Abstract
In this study, we have tried to understand why the left ventricle (LV) is not a homogeneous sphere. An experimental model of a spherical ventricle was developed. The chamber was configured as a mathematical model, and the wall properties were represented by isolated cardiac muscles. The stroke work of the spherical LV when modelling different types of inhomogeneity in the wall structure was investigated. It was found that the emergence of even slight inhomogeneity in a spherical ventricle inevitably results in a diminution of pump function. It was concluded that at a given level of the myocardial contractility, a homogeneous spherical LV would not have any functional reserve, ie no ability to maintain pump function in case of additional load. Functional reserve can be achieved only with a certain degree of inhomogeneity. Thus, inhomogeneity in the normal left ventricular wall structure constitutes a strategic functional reserve that is absent in a homogeneous spherical ventricle.
Highlights
The normal left ventricle (LV) is a structurally inhomogeneous pump according to factors such as its geometry (Lessick et al 1996), the intricacy of the muscular fibre architecture (Streeter et al 1969, 1973), and the peculiarities of the myocardial blood supply and conduction systems (Scher 1953; Arisi et al 1983)
Inhomogeneity is known to be an indispensable attribute of the normal LV (Barletta et al 1998; Bogaert and Rademakers 2001); the significance of inhomogeneity for the normal heart has not yet been clarified
To simulate to some extent the inhomogeneity in a spherical LV wall we developed an experimental model
Summary
The normal left ventricle (LV) is a structurally inhomogeneous pump according to factors such as its geometry (Lessick et al 1996), the intricacy of the muscular fibre architecture (Streeter et al 1969, 1973), and the peculiarities of the myocardial blood supply and conduction systems (Scher 1953; Arisi et al 1983). Left ventricular structural complexity results in a spatial and temporal inhomogeneity of the chamber wall function (Hotta 1967; Lew and LeWinter 1986; Rademakers et al 1994; Takayama et al 2002). This phenomenon manifests as a difference in regional stresses, shortening, thickening and lengthening (Greenbaum and Gibson 1981; Villarreal and Lew 1990; Balzer et al 1999; Delepine et al 1999; Krahwinkel et al 2000). It is difficult to imagine that the performance of an inhomogeneous muscular pump could be higher than that of a homogeneous one such as a sphere
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