Contrasting effects of ischemia on the kinetics of membrane voltage and intracellular calcium transient underlie electrical alternans

Author:

Lakireddy Vikram,Baweja Paramdeep,Syed Asma,Bub Gil,Boutjdir Mohamed,El-Sherif Nabil

Abstract

Repolarization alternans has been considered a strong marker of electrical instability. The objective of this study was to investigate the hypothesis that ischemia-induced contrasting effects on the kinetics of membrane voltage and intracellular calcium transient (CaiT) can explain the vulnerability of the ischemic heart to repolarization alternans. Ischemia-induced changes in action potential (AP) and CaiT resulting in alternans were investigated in perfused Langendorff guinea pig hearts subjected to 10–15 min of global no-flow ischemia followed by 10–15 min of reperfusion. The heart was stained with 100 μl of rhod-2 AM and 25 μl of RH-237, and AP and CaiT were simultaneously recorded with an optical mapping system of two 16 × 16 photodiode arrays. Ischemia was associated with shortening of AP duration (D) but delayed upstroke, broadening of peak, and slowed decay of CaiT resulting in a significant increase of CaiT-D. The changes in APD were spatially heterogeneous in contrast to a more spatially homogeneous lengthening of CaiT-D. CaiT alternans could be consistently induced with the introduction of a shorter cycle when the upstroke of the AP occurred before complete relaxation of the previous CaiT and generated a reduced CaiT. However, alternans of CaiT was not necessarily associated with alternans of APD, and this was correlated with the degree of spatially heterogeneous shortening of APD. Sites with less shortening of APD developed alternans of both CaiT and APD, whereas sites with greater shortening of APD could develop a similar degree of CaiT alternans but slight or no APD alternans. This resulted in significant spatial dispersion of APD. The study shows that the contrasting effects of ischemia on the duration of AP and CaiT and, in particular, on their spatial distribution explain the vulnerability of ischemic heart to alternans and the increased dispersion of repolarization during alternans.

Publisher

American Physiological Society

Subject

Physiology (medical),Cardiology and Cardiovascular Medicine,Physiology

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3