Histological and morphometric changes in cardiac conduction fibers after spontaneous myocardial infarction in horses and dogs

Figures

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  Figure 1. Cardiac conduction fibers of horses and dogs in different locations and regions, stained with Hematoxylin-eosin and Masson’s trichrome after myocardial infarction. (a) Cardiac conduction fibers in horses at the intramyocardial level, in the lateral region at 20× and (b) at the subendocardial level in the anterior region at 20×. (c and d) Cardiac conduction fibers in dogs at the subendocardial level, in the septal region at 10× and 20×. CCF=Cardiac conduction fibers, CM=Cardiomyocytes, CT=Connective tissue.

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  Figure 2. Statistical distribution of cardiac conduction fiber thickness by slice, region, or location in horses and dogs. Cardiac conduction fiber thickness by (a) region and (b) location in horses. Cardiac conduction fiber thickness by (c) slice and (d) region in dogs.

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  Figure 3. Morphology of CCCs in horses, stained with hematoxylin-eosin and Masson’s trichrome after myocardial infarction (a) CCCs in subendocardium, in the septal region at 20× and (b) the posterior region at 40×. (c) CCCs in myocardium, in the lateral region. (d) septal region at 40×. CCC=Cardiac conduction cells, CM=Cardiomyocytes, CT=Connective tissue. The arrows indicate myofibrils at the cell periphery.

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  Figure 4. Morphology of cardiac conduction cells in the subendocardium of dogs in myocardial infarction, stained with (a–c) hematoxylin-eosin and (d) Masson’s trichrome. In the (a) posterior region at 20× and (b) anterior region at 40×. Septal region (c) at 20× and (d) 40×. CCC=Cardiac conduction cells, CM=Cardiomyocytes, CT=Connective tissue.

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  Figure 5. (a and b) CCCs detection using the PAS method in horses and dogs. (a) This method is used to identify intracytoplasmic glycogen in horses with myocardial infarction (MI), in the subendocardium, and in the septal region at 20×. (b) This method has little use in dogs with MI since it reveals negativity in the identification of intracytoplasmic glycogen in the conduction cells. (c and d) CCCs detection by immunohistochemical staining with desmin in horses and dogs. CCCs=Cardiac conduction cells, CM=Cardiomyocytes.

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  Figure 6. Different types of conduction fiber-myocardial junctions in horses and dogs after myocardial infarction, stained with hematoxylin-eosin (a) The arrows indicate a contact through cell bodies (CCB) junction in myocardium, in the septal region at 20× in horses. (b) The arrow reveals contact through cell prolongations (CCP) in myocardium in horses, in anterior region at 20×. (c) Note the contact through transitional cardiomyocytes (CTC) in myocardium in horses, in the anterior region at 20×. (d) Contact through cell bodies (CCB) junction in subendocardium, in anterior region at 40× in dogs. (e) Contact through cell prolongations (CCP) in subendocardium in dogs in the posterior region at 40×. (f) Contact through transitional cardiomyocytes (CTC) in subendocardium in dogsin the lateral region at 40×. CCC=Cardiac conduction cells, CM=Cardiomyocytes, TC=Transitional cells.

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  Figure 7. Area of myocardial infarction in horses and dogs stained with hematoxylin-eosin. (a) Large areas of fibrous scarring were observed in horses, mainly in the posterior region at 4×. (b) In dogs, small areas of fibrosis were recognized, distributed more frequently in the anterior and posterior regions at 20×. Note the lack of continuity of the muscle fibers due to the infarcted area and the presence of some inflammatory cells. FA=Fibrotic area, CM=Cardiomyocytes.