Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/79067
Type: Artigo de periódico
Title: Combining stimulus direction and waveform for optimization of threshold stimulation of isolated ventricular myocytes
Author: Bassani, RA
Lima, KA
Gomes, PAP
Oliveira, PX
Bassani, JWM
Abstract: Electric field stimulation is widely used for heart pacing and arrhythmia reversion. In this study, we analysed the influence of waveform and direction of external stimulating electric field on the excitation threshold of isolated ventricular myocytes. The threshold field (E-T) was lower when the field was applied longitudinally (E-T,E-L) rather than transversally (E-T,E-T) to the cell major axis. Rheobase was greater for transversal stimulation, but chronaxie and estimated membrane polarization were similar for both directions. The calculated maximal variation in membrane potential at the threshold (Delta V-T similar to 15 mV) was insensitive to field direction. As Delta V-T values were similar, we assumed that the E-T,E-T/E-T,E-L ratio might be described solely as the ratio of the major and minor cell semi-axes. Accordingly, the ratio thus estimated was comparable to that determined experimentally. Stimulus waveform significantly affected both E-T and similar to V-T, which were greater for monophasic versus biphasic stimuli. Direction and waveform effects were independent. We conclude that (a) direction affects ET by its influence on the ability of a given field intensity to cause threshold membrane polarization and (b) threshold-lowering effects of longitudinal stimulation and biphasic waveforms apparently depend on different mechanisms, are additive and thus may be combined to decrease the energy requirement for myocardial stimulation.
Subject: defibrillation
biphasic stimulus
depolarization
intensity-duration relationship
Country: Inglaterra
Editor: Iop Publishing Ltd
Rights: fechado
Identifier DOI: 10.1088/0967-3334/27/9/008
Date Issue: 2006
Appears in Collections:Unicamp - Artigos e Outros Documentos

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