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Glycogen and the propensity for atrial fibrillation: intrinsic anatomic differences in glycogen in the left and right atria in the goat heart.

Embi AA, Scherlag BJ, Ritchey JW - N Am J Med Sci (2014)

Bottom Line: Previous experimental studies have demonstrated electrophysiological and structural remodeling in pacing induced atrial fibrillation.We are reporting for the first time that the right atrial appendage showed scattered glycogen granules throughout the atrial myocytes which delineated the intercalated discs; whereas glycogen in the left atrial appendage was more dense within cells and coalesced against the intercalated discs and side to side junctions between myocytes.We show that glycogen is heterogeneously distributed in both atria in the normal goat heart; however, the density of glycogen deposits concentrating against the intercalated discs and side to side connections in the left atrial appendage is a critically distinct difference.

View Article: PubMed Central - PubMed

Affiliation: Independent, Miami, Florida, USA.

ABSTRACT

Background: Previous experimental studies have demonstrated electrophysiological and structural remodeling in pacing induced atrial fibrillation. The latter has been characterized by glycogen accumulation but no connection to atrial fibrillation induction and maintenance has as yet been proposed.

Aims: We determined the presence of glycogen in the right and left atrial appendages in the goat heart, in order to find any intrinsic disparity in distribution and concentration between these sites.

Materials and methods: Atrial appendages from 5 goats were stained by the Periodic acid Schiffmethod to determine the presence of glycogen and the concentration of glycogen by morphometric analysis.

Results: We are reporting for the first time that the right atrial appendage showed scattered glycogen granules throughout the atrial myocytes which delineated the intercalated discs; whereas glycogen in the left atrial appendage was more dense within cells and coalesced against the intercalated discs and side to side junctions between myocytes. Also, morphometric analysis determined that the stained regions of the right atrial appendages averaged, 0.8 ± 1.3 μm(2) compared to the left atrial appendage sections, 2.6 ± 3 μm(2), P = 0.02. We show that glycogen is heterogeneously distributed in both atria in the normal goat heart; however, the density of glycogen deposits concentrating against the intercalated discs and side to side connections in the left atrial appendage is a critically distinct difference. Impediment of cell to cell conduction could result in a non-uniform wavefront of activation, with areas of slowed conduction, predisposing the left atrium to reentrant based atrial fibrillation.

Conclusion: These findings provide a basis for the well-known greater propensity for atrial fibrillation in the left versus the right atrium.

No MeSH data available.


Related in: MedlinePlus

Heart, goat. In contrast to the RAAs, in the LAAs glycogen often concentrated against intercalated discs (arrows) with dense tails of glycogen extending into the cell along the lateral wall at the myocyte-myocyte junction (solid arrowhead). Periodic-acid Schiff (PAS) stain without diastase treatment. Diastase treatment cleared magenta PAS staining (not shown). Bar = 50 μm
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Figure 2: Heart, goat. In contrast to the RAAs, in the LAAs glycogen often concentrated against intercalated discs (arrows) with dense tails of glycogen extending into the cell along the lateral wall at the myocyte-myocyte junction (solid arrowhead). Periodic-acid Schiff (PAS) stain without diastase treatment. Diastase treatment cleared magenta PAS staining (not shown). Bar = 50 μm

Mentions: Glycogen could be demonstrated in all LAAs and RAAs; however, there was marked variability in the intensity and distribution of glycogen deposition from animal to animal. Glycogen distribution was similar in both formalin-fixed and ethanol-fixed tissue samples. The formalin fixed tissue samples provided for more crisp images for photography and morphometric analysis (because of superiority of formalin for fixation). Glycogen deposition in both RAAs and LAAs was most consistently located in the subepicardial and subendocardial myocardium [Figures 1 and 2 respectively]. Glycogen was also present in the mid-myocardium; however, this was most conspicuous in LAAs (only) and in goats with the highest levels of myocardial glycogen. Although the glycogen content was markedly variable from animal to animal, the LAAs consistently had higher glycogen levels based upon PAS staining.


