Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
874693 | Journal of Biomechanics | 2006 | 8 Pages |
Abstract
In order to determine the mode of beat-to-beat decay of contractility from very high levels, we studied the beat-by-beat decay of cardiac contractility following potentiation. Such decay curves are normally analysed using a mono-exponential decay function, which assumes that a fixed fraction of activator calcium ions is recirculated from one beat to the next. We postulated that there might be deviations from such a mono-exponential expression at high levels of contractility. In single sucrose-gap voltage clamp experiments of isolated ferret papillary muscle, we obtained very high contractility by potentiation due to prolonged depolarisations. We found a bi-exponential decay in 9 of 11 muscles studied, in which the initial decay is much faster than the subsequent slower decay, as judged by residual variance of least-squares exponential fitting and by analysis of covariance using a linear equation (force of beat versus force of previous beat), p=0.0089. In the slower decay period (physiological range), the decay was identical to that following post-extrasystolic potentiation in the same muscles studied with conventional stimulation.
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Biomedical Engineering
Authors
Mark I.M. Noble, Per Arlock, Bjorn Wohlfart, Angela J. Drake-Holland,