The Effects of Disease and Treatments on Ventriculo-Arterial Coupling: Implications for Long-term Care

Abstract

Left ventricular (LV) function can be described by its pressure-volume trajectory during one cardiac cycle, with volume on the x-axis (Fig. 12.1). This LV pressure-volume representation is extremely informative of most of the determinants of LV function, describing the four phases of the cardiac cycle: diastolic filling, isovolumic contraction, ejection and isovolumic relaxation. Each pressure-volume loop defines the systolic and diastolic limits of LV pressure and volume independent of preload or afterload. LV pressure-volume points cannot exist outside the limits of diastolic compliance and the end-systolic elastance, defined as the LV end-systolic pressure-volume relationship (ESPVR), which is mostly linear over the physiologic range with a negative slope and a positive zero pressure volume intercept. The ESPVR defines the maximal LV systolic stiffness and is thus also called end-systolic elastance (Ees). At the other extreme, the end-diastolic pressure-volume relationship (EDPVR), reflecting global LV diastolic compliance is slightly curvilinear becoming steeper (stiffer) as LV volumes become large. Important to this discussion, the LV ESPVR reflects global LV systolic function, with increasing and decreasing Ees reflecting increasing and decreasing LV contractility, respectively; whereas EDPVR represents LV diastolic properties.