Visual Abstract
Highlights • ΔAVo2 during exercise is a complex metric that incorporates into its calculation skeletal muscle blood flow and DmO2 across the skeletal muscle capillary membrane. • Although ΔAVo2 was reduced in patients with HFpEF during both systemic and local (forearm) exercise, there was no difference in forearm DmO2 among subjects with HFpEF, those with hypertension, and healthy control subjects; therefore, abnormalities in forearm DmO2 cannot explain the reduced forearm ΔAVo2 seen in subjects with HFpEF. • Local forearm exercise performance predicted about one-third of the variability in systemic aerobic capacity, demonstrating that peripheral factors are important in determining whole-body exercise tolerance. • Degree of adiposity strongly correlated with ΔAVo2 during both local and whole-body exercise, suggesting that adipose tissue may play an active role in limiting exercise capacity in subjects with HFpEF.
Summary The aim of this study was to determine the arteriovenous oxygen content difference (ΔAVo2) in adult subjects with and without heart failure with preserved ejection fraction (HFpEF) during systemic and forearm exercise. Subjects with HFpEF had reduced ΔAVo2. Forearm diffusional conductance for oxygen, a lumped conductance parameter that incorporates all impediments to the movement of oxygen from red blood cells in skeletal muscle capillaries into the mitochondria within myocytes, was estimated. Forearm diffusional conductance for oxygen was not different among adults with HFpEF, those with hypertension, and healthy control subjects; therefore, diffusional conductance cannot explain the reduced forearm ΔAVo2. Instead, adiposity was strongly associated with ΔAVo2, suggesting an active role for adipose tissue in reducing exercise capacity in patients with HFpEF.