Etiology:  There are several factors thought to predispose rats to this condition including chronic myocarditis or myocardial ischemia.  Age and the concomitant development of chronic progressive nephropathy may also contribute.

Incidence:  Incidence is common, especially in SD rats.  Older males are more commonly affected.

Clinical Signs:  Usually there are no clinical signs.

Pathology:  Grossly, there may be multifocal grey lesions in the left ventricle.  Histologically, there is myocardial atrophy, necrosis and collagen deposition (fibrosis) with interstitial infiltration with mononuclear cells [3].

Diagnosis:  Diagnosis is made based on histopathologic findings.

3.            The Laboratory Rat, ed. M.A. Suckow, Weisbroth, Steven H., Franklin, Craig L.2006, 30 Corporate Drive, Suite 400, Burlington, MA 01803 Elsevier.