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Fractionation of electrograms is caused by colocalized conduction block and connexin disorganization in the absence of fibrosis as AF becomes persistent in the goat model.

Kirubakaran S, Chowdhury RA, Hall MC, Patel PM, Garratt CJ, Peters NS - Heart Rhythm (2014)

Bottom Line: Electrogram fractionation and atrial fibrosis are both thought to be pathophysiological hallmarks of evolving persistence of atrial fibrillation (AF), but recent studies in humans have shown that they do not colocalize.The interrelationship and relative roles of fractionation and fibrotic change in AF persistence therefore remain unclear.Despite refractoriness returning to normal in between each 4-week period of AF, there was a cumulative increase in the prevalence of fractionated atrial electrograms during both atrial pacing (control and 1, 2, and 3 months period of AF 0.3%, 1.3% ± 1.5%, 10.6% ± 2%, and 17% ± 5%, respectively; analysis of variance, P < .05) and AF (0.3% ± 0.1%, 2.3% ± 1.2%, 14% ± 2%, and 23% ± 3%; P < .05) caused by colocalized areas of conduction block during both pacing (local conduction velocity <10 cm/s: 0.1% ± 0.1%, 0.3% ± 0.6%, 6.5% ± 3%, and 6.9% ± 4%; P < .05) and AF (1.5% ± 0.5%, 2.7% ± 1.1%, 10.1% ± 1.2%, and 13.6% ± 0.4%; P < .05), associated with an increase in the heterogeneity of Cx40 and lateralization of Cx43 (lateralization scores: 1.75 ± 0.89, 1.44 ± 0.31, 2.85 ± 0.96, and 2.94 ± 0.31; P < .02), but not associated with change in connective tissue content or net conduction velocity.

View Article: PubMed Central - PubMed

Affiliation: Manchester Heart Centre, Manchester Royal Infirmary, Manchester, M13 9WL, United Kingdom. Electronic address: senthilk1uk@yahoo.co.uk.

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Tissue fiber orientation is indicated using double-headed dotted arrows. Examples of the Cx43 label in the region of the intercalated disc are shown by vertical arrows, and those of Cx43 along the lateral membrane are shown by horizontal arrows. A: In the image for score 1, the majority of Cx43 immunolabel is confined to the ends of the myocytes in the location of the intercalated disc. B: In the image for score 5, the immunolabel is found along the length of the lateral membrane. Cx43 = connexin 43.
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f0015: Tissue fiber orientation is indicated using double-headed dotted arrows. Examples of the Cx43 label in the region of the intercalated disc are shown by vertical arrows, and those of Cx43 along the lateral membrane are shown by horizontal arrows. A: In the image for score 1, the majority of Cx43 immunolabel is confined to the ends of the myocytes in the location of the intercalated disc. B: In the image for score 5, the immunolabel is found along the length of the lateral membrane. Cx43 = connexin 43.

Mentions: The whole area of the sections on the slide were viewed on an epifluorescence microscope and scored. Where the majority of the tissue showed normally distributed Cx43 (<10% of the sample showing lateralization), a score of 1 was given; a score of 5 was given if more than 40% of the sample showed lateralization (Figure 3; see Online Supplemental Methods).


Fractionation of electrograms is caused by colocalized conduction block and connexin disorganization in the absence of fibrosis as AF becomes persistent in the goat model.

Kirubakaran S, Chowdhury RA, Hall MC, Patel PM, Garratt CJ, Peters NS - Heart Rhythm (2014)

Tissue fiber orientation is indicated using double-headed dotted arrows. Examples of the Cx43 label in the region of the intercalated disc are shown by vertical arrows, and those of Cx43 along the lateral membrane are shown by horizontal arrows. A: In the image for score 1, the majority of Cx43 immunolabel is confined to the ends of the myocytes in the location of the intercalated disc. B: In the image for score 5, the immunolabel is found along the length of the lateral membrane. Cx43 = connexin 43.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4315883&req=5

f0015: Tissue fiber orientation is indicated using double-headed dotted arrows. Examples of the Cx43 label in the region of the intercalated disc are shown by vertical arrows, and those of Cx43 along the lateral membrane are shown by horizontal arrows. A: In the image for score 1, the majority of Cx43 immunolabel is confined to the ends of the myocytes in the location of the intercalated disc. B: In the image for score 5, the immunolabel is found along the length of the lateral membrane. Cx43 = connexin 43.
Mentions: The whole area of the sections on the slide were viewed on an epifluorescence microscope and scored. Where the majority of the tissue showed normally distributed Cx43 (<10% of the sample showing lateralization), a score of 1 was given; a score of 5 was given if more than 40% of the sample showed lateralization (Figure 3; see Online Supplemental Methods).

Bottom Line: Electrogram fractionation and atrial fibrosis are both thought to be pathophysiological hallmarks of evolving persistence of atrial fibrillation (AF), but recent studies in humans have shown that they do not colocalize.The interrelationship and relative roles of fractionation and fibrotic change in AF persistence therefore remain unclear.Despite refractoriness returning to normal in between each 4-week period of AF, there was a cumulative increase in the prevalence of fractionated atrial electrograms during both atrial pacing (control and 1, 2, and 3 months period of AF 0.3%, 1.3% ± 1.5%, 10.6% ± 2%, and 17% ± 5%, respectively; analysis of variance, P < .05) and AF (0.3% ± 0.1%, 2.3% ± 1.2%, 14% ± 2%, and 23% ± 3%; P < .05) caused by colocalized areas of conduction block during both pacing (local conduction velocity <10 cm/s: 0.1% ± 0.1%, 0.3% ± 0.6%, 6.5% ± 3%, and 6.9% ± 4%; P < .05) and AF (1.5% ± 0.5%, 2.7% ± 1.1%, 10.1% ± 1.2%, and 13.6% ± 0.4%; P < .05), associated with an increase in the heterogeneity of Cx40 and lateralization of Cx43 (lateralization scores: 1.75 ± 0.89, 1.44 ± 0.31, 2.85 ± 0.96, and 2.94 ± 0.31; P < .02), but not associated with change in connective tissue content or net conduction velocity.

View Article: PubMed Central - PubMed

Affiliation: Manchester Heart Centre, Manchester Royal Infirmary, Manchester, M13 9WL, United Kingdom. Electronic address: senthilk1uk@yahoo.co.uk.

Show MeSH
Related in: MedlinePlus