Myocardial mechanical restitution and potentiation partly underlie alternans decay of postextrasystolic potentiation: Simulation |
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Authors: | Satoshi Mohri Junichi Araki Takeshi Imaoka Gentaro Iribe Masaki Maesako Juichiro Shimizu Hiromi Matsubara Tohru Ohe Masahisa Hirakawa Hiroyuki Suga |
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Institution: | (1) Department of Physiology II, Okayama University Medical School, 700-8558 Shikata-cho, Okayama, Japan;(2) Department of Cardiovascular Medicine, Okayama University Medical School, Shikata-cho, 700-8558 Okayama, Japan;(3) Department of Anesthesiology and Resuscitology, Okayama University Medical School, Shikata-cho, 700-8558 Okayama, Japan |
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Abstract: | Summary We have reported that the postextrasystolic potentiation (PESP) decays in alternans or monotonically, respectively, depending
on whether the first postextrasystolic beat interval has a compensatory pause or not, in the canine left ventricle. To get
better mechanistic insight into the alternans PESP decay, we hypothesized that the myocardial mechanical restitution and potentiation
could partly account for both types of PESP decay. To test this hypothesis, we simulated PESP decay on a computer using a
documented equation combining myocardial mechanical restitution and potentiation. We changed the first postextrasystolic beat
interval after a fixed extrasystolic beat interval without changing regular and other postextrasystolic beat intervals. The
simulated PESP decayed in alternans or monotonically as a function only of the first postextrasystolic beat interval. Thus,
the myocardial mechanical restitution and potentiation could partly account for both alternans and monotonic decay of PESP.
We conclude that myocardial mechanical restitution and potentiation may partly underlie the initial two alternating beats,
the first beat being the most potentiated and the second beat being the most depressed, of alternans PESP decay in the canine
heart.
This study was partly supported by Grants-in-Aid for Scientific Research (07508003, 09470009, 10558136, 10770307, 10877006)
from the Ministry of Education, Science, Sports and Culture, and 1997–1998 Frontier Research Grants for Cardiovascular System
Dynamics from the Science and Technology Agency, all of Japan. |
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Keywords: | Force— interval relation Sarcoplasmic reticulum Calcium Extrasystole Compensatory pause |
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