0598 Nocturnal Hypoxia and Right Ventricular Functional Characteristics in Connective Tissue Disease Associated Group 1 Pulmonary Arterial Hypertension
Authors: Lowery Megan , Wang Lu , Jellis Christine , Kwon Deborah , Hill Nicholas , Mehra Reena 
Published: May 2022

Abstract

Introduction
We extend our prior findings of nocturnal hypoxia association with right ventricular(RV) dysfunction in World Symposium Pulmonary Hypertension(WSPH) Group 1 Pulmonary Arterial Hypertension(PAH) to connective tissue disease(CTD)-PAH. Due to the autoimmune inflammatory pathophysiology in CTD, we postulate stronger associations with nocturnal hypoxia and RV dysfunction in CTD-PAH with less favorable transplant-free survival than non-CTD-PAH.

Methods
The multicenter PVDOMICS study(NCT02989887) includes Group 1 PAH patients &gt;18 years with mean pulmonary artery pressure≥25mmHg, pulmonary capillary wedge pressure(PCWP) £15mmHg, and pulmonary vascular resistance &gt;3 Woods units who underwent NOX-T3 home sleep study or other sleep testing within one year of enrollment. Linear regression models(beta coefficients,95%CI) were used to examine total recording time&lt;90% SaO2(T90) with right ventricular(RV) functional measures: RV systolic pressure(RVSP,echocardiogram,mmHg), RV ejection fraction(RVEF, cardiac magnetic resonance imaging,%). Time-to-event analysis was performed examining T90 with transplant/death using Cox proportional hazard models in CTD-PAH and non-CTD-PAH. T90 interaction by CTD-PAH group was tested. Models were adjusted for age, sex, race, body mass index, PAH medications and supplemental oxygen/positive airway pressure.

Results
The analytic sample was comprised of CTD-PAH(n=45: 59.3±12.1 years,82.2% female) and non-CTD-PAH patients(n=142: 50.4 + 14.1,68.3% female). For each increase in T90 by 10%, RVSP increased 2.57mmHg(2.57[0.76, 4.38],p=0.006) and RVEF decreased 1.54%(-1.54[-2.58, -0.50],p=0.004) in CTD-PAH. For each increase in T90 by 10% in non-CTD-PAH, RVSP increased 2.34mmHg(2.34[1.30, 3.38],p&lt;0.001) and RVEF decreased 0.72%(-0.72[-1.31,-0.13],p=0.017). The test for statistical interaction was not significant across CTD-PAH and non-CTD-PAH groups. There was similar mortality rates between CTD-PAH(22%) and non-CTD-PAH(24%). However, T90 was only associated with death/transplant in non-CTD-PAH with a 24% increased risk of transplant/death(HR=1.24, 95%CI:1.08-1.43,p=0.003). There was a borderline statistically significant interaction across groups in time-to-event analyses(p=0.092).

Conclusion
We identify that nocturnal hypoxia is associated with RV functional alterations irrespective of CTD contribution in Group 1 PAH after adjustment for confounding factors. Survival analyses demonstrated an association of the degree of nocturnal hypoxia and transplant/death only in the non-CTD-PAH group. Potential explanations for these unanticipated findings may be attributable to lower sample size of the CTD-PAH group or a true stronger hypoxia-mortality relationship driven by underlying pathophysiology of the non-CTD-PAH group.

Support (If Any)
NHLBI(U01HL125218,U01HL125205,U01HL125212,U01HL125208,U01HL125175, U01HL125215,U01HL125177); Pulmonary Hypertension Association