Pulmonary Artery Relative Area Change Detects Mild Elevations in Pulmonary Vascular Resistance and Predicts Adverse Outcome in Pulmonary Hypertension

Objective: The aim of this study was to evaluate the clinical use of magnetic resonance imaging measurements related to pulmonary artery stiffness in the evaluation of pulmonary hypertension (PH). Materials and Methods: A total of 134 patients with suspected PH underwent right heart catheterization (RHC) and magnetic resonance imaging on a 1.5-T scanner within 2 days. Phase contrast imaging at the pulmonary artery trunk and cine cardiac views were acquired. Pulmonary artery area change (AC), relative AC (RAC), compliance (AC/pulse pressure from RHC), distensibility (RAC/pulse pressure from RHC), right ventricular functional indices, and right ventricular mass were all derived. Regression curve fitting identified the statistical model of best fit between RHC measurements and pulmonary artery stiffness indices. The diagnostic accuracy and prognostic value of noninvasive AC and RAC were also assessed. Results: The relationship between pulmonary vascular resistance and pulmonary artery RAC was best reflected by an inverse linear model. Patients with mild elevation in pulmonary vascular resistance (<4 Woods units) demonstrated reduced RAC (P = 0.02) and increased right ventricular mass index (P < 0.0001) without significant loss of right ventricular function (P = 0.17). At follow-up of 0 to 40 months, 18 patients with PH had died (16%). Analysis of Kaplan-Meier plots showed that both AC and RAC predicted mortality (log-rank test, P = 0.046 and P = 0.012, respectively). Area change and RAC were also predictors of mortality using univariate Cox proportional hazards regression analysis (P = 0.046 and P = 0.03, respectively). Conclusions: Noninvasive assessment of pulmonary artery RAC is a marker sensitive to early increased vascular resistance in PH and is a predictor of adverse outcome.