NDLI: Effect of rapid delayed rectifier current on hysteresis in restitution of action potential duration in swine

Content Provider	IEEE Xplore Digital Library
Author	Agarwal, A. Linyuan Jing Patwardhan, A.
Copyright Year	2012
Description	Author affiliation: Center for Biomed. Eng., Univ. of Kentucky, Lexington, KY, USA (Patwardhan, A.) \|\| Univ. of Kentucky, Lexington, KY, USA (Agarwal, A.; Linyuan Jing)
Abstract	Electrical stability in the heart depends on two important factors; restitution of action potential duration (APD) and memory. Repolarization currents play an important role in determining APD and also affect memory. We determined the effects of blocking the rapid component of the delayed rectifier $(I_{Kr})$ on a quantifiable measure of memory, i.e. hysteresis in restitution of APD, in swine. Transmembrane potentials were recorded from right ventricular endocardial tissues. Two pacing protocols with explicit control of diastolic interval (DI) were used to change DIs in a sequential and sinusoidal pattern to quantify hysteresis in restitution of APD. E-4031 (5 μM/L) was used to block $I_{Kr}.$ Measures of memory and restitution were quantified by calculating hysteresis loop thickness, area, overall tilt, and maximum and minimum delays between DIs and APDs. Blocking $I_{Kr}$ with E-4031 increased the baseline APD, loop thickness, area, and tilt (p<;0.05). However, loop thickness did not increase beyond what could be predicted by the increase in baseline APD after block of $I_{Kr}.$ The substantial change in APD after blocking $I_{Kr}$ suggests that this current plays a major role in repolarization in the swine. Loop thickness is a measure of memory, an increase in which is predicted by theory to reduce instability in activation. In our study, the substantial increase in loop thickness could be accounted for by an equally substantial increase in APD and therefore does not necessarily indicate increased memory after blocking $I_{Kr}.$ Our results also suggest that factors based on restitution and memory need to be considered in the context of operating point, i.e. baseline APD, when they are used to explore mechanisms that affect electrical stability in the heart.
Sponsorship	IEEE Eng. Medicine Biol. Soc.
Starting Page	673
Ending Page	676
File Size	630938
Page Count	4
File Format	PDF
ISBN	9781424441198
ISSN	1557170X
e-ISBN	9781457717871
DOI	10.1109/EMBC.2012.6346021
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2012-08-28
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Protocols Hysteresis Delay Heart Drugs Current measurement Electric potential
Content Type	Text
Resource Type	Article
Subject	Signal Processing Biomedical Engineering Health Informatics Computer Vision and Pattern Recognition

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