Abstract 17218: Reduced Left Atrial Compliance in Heart Failure With Preserved Ejection Fraction: New Insights Into Pathophysiology

Background: Reduced left atrial (LA) compliance (LAC) contributes to pulmonary venous hypertension in heart failure with preserved ejection fraction (HFpEF); however the underlying mechanisms are poorly defined. We hypothesized that microvascular inflammation with rarefaction and impaired nitric oxide (NO) signaling, LA titin hypophosphorylation and fibrosis may each contribute to reduced LAC in HFpEF. Methods: Invasive LA pressure-volume (PV) analyses (open-chest; pericardiotomy; admittance catheter) were performed in 9 aged dogs with experimental hypertension (bilateral renal wrap + DOCA; HFpEF) compared to 13 sham-operated young adult dogs (control). LAC was measured at end-LA reservoir during acute preload reduction (cava occlusion). LA tissue and LA microvascular function were analyzed. Results: Compared to controls, the curvilinear end-LA reservoir PV relationship (Fig A) was shifted upward/leftward in HFpEF (LA diastolic stiffness constant 0.08 vs 0.16 mmHg/mL in controls, p=0.005). LA microvascula...