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Altered T wave dynamics in a contracting cardiac model

N. P. Smith‚ M. L. Buist and A. J. Pullan

Abstract

INTRODUCTION: The implications of mechanical deformation on calculated body surface potentials are investigated using a coupled biophysically based model. METHODS AND RESULTS: A cellular model of cardiac excitation-contraction is embedded in an anatomically accurate two-dimensional transverse cross-section of the cardiac ventricles and human torso. Waves of activation and contraction are induced by the application of physiologically realistic boundary conditions and solving the bidomain and finite deformation equations. Body surface potentials are calculated from these activation profiles by solving Laplace's equation in the passive surrounding tissues. The effect of cardiac deformation on electrical activity, induced by contraction, is demonstrated in both single-cell and tissue models. Action potential duration is reduced by 7 msec when the single cell model is subjected to a 10% contraction ramp applied over 400 msec. In the coupled electromechanical tissue model, the T wave of the ECG is shown to occur 18 msec earlier compared to an uncoupled excitation model. To assess the relative effects of myocardial deformation on the ECG, the activation sequence and tissue deformation are separated. The coupled and uncoupled activation sequences are mapped onto the undeforming and deforming meshes, respectively. ECGs are calculated for both mappings. CONCLUSION: Adding mechanical contraction to a mathematical model of the heart has been shown to shift the T wave on the ECG to the left. Although deformation of the myocardium resulting from contraction reduces the T wave amplitude, cell stretch producing altered cell membrane kinetics is the major component of this temporal shift.

Journal
J Cardiovasc Electrophysiol
Keywords
Action Potentials/physiology Algorithms Animals Anisotropy Calcium/physiology Cell Membrane/physiology Dogs *Electrocardiography Electrophysiology Heart/*physiology Humans Kinetics Membrane Potentials/physiology Models‚ Biological Models‚ Statistical Myocardial Contraction/*physiology Myocardium/metabolism Troponin C/physiology
Note
Journal Article Research Support‚ Non−U.S. Gov't United States
Number
10 Suppl
Pages
S203−9
Volume
14
Year
2003