Right atrial stiffness index predicts mortality in pulmonary hypertension when standard atrial metrics fail
C Kocx, T Barlow, A Pearlman, S Lal, D S CelermajerAbstract
Background
Right atrial (RA) remodelling is a hallmark of pulmonary hypertension (PH), yet standard echocardiographic metrics such as RA area and reservoir strain have inconsistent prognostic value in treated cohorts. We hypothesised that indexing atrial deformation to haemodynamic load, coupling the RA with the RV and PA (yielding an RA Stiffness Index) would unmask prognostically relevant diastolic dysfunction missed by conventional assessment.
Methods
We retrospectively analysed echocardiographic assessments of 47 consecutive patients with confirmed PH (94% on established pulmonary vasodilator therapy). RA Stiffness Index was calculated as the ratio of echocardiographic pulmonary artery systolic pressure to RA reservoir strain (ePASP/RASr). The index was calculable in 40 patients (85%); 7 patients were excluded due to unquantifiable tricuspid regurgitation velocity (n=5) or inadequate RA strain tracking (n=2). Cox proportional hazards regression assessed the association between imaging parameters and all-cause mortality, with Kaplan-Meier analysis for visual representation.
Results
Over a median follow-up of 2.9 years, 16 patients (34%) died. Standard RA metrics failed to predict mortality: neither RA area (HR 1.06 per cm²; 95% CI 0.98–1.13; p=0.13) nor RA reservoir strain (HR 0.98 per %; 95% CI 0.93–1.02; p=0.31) reached significance. In contrast, RA Stiffness Index was significantly associated with death as a continuous variable (HR 1.14 per unit increase; 95% CI 1.01–1.27; p=0.027)—each unit increase in stiffness conferred a 14% increase in mortality risk. Kaplan-Meier analysis demonstrated divergent survival curves when dichotomised by median stiffness (1.9 mmHg/%), with 3-year survival of 93% in the low-stiffness group versus 74% in the high-stiffness group (Figure). The log-rank test did not reach conventional significance (p=0.12), reflecting expected loss of statistical efficiency when a continuous predictor is dichotomised.
Conclusion
In PH patients on established therapy, RA Stiffness Index (a load-adjusted measure of atrial compliance) predicts mortality when standard geometric and deformation metrics do not. The significant continuous association, supported by visually divergent survival curves, suggests this index identifies high-risk diastolic phenotypes missed by conventional assessment. Validation in larger cohorts and correlation with invasive haemodynamics are warranted.For image description, please refer to the figure legend and surrounding text.