A simulation study of the effects of torso inhomogeneities on electrocardiographic potentials, using realistic heart and torso models.

Abstract

SUMMARY. The effects of torso inhomogeneities on electrocardiographic potentials were investigated via computer simulation, using a 23-dipole heart model placed within a realistically shaped human torso model. The transfer coefficients relating the individual dipoles to the torso surface potentials, as well as the body surface potential maps, the vectorcardiogram, and the 12-lead electrocardiogram resulting due to normal activation of the heart model, were calculated for each of the following torso conditions: homogeneous, homogeneous + skeletal muscle layer, homogeneous + muscle layer + lungs, and homogeneous + muscle layer + lungs + intraventricular blood masses. The effects of each inhomogeneity were deduced by comparing results before and after its inclusion. For individual dipole transfer coefficients we confirm the validity of the "Brody effect," whereby the high conductivity blood masses augment radially oriented dipoles and diminish tangentially oriented ones. With regard to the vectorcardiogram, the electrocardiogram, and the body surface potential maps, the major qualitative effects were an augmentation of the head-to-foot component of the vectorcardiogram due to the lungs, and a smoothening of notches in the electrocardiogram (temporal filtering) and of isopotential contours in the body surface potential maps (spatial filtering) with a consequent loss of information, due to the blood masses, muscle layer, and, to a lesser extent, the lungs. Besides the above qualitative effects of the inhomogeneities, there were also large quantitative effects on the surface potentials, namely, magnitude increases due to the blood masses and magnitude decreases due to the muscle layer, that-if unaccounted for-could compromise the inverse solution of these potentials for the cardiac dipole sources. (Ore Res 52: 45-56, 1983)

Mathematical Modeling and Simulation of Ventricular Activation Sequences: Implications for Cardiac Resynchronization Therapy

“…A similar model was used by Gulrajani and Mailloux to quantify the effect of the lungs and intracavitary blood masses on the ECG [35]. …”

Noninvasive Imaging of Cardiac Electrophysiology (NICE)

“…The volume conductor model is a representation of the patient individual geometry comprising the electrically most relevant compartments, which distinguish themselves by their different electrical properties, such as the electrical conductivity (Geselowitz D. B., 1967;Gulrajani R. M. & Mailloux G. E., 1983;Klepfer R. N. et al, 1997;Malmivuo J. & Plonsey R., 1995;Pullan A. J. et al, 2001): heart, bloodmasses within the heart's cavities, left and right lung, and torso.…”

Multipole Approach to the Inverse Problem in Electrocardiology: Convergence of the Multipole Equivalent Generator on the Inhomogeneous Body Conductor

“…We take this additional inhomogeneity into account, because the layer is close to the heart current sources; it obviously plays a role in the multipole convergence criterion, and, probably, it affects the rate of convergence of the multipole generator. The anisotropic conductivity properties of the muscle layer are taken into account by dilating the layer with a factor 1.94 (McFee and Rush, 1968;Cornelis, 1980;Gulrajani and Mailloux, 1983). This has two consequences: (1) the muscle layer is now considered to have an isotropic conductivity of 0.155…”

“…The operation performed here is different from Gulrajani and Mailloux (1983) in two ways. First, whereas in Gulrajani and Mailloux (1983) the thickness of the layer is constant (1 cm), we use a variable thickness between 0.8 and 3 cm. The thickness values are derived on the basis of anatomical observations (e.g., the layer is much thicker at the back of the torso than at the front).…”

“…This results in different values for the isotropic conductivity and for the dilation factor [in Gulrajani and Mailloux (1983) For the cardiac current sources the uniform double-layer model is used. The model data comprises the geometry of the endocardial and epicardial surfaces and the distribution of the depolarization times on these surfaces.…”