LAUSR

BACKGROUND Recent studies show adverse right atrial (RA) emptying pattern is prognostic for clinical worsening events in pediatric pulmonary arterial hypertension (PAH). No study has reported changes in RA emptying over time or evaluated whether serial measurements offer further prognostic information. METHODS Prospective study of 32 children with idiopathic or heritable PAH undergoing echocardiogram at baseline and 1-year. RA conduit fraction percent (RA cF%) was measured as percentage of total diastolic RA area change prior to the electrical p wave. Clinical worsening was analyzed with a predefined composite adverse event outcome. RESULTS Longitudinal subjects (median age 13.3 yr) had RA cF% 61% (IQR 32-68%) at baseline and 60% (IQR 35-73%) at 1-year (NS). 11 subjects had a qualifying event during median 21-month follow-up. Subjects with an event had 1-year RA cF% = 33% (IQR 20-40%) compared to 72% (IQR 63-75%) for those with no event (p < 0.001). Event rates were lowest for subjects with both echocardiograms showing RA cF% > 60% (0%), highest for subjects with neither (80%), and intermediate for those with one (38%, p = 0.003). CONCLUSIONS Changes in RA cF% inform risk of adverse events in pediatric PAH. This finding supports the role of RA cF% as both a prognostic biomarker and potential treatment target.