Ejection fraction as a determinant of elastance measures in the pressure volume relationship

Computational methods are described to predict end-systolic volume (ESV) and end-systolic pressure (ESP) as components of the datapoints forming the end-systolic pressure volume relationship (ESPVR). Presented methods are based on stroke volume (SV) and stroke pressure (SP) as coupling quantities between the ventricle and the conduit. Based on SV and SP, we compute the ESPVR first beat slope (E beat 1 slope) based on ejection fraction (EF) and the elastance of ventricle–arterial coupling (Evac = SP/SV). The E beat 1 slope result is then interpreted as the initial tangent condition for a quadratic Bezier curve construction to approximate the ESPVR data of subsequent preload-adjusted beats. To assess curve approximation accuracy, we analyzed 36 pressure volume (PV) loop sequences to compute ESPVR slopes defining end-systolic elastance (Ees). Similar slope computations were then performed to calculate corresponding end-systolic elastic slope estimates (Ees’) from curve data. Comparing Ees measures to Ees’ estimates through the upper half and lower half ranges of the ESPVR dynamic pressure range, comparison results by linear regression were (1) upper range Ees’ = 0.95 × Ees + 0.01 mmHg/ml (R2 = 0.97) and (2) lower range Ees’ = 0.62 × Ees + 0.20 mmHg/ml (R2 = 0.75). These findings suggest that the application of formative E beat 1 slope constraints can provide robust estimates of ESPVR at natural functioning pressures and plausibly highlight physiological mechanisms forming the ESPVR data trend.