Figure 2.

Left ventricular end-systolic elastance was calculated by using the single-beat method. These echocardiographic scans display the evaluation of ejection fraction (left image) and preejection and ejection time (right image) using aortic Doppler waveforms. Normalized ventricular elastance at arterial end-diastole (End) was measured according to the following formula: $\begin{array}{l}{\mathit{E}}_{\mathit{es}\left(\mathit{sb}\right)}\mathit{=}\left[{\mathit{P}}_{\mathit{d}}\mathit{-}\left({\mathit{E}}_{\mathit{Nd}\left(\mathit{est}\right)}\mathit{\times }{\mathit{P}}_{\mathit{s}}\mathit{\times }\mathit{0.9}\right)\right]\mathit{/}\mathit{[}\mathit{SV}\mathit{\times }{\mathit{E}}_{\mathit{Nd}\left(\mathit{est}\right)}\mathit{]}\\ {\mathit{E}}_{\mathit{Nd}\left(\mathit{avg}\right)}\mathit{=}\mathit{\Sigma }{\mathit{a}}_{\mathit{i}}\mathit{\times }{\mathit{t}}_{\mathit{Nd}}\\ \mathit{i}\mathit{=}\mathit{0}\\ {\mathit{E}}_{\mathit{Nd}\left(\mathit{est}\right)}\mathit{=}\mathit{0.0275}\mathit{–}\mathit{0.165}\mathit{\times }\mathit{EF}\mathit{+}\mathit{0.3656}\mathit{\times }\left({\mathit{P}}_{\mathit{d}}\mathit{/}{\mathit{P}}_{\mathit{es}}\right)\mathit{+}\mathit{0.515}\mathit{\times }{\mathit{E}}_{\mathit{Nd}\left(\mathit{avg}\right)}\end{array}$ where a_i values are 0.35695, -7.2266, 74.249, -307.39, 684.54. -856.92, 571.95 and -159.1 for i = 1 to i = 7, respectively. The value t_Nd value was determined by the ratio of pre-ejection period (R-wave to flow onset) to total systolic period (R-wave to end-flow), with the time of onset and termination of flow-defined Doppler. Systolic blood pressure and diastolic blood pressure were measured invasively. The single-beat method used to calculate left ventricular end-systolic elastance was previously validated by Chen et al. [8].