Determinants of the dimension of pulmonary artery in patients with pulmonary arterial hypertension

Abstract Background the dilation of the pulmonary artery (PA) is a possible complication in patients with pulmonary arterial hypertension (PAH). The literature contains limited and conflicting data on what influences PA dilation. Purpose to investigate the clinical and haemodynamic determinants of PA diameter, the ratio between the pulmonary artery and the ascending aorta (PA/Ao ratio) and their changes during follow-up. Methods all patients with PAH with at least one available pulmonary CT scan performed within 6 months from diagnostic right heart catheterization (RHC) and referred to a single centre were included. The last available angio-CT scan was considered to evaluate the PA diameter and the PA/Ao ratio velocity increase. We performed a univariate linear regression analysis both at baseline assessment and at follow-up to determine the predictors of PA dimension and its increase over time. The variables tested were: age, sex, disease aetiology, FC-WHO, six-minute walking distance (6MWD), brain natriuretic peptide/N-terminal prohormone of brain natriuretic peptide (BNP/NT-proBNP), heart rate, right atrial pressure, pulmonary arterial pressures, pulmonary capillary wedge pressure, cardiac output, cardiac index, pulmonary vascular resistance, pulmonary arterial compliance, SvO2, French Pulmonary Hypertension Registry risk calculator, and COMPERA risk calculator. All these variables were assessed at the initial evaluation and at follow-up, and also their changes over time were evaluated. Variables with a p-value below 0.1 were included in the multivariate model. Additionally, we performed a ROC (Receiver Operating Characteristic) analysis to determine the mPAP value with the best predictive ability for both PA diameter and PA/Ao increase. Results we enrolled 754 patients. At baseline assessment, patients with PAH presented a dilated PA (35 IQR 32-39 mm) with an annual growth rate of 0.34 mm IQR 0-0.85. The results of the multivariate analysis are summarized in the figure below (figure 1). A mPAP value 35 mmHg best predicts PA increase (AUC area under the curve 0.6183) and PA/Ao increase (AUC 0.6344). Conclusion mPAP is an independent determinant of PA diameter, PA/Ao ratio (both at baseline and at follow-up), as well as of their change over time. ΔPAC is inversely correlated with the growth over time of both PA and the PA/Ao ratio. The persistence of a mPAP above 35 mmHg is the best predictor of PA dilatation over time.