Abstract

Abstract
Background
Myocardial infarction is an important cause of death and disability in humans worldwide. Few studies have reported the occurrence of myocardial infarction in small animals. Reports in human medicine indicate that up to 30% of patients with clinical signs compatible with myocardial ischemia suggestive of coronary disease exhibit normal epicardial arteries at angiography. These symptoms have been associated with a syndrome characterized by alterations in cardiac microvasculature, known as coronary microvascular dysfunction.
Aim
The aim of this study was to describe the necropsy findings along with clinical-pathological characterization (when available) of cats with histopathological findings suggesting coronary microvascular dysfunction.
Methods
Necropsy records of cats presenting histopathological diagnosis compatible with acute and/or chronic myocardial infarction, with normal epicardial arteries and microvascular disorders were evaluated.
Results
Twenty animals met the inclusion criteria. Eight cats (40%) exhibited findings compatible with mild hypertrophic cardiomyopathy without left atrial enlargement, one (5 %) presented restrictive cardiomyopathy and another one (5 %) had findings compatible with histiocytoid cardiomyopathy (5%). The remaining cats (50 %) showed alterations compatible with severe hypertrophic cardiomyopathy with left atrial enlargement. In all cases, epicardial arteries were normal (without obstruction). All the evaluated hearts exhibited myocardial multifocal fibrosis along with replacement of cardiomyocytes by adipose tissue and blood vessels with hyperplasia and hypertrophy of the muscular layer with protrusion of the nuclei of the endothelial cells.
Conclusion
Those findings suggest the presence of microvascular dysplasia of the coronary arteries. Further studies are necessary to confirm and clinically characterize these results.

Key words: Coronary microcirculation, microvascular dysfunction, feline ischemia