Increased right atrial volume measured with cardiac magnetic resonance is associated with worse clinical outcome in patients with pre-capillary pulmonary hypertension

Aims: Pre-capillary pulmonary hypertension (PH_pre-cap) has a poor prognosis, especially when caused by pulmonary arterial hypertension (PAH) associated with systemic sclerosis (SSc-PAH). Whether cardiac magnetic resonance (CMR)-based quantification of atrial volumes in PH_pre-cap is beneficial in risk assessment is unknown. The aims were to investigate if (i) atrial volumes using CMR are associated with death or lung transplantation in PH_pre-cap, (ii) atrial volumes differ among four unmatched major PH_pre-cap subgroups, and (iii) atrial volumes differ between SSc-PAH and idiopathic/familial PAH (IPAH/FPAH) when matched for pulmonary vascular resistance (PVR). Methods and results: Seventy-five PH_pre-cap patients (57 ± 19 years, 53 female, 43 de novo) with CMR and right heart catheterization were retrospectively included. Short-axis stacks of cine images were analysed, and right and left atrial maximum (RAV_max and LAV_max) and minimum volume (RAV_min and LAV_min) were indexed for body surface area. Increased (mean + 2 SD) and reduced (mean – 2 SD) volumes were predefined from CMR normal values. Transplantation-free survival was lower in patients with increased RAV_max than in those with normal [hazard ratio (HR) = 2.1, 95% confidence interval (CI) 1.1–4.0] but did not differ between those with reduced LAV_max and normal (HR 2.0, 95% CI 0.8–5.1). RAV_max and RAV_min showed no differences among unmatched or matched groups (P = ns). When matched for PVR, LAV_max, LAV_min, and pulmonary artery wedge pressure were reduced in SSc-PAH compared with IPAH/FPAH (95% CI 0.3–21.4, 95% CI 0.8–19.6, and 95% CI 2–7, respectively). Conclusions: Patients with PH_pre-cap and increased right atrial volume measured with CMR had worse clinical outcome. When matched for PVR, left atrial volume was lower in SSc-PAH than in IPAH/FPAH, consistent with left-sided underfilling, indicating a potential differentiator between the groups.