A fast computational model for circulatory dynamics: effects of left ventricle-aorta coupling

Evaluation of vascular aging on measures of cardiac function and mechanical efficiency: insights from in-silico modeling

Introduction

This study evaluated the hypothesis that vascular aging (VA) reduces ventricular contractile function and mechanical efficiency (ME) using the left ventricular pressure-volume (PV) construct.

Methods

A previously published in-silico computational model (CM) was modified to evaluate the hypothesis in two phases. In phase I, the CM included five settings of aortic compliance (CA) from normal to stiff, studied at a heart rate of 80 bpm, and phase II included the normal to stiff CA settings evaluated at 60, 100, and 140 bpm. The PV construct provided steady-state and transient data through a simulated vena caval occlusion (VCO). The steady-state data included left ventricular volumes (EDV and ESV), stroke work (SW), and VCO provided the PV area (PVA) data in addition to the three measures of contractile state (CS): end-systolic pressure-volume relationship (ESPVR), dP/dtmax-EDV and preload recruitable stroke work (PRSW). Finally, ME was calculated with the SW/PVA parameter.

Results

In phase I, EDV and ESV increased, as did SW and PVA. The impact on the CS parameters demonstrated a small decrease in ESPVR, no change in dP/dtmax-EDV, and a large increase in PRSW. ME decreased from 71.5 to 60.8%, respectively. In phase II, at the normal and stiff CA settings, across the heart rates studied, EDV and ESV decreased, ESPVR and dP/dtmax-EDV increased and PRSW decreased. ME decreased from 76.4 to 62.6% at the normal CA and 65.8 to 53.2% at the stiff CA.

Discussion

The CM generated new insights regarding how the VA process impacts the contractile state of the myocardium and ME.

Evaluation of ventricular-vascular coupling with critical care metrics: An in silico approach

Mean arterial pressure and cardiac output provide insufficient guidance for the management of intraoperative hypotension (IOH). In silico models offer additional insights into acute changes in hemodynamic parameters that may be encountered during IOH. A computational model (CM) generated parameters quantifying ventricular-vascular coupling, and pressure-volume construct across levels of aortic compliance (CA ). We studied how a loss from normal-to-stiff CA impacts critical care metrics of hemodynamics during vascular occlusion. Pulse pressure (PP), end-systolic pressure (Pes ), arterial compliance (Art-ca), arterial elastance (Art-ea), and dynamic arterial elastance (Eadyn), along mechanical efficiency (ME) were measured at five levels of CA . A loss in CA impacted all variables. During steady-state conditions, PP, Pes , and stroke work increased significantly as CA decreased. Art-ca decreased and Art-ea increased similarly; Eadyn increased and ME decreased. During a decrease in preload across all CA levels, arterial dynamics measures remained linear. The CM demonstrated that a loss in CA impacts measures of arterial dynamics during steady-state and transient conditions and the model demonstrates that critical care metrics are sensitive to changes in CA . While Art-ca and Art-ea were sensitive to changes in preload, Eadyn did not change.