Single-beat estimation of end-systolic elastance using bilinearly approximated time-varying elastance curve

Background-Although left ventricular end-systolic elastance (E-es) has often been used as an index of contractility, technical difficulties in measuring volume and in changing loading conditions have made its clinical application somewhat limited. By approximating the time-varying elastance curve by 2 linear functions (isovolumic contraction phase and ejection phase) and estimating the slope ratio of these, we developed a method to estimate E-es on a single-beat basis from pressure values, systolic time intervals, and stroke volume. Methods and Results-In 11 anesthetized dogs, we compared single-beat E-es with that obtained with caval occlusion. Although the decrease (but not the increase) in contractility (5.3 to 11.4 mm Hg/mL) and the change in loading conditions (3.7 to 34.0 mm Hg/mL) over wide ranges significantly altered the slope ratio, the estimation of E-es was reasonably accurate (y=0.97x+0.46, r=0.929, SEE=2.1 mm Hg/mL). Conclusions-E-es can be estimated on a single-beat basis from easily obtainable variables by approximating the time-varying elastance curve by a bilinear function.