Matching Perfusion and Metabolic Activity in HFpEF

This study will test whether Potassium Nitrate (KNO3), with and without Propionyl-L-Carnitine (PLC) and Nicotinamide Riboside (NR), improves submaximal exercise endurance and skeletal muscle oxidative phosphorylation capacity (SkM OxPhos) in participants with Heart Failure with Preserved Ejection Fraction (HFpEF). Additionally, the study will test whether the response to supplemental oxygen during a standardized MRI assessment of skeletal muscle oxidative capacity can identify HFpEF individuals who preferentially will benefit from either KNO3 alone or the combination of pharmacologic agents (KNO3 + PLC + NR)