An Assessment of Variable Thickness and Fiber Orientation of the Skeletal Muscle Layer on Electrocardiographic Calculations

Academic Article

Abstract

  • This paper assesses the effectiveness of including variable thickness and fiber orientation characteristics of the skeletal muscle layer in calculations relating epicardial and torso potentials. A realistic model of a canine torso which includes extensive detail about skeletal muscle layer thickness and fiber orientation is compared with two other uniformly anisotropic models: one of constant thickness and the other of variable thickness. First, transfer coefficients are calculated from the model data. Then torso potentials for each model are calculated from the transfer coefficients and measured epicardial potentials. The comparison of calculated and observed torso potentials indicates that a simple model consisting of a uniformly anisotropic skeletal muscle layer of 1.0–1.5 cm constant thickness significantly improves the model. However, if photographic slices of the canine torso are used to introduce more detailed data about the variation in skeletal muscle thickness and fiber orientation into the model, the agreement and between calculated and measured torso potentials decreased, although a finite element mesh of over 5000 nodes was used to describe the skeletal muscle in the more detailed model. One source of error increase was considered to be due to numerical discretization and could be reduced with a much finer mesh or by utilizing higher order polynomials to represent the potential distribution within each finite element. However, the results presented in this paper show that high precision computation (64-bit word length) on the mainframe IBM 3081 with an attached FPS-164 gives a slow rate of improvement with reduced discretization intervals and that utilizing higher order polynomials within each finite element gives an even slower rate of improvement. The other major source of the error increase is the limited specificity, in this case approximately 45°, with which muscle fiber orientation can be assigned from photographic slices. Thus, the calculations suggest that identifying preferred fiber directions in the muscle layer in the plane tangential to the torso surface with a specificity of 45° may introduce large errors and that a realistic skeletal muscle layer should not be included unless these orientations are accurately known. © 1991 IEEE
  • Authors

    Digital Object Identifier (doi)

    Author List

  • Stanley PC; Pilkington TC; Morrow MN; Ideker RE
  • Start Page

  • 1069
  • End Page

  • 1076
  • Volume

  • 38
  • Issue

  • 11