A Mechanical Model of the Human Heart Relating Septal Function to Myocardial Work and Energy

Abstract

A thorough understanding of ventricular interaction and the effects of septal function on right and left ventricular performance in the human heart requires measurement of interventricular pressure gradients using high fidelity pressure transducers. The advent of newer echocardiographic techniques provides an opportunity to combine high resolution images with bi-ventricular catheterization data in the cardiac catheterization laboratory, and obtain the detailed hemodynamic and echocardiographic information necessary to more fully understand the clinical manifestations of normal and abnormal septal and free wall mechanical function. We have anticipated these developments and modified the description of heart mechanics in our integrated multi-scale model of the human cardio-respiratory system (H-CRS) to closely analyze how the mechanical properties of the inter-ventricular septum affect the work, energy utilization, and oxygen consumption of the atria, ventricles, septum, and each ventricular free wall. Combined with the H-CRS model, these modifications allow one to observe how tissue properties of the septum affect the entire heart and circulation. For example, the normal septum transfers energy from the left to the right ventricle, and assists the pre-load of both, acting as a third pump. Diseases that increase septal elastance cause abnormalities resembling left ventricular diastolic dysfunction (LVDD), including a decrease in cardiac output and an increase in pulmonary pressures despite a normal left ventricular ejection fraction. Similar applications of the H-CRS model to other regional disorders such as hypertrophic obstructive cardiomyopathy and myocardial infarction might likewise allow one to study their clinical implications in greater detail.

Modeling study of the failing heart and its interaction with an implantable rotary blood pump

“…6C, black line) decreases by 97%. RV performance as demonstrated by previous work [5–6] is highly dependent on septal contribution particularly during ejection. With septal work at nearly zero, RV work rises.…”

“…5). A positive slope in V SPT indicates rightward movement, whereas a negative slope indicates leftward movement [5]. With LVSD, the septum is rightward bowed through most of diastole due to the characteristically enlarged LV.…”

“…With LVSD, the septum is rightward bowed through most of diastole due to the characteristically enlarged LV. Septal priming, or the sharp rightward movement at early systole, which aids RV ejection [5]-[6] disappears (Fig. 5C).…”

“…The role and effectiveness of the iRBP can be evaluated through an analysis of total heart work and the contribution of individual elements to work [5]. As shown in Table I, total heart work diminishes with the iRBP in place and at increasing speeds.…”

Decision-making in advanced heart failure patients requiring LVAD insertion: Can preoperative simulation become the way forward? A case study

“…[20] A linear model remains sufficiently accurate [21][22][23] and adequate in order to simulate the PV relationship, [24] although cardiovascular multiscale modelling [25] has confirmed the limitations of the time-varying elastance concept in relation to the load-dependence of the end-systolic pressure-volume relationship (ESPVR) highlighting the role of further modelling techniques. [26][27][28][29] To address these shortcomings, a nonlinear time-varying theory [30] with modifications including the inter-ventricular septum and a continuous flow pump [31] is appropriate. Here a unimodal function represents the ESPVR and the Frank-Starling law, making it suitable for the analysis of ventricular interactions with LVAD.…”