Cardiac MRI right atrial area measurement thresholds for risk stratification in patients with PAH

Introduction: The ESC/ERS guidelines provide right atrial (RA) maximal area prognostic thresholds for patients with pulmonary arterial hypertension (PAH) and indicate they can be applied to cardiac magnetic resonance imaging (cMRI); however, they have not been validated. The aim of this study was to validate these prognostic thresholds and derive thresholds for alternative RA area measurements. Methods: Consecutive patients with PAH were identified between April 2012 and March 2017 from the ASPIRE registry. Patients underwent baseline and follow-up cMRI. Thresholds were identified using LOESS analysis for 1-year mortality at follow-up and their prognostic significance assessed using Kaplan-Meier analysis. Results: During the follow-up period of 24 (mean 12, SD 5) months 226 patients with PAH were identified, 72 patients (32%) died overall and 20 patients (9%) died at 1-year. RA maximum area thresholds identified by LOESS analysis were 25cm2 at low, intermediate and high-risk (log rank 13.96, p=0.001). Similarly, the ERS/ESC thresholds identified patients at low, intermediate and high-risk (log rank 13.82, p=0.001). RA minimum area thresholds were >10cm2, 10-16cm2 and 38% at low, intermediate and high-risk (log rank 15.15, p=0.001). However, the ERS/ESC and LOESS analysis thresholds did not show significant difference between the low and intermediate risk groups. Conclusions: This study identifies optimal right atrial thresholds for low, intermediate and high risk of mortality at 1-year using cMRI.