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Life Sci. 2016 Jan 1;144:170-7. doi: 10.1016/j.lfs.2015.12.019. Epub 2015 Dec 8.

Effects of central sympathetic activation on repolarization-dispersion during short-term myocardial ischemia in anesthetized rats.

Author information

1
Cardiovascular Research Institute, Ioannina and Athens, Greece. Electronic address: theofilos.m.kolettis@gmail.com.
2
Cardiovascular Research Institute, Ioannina and Athens, Greece.
3
Experimental Research Center ELPEN, Pikermi, Athens, Greece.
4
Cardiovascular Research Institute, Ioannina and Athens, Greece; Experimental Research Center ELPEN, Pikermi, Athens, Greece.

Abstract

AIMS:

Sympathetic activation during myocardial ischemia enhances arrhythmogenesis, but the underlying pathophysiologic mechanisms remain unclear. We investigated the central sympathetic effects on ventricular repolarization during the early-period post-coronary artery occlusion.

MAIN METHODS:

We studied 12 Wistar rats (254±2 g) for 30 min following left coronary artery ligation, with (n=6) or without (n=6) pretreatment with the central sympatholytic agent clonidine. Mapping of left and right ventricular epicardial electrograms was performed with a 32-electrode array. As an index of sympathetic activation, heart rate variability in the frequency domain was calculated. Heart rate and repolarization duration were measured with a custom-made recording and analysis software, followed by calculation of intra- and inter-ventricular dispersion of repolarization.

KEY FINDINGS:

Heart rate and heart rate variability indicated lower sympathetic activation in clonidine-treated rats during ischemia. Repolarization duration in the left ventricle prolonged after clonidine at baseline, independently of heart rate, but no differences were present 30 min post-ligation. Dispersion of repolarization in the right ventricle remained stable during ischemia, whereas it increased in the left ventricle, equally in both groups. A similar trend was observed for inter-ventricular dispersion, without differences between groups.

SIGNIFICANCE:

In addition to intra-ventricular repolarization-dispersion, anterior-wall myocardial ischemia may also increase inter-ventricular repolarization-dispersion. Progressive central sympathetic activation occurs during myocardial ischemia, but it does not affect intra- or inter-ventricular dispersion of ventricular repolarization during the early phase. Further research is warranted on the potential effects during subsequent time-periods.

KEYWORDS:

Central sympathetic activation; Myocardial ischemia; Repolarization-dispersion; Ventricular repolarization

PMID:
26679103
DOI:
10.1016/j.lfs.2015.12.019
[Indexed for MEDLINE]

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