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Background In contrast to the considerable literature on the prognostic value of right ventricular metrics at baseline and follow-up in PAH, the prognostic value of right atrial size and function has been less well studied. The aim of this study was to compare the prognostic value of right atrial length, area and volume measurements in treatment naive patients with PAH and the impact of treatment. Methods Patients with PAH who underwent MRI at baseline and follow up on a 1.5 T MRI scanner were identified. Maximum and minimum right atrial length, area and volume were measured on two and four chamber images. Survival analysis, using univariate and multivariate Cox proportional hazards regression analysis was performed. Results 154 patients were identified, of whom 18 died. Change in minimal right atrial volume predicted mortality (p=0.028). Change in maximal right atrial volume, stroke volume and ejection fraction did not predict mortality, p=0.228, p=0.229 and p=0.915 respectively. Other than change in minimum two chamber right atrial area predicting mortality (p=0.049), individual changes in length and area measurements in the 4 chamber images were not prognostic. Right atrial length and area measures were highly reproducible intraclass correlation coefficient 0.910 to 0.984. Conclusion Change in minimal right atrial volume predicts mortality and maybe of value in the serial evaluation of patients on PAH therapy.

Introduction: Pulmonary arterial hypertension is defined at cardiac catheterization as a mPAP≥ 25 mmHg and a pulmonary arterial wedge pressure (PAWP) ≤15mmHg. The presence of cardiac comorbidities is associated with a poorer response to therapy in patients with PAH and left ventricular diastolic dysfunction may exist even in the presence of a normal resting PAWP. The aim of this study was to use left atrial volume as a surrogate of left ventricular diastolic dysfunction in patients with normal PAWP and assess its impact on treatment response in PAH. Methods: We studied 85 treatment naive patients with PAH with an MRI at baseline and follow up at 1 year (median 1year IQR 0.8). Patients were grouped by LA volume threshold of 34ml/m2 based on established literature. Changes in biventricular volume, mass and function were compared. Results: Compared to patients with elevated LA volume (n=31), those with normal LA volume (n=54) had greater treatment response with increase in change in RV ejection fraction, LV stroke volume, LV end diastolic volume and diastolic interventricular septal angle (p=0.032, p=0.001, p=0.001 and p=0.025 respectively). Patients with normal LA volume had a significant improvement in RV ejection fraction between baseline and follow up (mean increase 9%, p Conclusion: This study shows that in patients meeting the haemodynamic criteria for PAH, patients with an elevated LA volume had poor response to PAH therapy. Further work to better characterize this PAH phenotype and recognize the importance of comorbidities in predicting response to therapy is required.

Quantitative magnetic resonance imaging provides a comprehensive and non-invasive assessment of the heart and lungs in patients with suspected pulmonary hypertension with the potential for accurate assessment of disease severity and response to treatment. Magnetic resonance imaging (MRI) can provide detailed reliable information of heart structure and function as the heart responds to elevated right ventricle afterload in patients with progressive pulmonary vascular disease; notably, progressive changes in right ventricle volume and function are of prognostic value independent of established biomarkers. This article reviews the current literature on MRI in pulmonary hypertension and also describes new and exciting developments in imaging of the heart, pulmonary vasculature and lungs, including assessment of myocardial changes with late gadolinium-enhanced imaging and T1 mapping, evaluating changes in the proximal pulmonary vasculature using image-based computational modelling and quantitative assessment of the capillary bed using MRI perfusion analysis.