FIGURE 4.

Ventriculo-Arterial (VA) coupling (Ea/Ees) is a measure of mechanical efficiency of heart performance and vascular load function to deliver sufficient O₂ to the tissues (Monge Garcia et al., 2020). The function of the arterial system is determined by the relationship between the stroke volume (SV) and end-systolic arterial pressure, where higher SVs lead to higher arterial end-systolic pressures (London, 2005; Yurdagul et al., 2016; Axell et al., 2017). The slope of this relationship is termed arterial elastance (Ea), which describes the capability of the arterial vessels to increase pressure when SV increases. Ea is estimated as 0.9 times the brachial systolic pressure divided by SV. Ees is a measure of cardiac contractility and can be determined non-invasively using routine echocardiography (Guarracino et al., 2013). It is a load-independent index of left ventricular (LV) chamber performance, which is influenced by wall stiffness, fibrosis, contraction synchrony and geometric LV chamber dimensions. When Ea/Ees ∼1.0, the efficiency of the system is optimal, meaning that the left ventricle is providing sufficient SV at its lowest possible myocardial energy consumption. The advantage of VA coupling over ejection fraction (EF) or cardiac output (CO) is that it provides additional information on arterial loading and left ventricular function to potentially guide treatments.