Abstract Body (Do not enter title and authors here): BACKGROUND
Compared to our understanding of left ventricular (LV) dysfunction in cardiac aging, there is far less depiction of right heart function, especially right ventricular (RV) remodelling in response to pulmonary arterial (PA) changes with aging. Given the importance of cardio-respiratory function in declining aerobic capacity with age, identifying sensitive metrics of RV function would complete our understanding of RV and RV-PA conduit adaptations in aging.

METHODS
Community older adults without cardiovascular disease underwent prospective cardiac magnetic resonance (CMR) imaging that measured RV volumes (RV end-diastolic volume, EDV; end-systolic volume, ESV), RV function (RV ejection fraction, RVEF; RV global longitudinal strain, GLS) and RV-PA coupling (end-systolic elastance to arterial elastance, computed as ratio of LV stroke volume, SV to RVESV). A RV-PA coupling threshold of >1.5 (based on prior literature) implies effective RV adaptation Aerobic capacity (VO₂) was calculated. Multivariable regression adjusted for significant covariates.

RESULTS
We studied 251 participants (54.5% female, 70.78±9.07 years) with normal LV and RV function (mean LVEF, 65.13±7.51 %, RVEF, 64.25±6.98 %). RV-PA threshold of <1.5 defined poorer RV structure and function with lower RVEF (56.6 ± 3.95 vs. 67.5 ± 5.25, p < 0.001), RVGLS (28.13± 4.55 vs. 32.8 ± 5.1, p = 0.0065) and higher RVEDV index (73.2 ± 15.15 vs. 63.34 ± 12.03, p < 0.001), compared to those with RVPA > 1.5. Predictors of better RVGLS were female sex (β=0.189, adj. p=0.019), independent of systolic and diastolic blood pressure while predictors of RVESV were female sex (β=-0.433, adj. p<0.00), age (β=-0.195, adj. p<0.001) and body mass index (β=0.264, adj. p<0.001). Overall, women had better RVEF and RVGLS but lower RVSV and VO₂ (30.1±4,5 vs 37.7±5.1, ml/kg/min) compared to men (all p<0.001) (Table 1). Lower VO₂ among women compared to men was accompanied by higher RV-PA (2.1±0.7 vs 1.8±0.7, p<0.001). Female sex (β=0.233, 95% CI [0.158, 0.506, adj. p<0.001) was independently associated with RV-PA coupling on multivariable analyses.

CONCLUSIONS
Novel CMR-derived right heart parameters defined RV function and RV adaptations as depicted by RV-PA interactions in older adults. Superior RV functions and RV-PA coupling in women may represent hemodynamic adaptations in women, despite lower aerobic capacities.