Noninvasive estimation of right atrial pressure using magnetic resonance imaging: a development and validation study

Background Right atrial pressure (RAP) is a key determinant of right-sided heart function and guides diagnosis and management across a wide range of cardiovascular diseases. However, reliable noninvasive estimation remains difficult. Purpose We aimed to develop and externally validate an MRI-based model for predicting invasive RAP. Methods This study included 181 adults (median age 60 years; median RAP 7 mmHg) who underwent clinically indicated MRI and right heart catheterization within 48 hours between 2016-2025. Indications included heart transplantation surveillance (67.4%), pulmonary hypertension (16.6%), dilated cardiomyopathy (11.6%), and constrictive pericarditis (4.4%). The sample was randomly split into a development (n=125) and held-out test cohort (n=56) stratified by RAP category. Generalized additive models and systematic transformation screening were used to characterize nonlinear predictor-outcome associations. Predictors were selected using predefined criteria (ΔAIC≥2, partial R² ≥0.02, LASSO bootstrap inclusion ≥60%, physiological plausibility). Results The final model included inferior vena cava (IVC) expiratory diameter (linear and quadratic terms), liver T1 relaxation time (linear and quadratic terms), RA area (linear), and body weight (linear) (Figure 1A). In the development cohort, performance was strong (R² 0.698; residual standard deviation 2.58 mmHg) and robust across repeated 10-fold cross-validation (50 repetitions), leave-one-out cross-validation, and bootstrap optimism correction (Figure 1B). In the external test cohort, performance remained consistent (R² 0.621; root-mean-square error 2.78 mmHg; mean absolute error 2.07 mmHg; concordance coefficient 0.777). Calibration in the testing set was excellent (intercept +0.18, slope 0.92; integrated calibration index 0.65 mmHg). Discrimination for elevated RAP was high with AUCs of 0.749 (>5 mmHg), 0.949 (>10 mmHg), and 0.965 (>15 mmHg) (Figure 2). Conclusions An MRI model incorporating abdominal venous and hepatic tissue biomarkers provides a clinically useful, well-calibrated approach for estimating invasive RAP.Figure 1Figure 2