Randomised, controlled trial on fluid restriction in pulmonary arterial hypertension.

INTRODUCTION: The objective of this study was to analyse the influence of fluid restriction (FR) on right heart size and clinical parameters in pulmonary arterial hypertension (PAH) patients with right heart failure (RHF). METHODS: In this prospective, single-centre, randomised, controlled study (Trial Registration: DRKS00029667), PAH patients with RHF and signs of volume overload were included. Intensified instructions for restriction of fluid intake to ≈1.5 l/d were compared to routine recommendation of FR. The primary endpoint was the change in right atrial (RA) and right ventricular (RV) area at follow-up. Secondary endpoints included haemodynamics, quality of life, symptoms and physical capacity. RESULTS: Overall, 41 PAH patients were included (70.2±12.0 years; 51.2% male; 70.7% WHO functional class III). During follow-up (mean 28.0±6.4 weeks) both groups showed comparable fluid intake reduction (intervention -0.56±0.51 l/d; control -0.57±0.71 l/d; all -0.57±0.60 l/d; p<0.001) with a significant improvement of the primary endpoint RA area (mean reduction -2.09±5.88 cm²; p=0.049) but not RV area (-1.12±4.48 cm²; p=0.160). Among secondary endpoints systolic pulmonary arterial pressure (sPAP, -7.90±14.68 mmHg; p=0.005), left ventricular eccentricity index (LV-EI, -0.09±0.22; p=0.020), mental health (6.67±18.57; p=0.047), physical function (8.03±20.04; p=0.028) and symptom burden (PAH-SYMPACT -4.33±10.23; p=0.021) improved significantly. CONCLUSION: The results of this controlled, prospective study demonstrate that FR to ≈1.5 l/d can significantly improve RA size and important clinical parameters in PAH patients as sPAP, LV-EI and quality of life. Notably, routine clinical counselling alone was sufficient to achieve effective fluid restriction, with no additional benefit observed from an intensified educational intervention.