Abstract
Background:
In humans and cats hypertrophic cardiomyopathy (HCM) is a cause of sudden cardiac death. This is usually associated with arrhythmias, based on myocardial fibrosis and electric impulse propagation disturbances. Restrictive cardiomyopathy (RCM) is a cardiomyopathy associated with excessive fibrosis which is predisposed to arrhythmic episodes. Electric coupling in the myocardium is based on His-Purkinje system and cardiomyocytes cell-to-cell contacts. Cell connection is based on gap junctions and their structural proteins - connexins. Today there is a lack of information in literature regarding these functional units and their distribution in cats.

Aim:
Discover presence of connexin43 (Cx43) in myocardial tissues of cats and differentiate in HCM and RCM phenotypes

Methods:
Retrospective analysis of materials collected from cats with cardiomyopathy.

Results:
Animals with histological and immunohistochemical markers of HCM and RCM. Cx 43 was distributed in myocardial tissue of a heathy cat in a typical pattern to other described animals (rats, mice, human). In HCM, Cx43 was decreased and lateralized near fibrotic zones and was absent in the scar tissue. In RCM, there was a similar pattern but there were also loci with spontaneously altered expression of Cx43, forming lacunas in the gap junction or presented as an intermittent granulated mass.

Conclusion:
Cx43 has different patterns of expression in different cardiomyopathies phenotypes, however, role of this fact in arrhythmogenesis needs to be studied.

Key words: Feline, Myocardium, Hypertrophic cardiomyopathy, Restrictive cardiomyopathy, Connexin 43