Abstract 11168: Right Atrial Adaptation in Pulmonary Hypertension: In-Depth Pressure-Volume Analysis

Introduction: Pulmonary hypertension (PH) is associated with increased right atrial (RA) pressure and volume. We hypothesized that RA stroke work and RA stiffness are higher in PH patients in comparison to healthy controls. Methods: RA PV loops were created through a novel method. RA volume was measured throughout the cardiac cycle on a magnetic resonance transverse stack of slices (typically 8-10). RA pressure was averaged over at least 10 cardiac cycles and approximately two respiratory cycles. Alignment of RA volume and pressure was done based on the v-wave (peak during ventricular contraction, see figure). RA stroke work was calculated as the area under the PV loop from the p-wave (start of atrial contraction) to the minimal RA volume. RA active emptying as the difference between p-wave and minimal volume. An exponential curve was fitted through the reservoir portion of the PV loop from the x-descent to the v-wave. The slope of this curve at the v-wave (RA end-reservoir elastance) was determined as a measure of RA stiffness. Results: RA PV loops were created for healthy controls (n=9) and PH patients (n=27). The averaged PV loops in the figure show RA dilatation in PH patients as well as elevated pressure, especially during atrial contraction. The difference between RA maximal pressure and p-wave pressure was higher in PH patients in comparison with controls (4.01 [3.12-6.75] vs 2.83 [2.54-3.06] mmHg; p=0.001). RA stroke work (493±253 vs 171±50 mmHg*ml; p=0.001) and active emptying (41±13 vs 23±5 ml; p<0.001) were also higher in PH, while RA end-reservoir elastance was not (0.26 [0.23-0.37] vs 0.33 [0.24-0.64] mmHg/ml; p=0.22). Conclusions: PH patients have increased RA stroke work and active emptying, as assessed with a novel method to derive RA PV loops. They do not show signs of RA stiffening. Future associations with right ventricular diastolic stiffness will show whether RA stroke work is able to match the increase in RA afterload.