Peak oxygen uptake in heart failure. Look behind the number!
An impaired peak oxygen uptake (V̇O2peak) during a maximal cardiopulmonary exercise test (CPET) has been shown extensively to correlate with a poor prognosis in heart failure (HF) patients. Even, the abovementioned relationship remains effective irrespective of the left ventricular ejection fraction (LVEF), a most recent study by Sato showing an unaltered V̇O2peak prognostic power also in the early defined HF with mid-range ejection fraction class (HFmrEF). The advantage of adopting V̇O2peak to evaluate and, possibly, to manage clinically this setting of patients is linked to its composite character which enables it to account for most of the mechanisms underlying the HF pathophysiology. In fact, as per the well-known Fick Law, V̇O2 represents arithmetically the resulting number of the product between cardiac output (CO = stroke volume*heart rate) and artero-venous O2 difference (ΔavO2). Thus, a reduced V̇O2peak, as a single variable, mirrors variably a reduced LVEF and/or a concomitant chronotropic incompetence as well as a huge number of conditions able to impact negatively on the O2 transport and delivery