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Type: Artigo de periódico
Title: Combining Stimulus Direction And Waveform For Optimization Of Threshold Stimulation Of Isolated Ventricular Myocytes.
Author: Bassani, Rosana A
Lima, Katherine A
Gomes, Paulo A P
Oliveira, Pedro X
Bassani, José W M
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,L)) rather than transversally (E(T,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 (DeltaV(T) approximately 15 mV) was insensitive to field direction. As DeltaV(T) values were similar, we assumed that the E(T,T)/E(T,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 DeltaV(T), which were greater for monophasic versus biphasic stimuli. Direction and waveform effects were independent. We conclude that (a) direction affects E(T) 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: Action Potentials
Cells, Cultured
Computer Simulation
Differential Threshold
Electric Stimulation
Heart Ventricles
Membrane Potentials
Models, Cardiovascular
Myocytes, Cardiac
Rats, Wistar
Ventricular Function
Citation: Physiological Measurement. v. 27, n. 9, p. 851-63, 2006-Sep.
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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