Abstract 4142444: The Effect of Left Atrial Filling Pressure on Exercise Arterial Oxygenation in HFpEF: Does the V-wave matter?

Background: Left atrial (LA) myopathy is common in patients with heart failure with preserved ejection fraction (HFpEF) and is characterized by decreased LA compliance, pulmonary vascular dysfunction, and decreased survival. However, the mechanistic relationship between these variables are unclear. It has been thought pulmonary capillary wedge pressure (PCWP), particularly the v-wave which is directly transmitted backwards into the pulmonary circulation, contributes to worsened pulmonary vascular function through disruption of lung diffusion of oxygen. Though efforts to reduce PCWP, such as with interatrial shunt devices, have not improved outcomes. We hypothesized that HFpEF patients with greater v-wave amplitudes would have worse pulmonary gas exchange assessed by lower arterial partial pressure of oxygen (PaO2) but that reductions in the v-wave amplitude would not improve arterial gas exchange. Methods: Patients with HFpEF underwent upright invasive hemodynamic exercise testing with right heart and radial arterial catheterizations. PCWP tracings and arterial blood gases were obtained during rest and submaximal 20W exercise without (control: con) and with nitroglycerin (NTG) on a semi-recumbent cycle. V-wave peaks were measured manually by two observers (blinded). Results: In 40 patients with HFpEF, mean v-wave amplitudes at rest were 9.9 ± 4.4 mmHg (con) and 9.4 ± 4.0 mmHg (NTG; p=0.33) and during 20W exercise were 27 ± 15 mmHg (con) and 22 ± 9.9 mmHg (NTG; p=0.018). PaO2 at rest was 86 ± 12 mmHg (con) and 82 ± 10 mmHg (NTG) and during 20W exercise was 85 ± 13 mmHg for both control and NTG. PaO2 was negatively correlated with v-wave amplitude across all conditions (figure) but increases in v-wave amplitude from rest to 20W exercise did not correlate with changes in PaO2 under either condition (control: p = 0.49, R^2 = 0.013; NTG: p = 0.55, R^2 = 0.0093). Similarly, reductions in v-wave with NTG did not improve PaO2 at rest or with 20W exercise. Conclusions: While higher v-wave amplitudes correlated with a lower PaO2, changes in v-wave amplitude, whether via increases through exercise or decreases with NTG, had no effect on arterial oxygenation. These results suggest that elevated v-waves may not play a role in decreasing PaO2.