Passive Elasticity of the Human Left Ventricle

Abstract

Pressure-volume (PV) and stress-strain relationships (a-e) were utilized for evaluation of stiffness changes in the human left ventricle. A total of 45 patients were studied with data available from routine cardiac catheterization. They were divided into eight groups from which five were chosen for statistical comparison. These were the groups of normal, idiopathic hypertrophy without obstruction (IH), congestive heart failure in severe coronary artery disease (CHF-CAD,), moderate to severe CAD2, and mild to moderate CAD3.Utilizing precise pressure volume relationships, the natural elastic stiffness (da80./dE2) for a spherical model and the stiffness constant K2 were evaluated. In addition, stress-strain relationships for ellipsoid model were utilized for evaluation of the diastolic stiffness and the stiffness constants bi and K3 as obtained for the modified Lagrangian strain (L-L,)/L, and the natural strain Loge(L/Lo), respectively. The constants K2, b, and K3 were 20.3 + 1.5, 15.0 ± 2.4 and 15.8 + 2.3 for eight normal patients; 34.5 ± 7.9, 18.3 + 3.4 and 19.0 + 3.5 for seven patients with idiopathic hypertrophy; 101.2 ± 24.2, 61.0 ± 13.0 and 62.3 + 13.0 for six patients with severe CAD and CHF (CHF-CAD1); Several methods have been employed for analysis of left ventricular diastolic con;pliance or elasticity. Some of them related simple pressure difference to volume difference AP/zV or z1V/AP.4 5 It was soon 609

Muscle stiffness determined from canine left ventricular pressure-volume curves.

“…To date, however, the relationship between these indexes of the ventricular pressure-volume curve and the stiffness of the muscle itself remains cloudy. For example, there is not yet agreement on the question of whether changes in the diastolic pressure-volume curve that accompany disease arise from changes in the elasticity of the muscle itself (1)(2)(3)(4), geometric effects associated with hypertrophy or dilation (5,6), or other mechanisms (7). These controversies arise because of a lack of an experimentally validated and logically derived equation describing the ventricular pressurevolume relationship in terms of the muscle's nonlinear elasticity.…”

“…where (3) and p, V, and h equal ventricular pressure, volume, and wall thickness, respectively. To compare the stiffness parameter, /3, computed to fit ventricular pressure-volume curves and muscle stress-strain curves, one must replace the extension, x -x*, with the Lagrangian strain, e = (xx*)/x*, and use the normalized stiffness fi* = fix*.…”

Asymptotic slope of log pressure vs log volume as an approximate index of the diastolic elastic properties of the myocardium in man.

“…The pressure-volume data below a pressure of 3 mm Hg were not incorporated in the curve-fit and subsequent analysis by Fester 17 The straight line is the visually estimated asymptotic slope, m = 4.94. The slope calculated from curve-fit parameters17 was m = 4.10.…”

The regional elastic properties analysis of myocardium based on echocardiographic 3-D reconstruction of the left ventricle

“…As is well known, myocardium contractility is closely related to the passive properties of cardiac muscle (Dumesnil and Shoucri 1991;Fester and Samet 1974;Guccione et al 1991;King et al 1995). To assess intact left ventricle (LV) performance, indirect indices of diastolic myocardium stiffness (e.g., end diastolic pressure) were widely introduced in clinical investigations (Guccione et al 1991).…”

“…A number of studies attempted to estimate the myocardium regional elastic properties during the LV diastolic filling phase (Azhari et al 1990;Fester and Samet 1974;Guccione et al 1991;Omens et al 1993;Sys and Brutsaert 1989) on the basis of relative thickness change: ⌬HWT ϭ (HWT 1 Ϫ HWT 2 )/HWT 1 , where HWT 1 , HWT 2 are the values of heart wall region thickness corresponding to the beginning and the end of diastole. While filling, the LV can be considered as a passive structure, and the wall thickness changing depends only on the chamber blood pressure and myocardium elastic properties.…”