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Updated: Sep 21, 2026

In Vitro Assessment of Cardiac Function Using Skinned Cardiomyocytes
Published on: June 22, 2020
Exponential fitting of postextrasystolic potentiation may underestimate the cardiac Ca2+ recirculation fraction: a
Yumiko Doi1, Junichi Araki, Waso Fujinaka
1Department of Anesthesiology and Resuscitology, Okayama University Graduate School of Medicine and Dentistry, 2-5-1 Shikata-cho, Okayama, 700-8558, Japan. yumdoi@yahoo.co.jp
Abstract:
The recirculation fraction of intramyocardial Ca(2+) (RF) has conventionally been obtained from the monotonic decay of postextrasystolic potentiation (PESP). The used assumption is that the decay is exponential. However, we have found that PESP usually decays in alternans even at spontaneous heart rates (>100 beats/min) in excised, cross-circulated canine heart preparations under normal coronary perfusion and normothermia. We have already devised a means of extracting the exponential decay component for RF calculation by subtracting the oscillatory component from the alternans PESP decay by a curve-fitting method. Using mathematics, we assessed the possible error in estimated RF when an exponential curve was naively fit to the alternans PESP decay. We obtained results showing that the exponential assumption may considerably underestimate RF even when the alternans is trivial with the oscillatory component of only 10% of the exponential component.
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