Abstract
The epicardial and endocardial surfaces of the heart are attractive targets to administer antiarrhythmic electrotherapies. Electrically stimulating wide areas of the surfaces of small mammalian ventricles is straightforward given the relatively small scale of their myocardial dimensions compared to the tissue space constant and electrical field. However, it has yet to be proven for larger mammalian hearts with tissue properties and ventricular dimensions closer to humans. Our goal was to address the feasibility and impact of wide-area electrical stimulation on the ventricular surfaces of large mammalian hearts at different stimulus strengths. This was accomplished by placing long line electrodes on the ventricular surfaces of pig hearts that span wide areas, and activating them individually. Stimulus efficacy was assessed and compared between surfaces, and tissue viability was evaluated. Activation time was dependent on stimulation strength and location, achieving uniform linear stimulation at 9x threshold strength. Endocardial stimulation activated more tissue transmurally than epicardial stimulation, which could be considered a potential target for future cardiac electrotherapies. Overall, our results indicate that electrically stimulating wide areas of the ventricular surfaces of large mammals is achievable with line electrodes, minimal tissue damage, and energies under the human pain threshold (100 mJ).
Highlights
The epicardial and endocardial surfaces of the heart are attractive targets to administer antiarrhythmic electrotherapies
A systematic assessment of electrical stimulation strength, electrode positioning, and spacing is lacking to attain uniform stimulation across a wide-area spanning electrode. It is not clear how stimulus efficacy is influenced by the stimulus location according to the cardiac surfaces, and whether these stimulus strengths pose a risk to the tissue viability
We have demonstrated the ability to electrically stimulate wide areas of the epicardial and endocardial surfaces of large mammalian ventricles using line electrodes
Summary
The epicardial and endocardial surfaces of the heart are attractive targets to administer antiarrhythmic electrotherapies. Our goal was to address the feasibility and impact of wide-area electrical stimulation on the ventricular surfaces of large mammalian hearts at different stimulus strengths. A systematic assessment of electrical stimulation strength, electrode positioning, and spacing is lacking to attain uniform stimulation across a wide-area spanning electrode It is not clear how stimulus efficacy is influenced by the stimulus location according to the cardiac surfaces (epicardium versus endocardium), and whether these stimulus strengths pose a risk to the tissue viability. The main objective of this study was to address the feasibility and impact of wide-area electrical stimulation on the ventricular surfaces of large mammalian hearts This investigation sought to determine the following: (1) novel parameters for quantifying uniform stimulation around electrodes spanning wide areas of the heart, especially early activation parameters. Uniform stimulation across the line is of particular importance since it could potentially reduce the risk of forming new wave fronts that could initiate (or reinitiate) an arrhythmia[4]; (2) how these parameters change with respect to stimulus strength and the surface stimulated (endocardium versus epicardium); and (3) the safety of stimulus strength with respect to tissue and cellular viability
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