Biomedical subjects

Natalia Trayanova

Publications and source records attributed to Natalia Trayanova.

21 records · Page 2Linked to original sources

PubMed2002

Shock-induced arrhythmogenesis in the myocardium.

The focus of this article is the investigation of the electrical behavior of the normal myocardium following the delivery of high-strength defibrillation shocks. To achieve its goal, the study employs a complex three-dimensional defibrillation model of a slice of the canine heart characterized with realistic geometry and fiber architecture. Defibrillation shocks of various strengths and electrode configurations are delivered to the model preparation in which a sustained ventricular tachycardia is induced. Instead of analyzing the post-shock electrical events as progressions of transmembrane potential maps, the study examines the evolution of the postshock phase singularities (PSs) which represent the organizing centers of reentry. The simulation results demonstrate that the shock induces numerous PSs the majority of which vanish before the reentrant wavefronts associated with them complete half of a single rotation. Failed shocks are characterized with one or more PSs that survive the initial period of PS annihilation to establish a new postshock arrhythmia. The increase in shock strength results in an overall decrease of the number of PSs that survive over 200 ms after the end of the shock; however, the exact behavior of the PSs is strongly dependent on the shock electrode configuration. (c) 2002 American Institute of Physics.

Journal Article↗

PubMed1998

The role of cardiac tissue structure in defibrillation.

The purpose of this paper is to investigate the relationship between cardiac tissue structure, applied electric field, and the transmembrane potential induced in the process of defibrillation. It outlines a general understanding of the structural mechanisms that contribute to the outcome of a defibrillation shock. Electric shocks defibrillate by changing the transmembrane potential throughout the myocardium. In this process first and foremost the shock current must access the bulk of myocardial mass. The exogenous current traverses the myocardium along convoluted intracellular and extracellular pathways channeled by the tissue structure. Since individual fibers follow curved pathways in the heart, and the fiber direction rotates across the ventricular wall, the applied current perpetually engages in redistribution between the intra- and extracellular domains. This redistribution results in changes in transmembrane potential (membrane polarization): regions of membrane hyper- and depolarization of extent larger than a single cell are induced in the myocardium by the defibrillation shock. Tissue inhomogeneities also contribute to local membrane polarization in the myocardium which is superimposed over the large-scale polarization associated with the fibrous organization of the myocardium. The paper presents simulation results that illustrate various mechanisms by which cardiac tissue structure assists the changes in transmembrane potential throughout the myocardium. (c) 1998 American Institute of Physics.

Journal Article↗

PubMedDate not supplied

Analysis of electrically induced reentrant circuits in a sheet of myocardium.

Understanding the complex spatiotemporal dynamics of action potential propagation in the heart during arrhythmia is exceedingly difficult. This study applies nonlinear dynamics tools to simplify this task. Using the results of a simulation of an electrical induction of reentry in a sheet of myocardium represented as a bidomain, transmembrane voltage maps are processed to obtain: (i) spatial maps of phase angle and phase singularity trajectories, (ii) state scatter plots, and (iii) spatial maps of even phase resetting, wave fronts and wave tails. Tracking the phase singularities allows us to identify the "seeds" of reentry before the reentrant circuit is formed and to characterize the spatiotemporal evolution of the organizing center of the reentrant circuit. The state scatter plots demonstrate the effect of the shock on the instantaneous state of the system. The spatial maps of even phase resetting allow us to identify the shock-induced excitable gaps (regions of regenerative repolarization) as well as the regions directly activated by the shock. These nontraditional approaches to the analysis of electrophysiological phenomena greatly enhance our ability to conceptualize the dynamics of arrhythmias.

Action Potentials↗