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Right Atrial Function is Impaired in Pediatric Pulmonary Arterial Hypertension: A Multi-center Cardiovascular
Kimberley G Miles1, Hieu T Ta1, Kurt R Bjorkman2
1The Heart Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.
Insights
Pediatric pulmonary arterial hypertension (PAH) shows impaired right atrial (RA) function, with dilation and altered phasic function predicting adverse events. Standard cardiovascular magnetic resonance imaging (CMR) reliably assesses these RA changes.
Area of Science:
- Pediatric Cardiology
- Cardiovascular Imaging
- Pulmonary Hypertension Research
Background:
- Impaired right atrial (RA) function predicts adverse outcomes in adults with pulmonary arterial hypertension (PAH).
- RA function in pediatric PAH is not well understood.
- This study investigates RA size and function in pediatric PAH using cardiovascular magnetic resonance imaging (CMR).
Purpose of the Study:
- To analyze RA size and phasic function in pediatric PAH patients.
- To correlate RA metrics with PAH severity.
- To assess the association of RA function with adverse events in pediatric PAH.
Main Methods:
- Retrospective cohort study of pediatric PAH patients and controls using CMR.
- RA volumes and phasic function (total, conduit, active stroke volume, ejection fraction) were measured.
- Novel A/C ratio calculated; correlations with clinical/hemodynamic data and adverse events performed.
Main Results:
- Pediatric PAH patients exhibited larger RA volumes and altered conduit/active phasic function compared to controls.
- RA size and active function correlated with NT-proBNP, RV size, and filling pressures.
- RA conduit ejection fraction and A/C ratio independently predicted adverse events in pediatric PAH.
Conclusions:
- Pediatric PAH involves RA dilation, reduced conduit function, and compensatory increased active function.
- RA size and phasic function assessment via CMR is feasible and reproducible.
- These RA metrics are valuable for assessing PAH severity and predicting outcomes in children.
Background:
Impaired right atrial (RA) function is strongly predictive of adverse outcomes in adults with pulmonary arterial hypertension (PAH) but remains incompletely understood in pediatric PAH. In this pediatric multi-center retrospective cohort study using cardiovascular magnetic resonance imaging (CMR), we analyzed RA size and phasic function and its associations with PAH severity.
Methods:
PAH and control pediatric patients from two centers who underwent CMR from 2010 to 2023 were identified. RA volumes were measured throughout the cardiac cycle using the single-plane, area-length method on a standard 4-chamber cine sequence. Total, conduit phase, and active phase stroke volume (SVi; indexed to BSA) and ejection fraction (EF) were calculated. A novel marker, the A/C ratio, was calculated as active/conduit SVi. RA size and phasic function measurements were correlated with clinical, hemodynamic, and non-RA CMR metrics of PAH severity and were associated with adverse events (Potts shunt, lung transplant listing/surgery, and/or death) using univariate and bivariate Cox proportional-hazards regression analyses. Intra- and inter-rater reliability was analyzed using intra-class correlation coefficients (ICC).
Results:
Compared to controls (n=36), children with PAH (n=72) had higher RA volumes, lower conduit phasic function, and higher active phasic function. In PAH patients, minimum RA volume, active SVi, and A/C ratio directly correlated with NT-proBNP and right ventricular (RV) size, filling pressures, and afterload, while they were inversely correlated with exercise capacity and RVEF. RA conduit EF (cEF) correlations were reversed. During median follow-up of 3.2 years [IQR 1.0, 5.9], RA cEF and A/C ratio remained independent predictors of adverse events after adjustment for common metrics of PAH severity on bivariate analysis, including RVEF (RA cEF aHR 0.91 [95% CI: 0.83-0.99]; A/C ratio aHR 1.58 [95% CI: 1.09-2.29]) and indexed pulmonary vascular resistance (RA cEF aHR 0.83 [95% CI: 0.74-0.93]; A/C ratio aHR 1.79 [95% CI: 1.34-2.41]). RA volume measurements had excellent reliability (ICC >0.97).
Conclusion:
Correlating with disease severity, impaired RA physiology in pediatric PAH is characterized by RA dilation, reduced conduit phasic function, and compensatory augmentation of active phasic function. Assessment of RA size and phasic function is feasible and highly reproducible using standard CMR sequences.
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