Glycogen and the propensity for atrial fibrillation: intrinsic anatomic differences in glycogen in the left and right atria in the goat heart.

Embi AA, Scherlag BJ, Ritchey JW - N Am J Med Sci (2014)

Heart, goat. In contrast to the RAAs, in the LAAs glycogen often concentrated against intercalated discs (arrows) with dense tails of glycogen extending into the cell along the lateral wall at the myocyte-myocyte junction (solid arrowhead). Periodic-acid Schiff (PAS) stain without diastase treatment. Diastase treatment cleared magenta PAS staining (not shown). Bar = 50 μm
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4215488&req=5

Figure 2: Heart, goat. In contrast to the RAAs, in the LAAs glycogen often concentrated against intercalated discs (arrows) with dense tails of glycogen extending into the cell along the lateral wall at the myocyte-myocyte junction (solid arrowhead). Periodic-acid Schiff (PAS) stain without diastase treatment. Diastase treatment cleared magenta PAS staining (not shown). Bar = 50 μm
Mentions: Glycogen could be demonstrated in all LAAs and RAAs; however, there was marked variability in the intensity and distribution of glycogen deposition from animal to animal. Glycogen distribution was similar in both formalin-fixed and ethanol-fixed tissue samples. The formalin fixed tissue samples provided for more crisp images for photography and morphometric analysis (because of superiority of formalin for fixation). Glycogen deposition in both RAAs and LAAs was most consistently located in the subepicardial and subendocardial myocardium [Figures 1 and 2 respectively]. Glycogen was also present in the mid-myocardium; however, this was most conspicuous in LAAs (only) and in goats with the highest levels of myocardial glycogen. Although the glycogen content was markedly variable from animal to animal, the LAAs consistently had higher glycogen levels based upon PAS staining.

Bottom Line: Previous experimental studies have demonstrated electrophysiological and structural remodeling in pacing induced atrial fibrillation.We are reporting for the first time that the right atrial appendage showed scattered glycogen granules throughout the atrial myocytes which delineated the intercalated discs; whereas glycogen in the left atrial appendage was more dense within cells and coalesced against the intercalated discs and side to side junctions between myocytes.We show that glycogen is heterogeneously distributed in both atria in the normal goat heart; however, the density of glycogen deposits concentrating against the intercalated discs and side to side connections in the left atrial appendage is a critically distinct difference.

View Article: PubMed Central - PubMed

Affiliation: Independent, Miami, Florida, USA.

ABSTRACT

Background: Previous experimental studies have demonstrated electrophysiological and structural remodeling in pacing induced atrial fibrillation. The latter has been characterized by glycogen accumulation but no connection to atrial fibrillation induction and maintenance has as yet been proposed.

Aims: We determined the presence of glycogen in the right and left atrial appendages in the goat heart, in order to find any intrinsic disparity in distribution and concentration between these sites.

Materials and methods: Atrial appendages from 5 goats were stained by the Periodic acid Schiffmethod to determine the presence of glycogen and the concentration of glycogen by morphometric analysis.

Results: We are reporting for the first time that the right atrial appendage showed scattered glycogen granules throughout the atrial myocytes which delineated the intercalated discs; whereas glycogen in the left atrial appendage was more dense within cells and coalesced against the intercalated discs and side to side junctions between myocytes. Also, morphometric analysis determined that the stained regions of the right atrial appendages averaged, 0.8 ± 1.3 μm(2) compared to the left atrial appendage sections, 2.6 ± 3 μm(2), P = 0.02. We show that glycogen is heterogeneously distributed in both atria in the normal goat heart; however, the density of glycogen deposits concentrating against the intercalated discs and side to side connections in the left atrial appendage is a critically distinct difference. Impediment of cell to cell conduction could result in a non-uniform wavefront of activation, with areas of slowed conduction, predisposing the left atrium to reentrant based atrial fibrillation.

Conclusion: These findings provide a basis for the well-known greater propensity for atrial fibrillation in the left versus the right atrium.

No MeSH data available.


Related in: MedlinePlus