Left ventricular-arterial coupling in septic shock: A physiological review

Conventional modeling of cardiovascular function prioritizes the interplay between cardiac contractility and venous return curves as primary determinants of stroke volume. However, this approach does not capture the influence of arterial load in flow generation, thus hindering a more comprehensive understanding of macrovascular dynamics. Since both heart and arteries are elastic chambers with distinctive geometries housing blood volume, their coupling could be derived from pressure-volume curves, which ultimately denote time-varying elastance relationships. Accordingly, the left ventricular-arterial coupling (LVAC), represented by the ratio between arterial and ventricular elastances, could indirectly estimate the energy transmission from the heart to the proximal arterial tree, thus reflecting cardiovascular efficiency. Assessment of LVAC by combining bedside echocardiography and arterial pressure monitoring may improve the understanding of macrohemodynamics during shock conditions and might potentially help to evaluate the impact of cardiovascular therapies. Nevertheless, cardiovascular dysfunction in septic shock result from complex interactions and highly variable degrees of hypovolemia, pathological vasodilation, peripheral vascular decoupling, microvascular blood flow misdistribution, and heart-pump dysfunction, whereby optimizing LVAC during the resuscitation process would not necessarily reverse tissue hypoperfusion. This review provides an analysis of the components of LVAC, including the physiological fundamentals of arterial and ventricular elastances, explores its relationship with cardiovascular efficiency and energetics, synthesizes available data about LVAC assessment in septic shock, addresses some unresolved controversies, and proposes a conceptual framework for future research.