently related to postoperative higher systolic PAP. ConclusionsRp-Cp coupling depends on both the amount of pulmonary blood flow and the condition of the pulmonary vasculature. Lower preoperative Cp is an independent predictive factor to predict higher postoperative pulmonary systolic pressure leading to an increase in right ventricular workload. It is necessary to assess Rp-Cp coupling before surgery among patients with PAH related to congenital heart disease.