Findings suggestive of coronary microvascular dysfunction in cats with myocardial ischemia

BACKGROUND: Myocardial infarction (MI) is an important cause of death and disability among humans worldwide. Few studies have reported the occurrence of MI in small animals as well. 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 (CMD). AIM: This study aimed to describe the necropsy findings and clinical-pathological characterization (when available) of cats with histopathological findings suggesting CMD. METHODS: Necropsy records of cats presenting histopathological diagnosis compatible with acute and/or chronic MI, 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 (HCM) without left atrial enlargement, one (5%) presented restrictive cardiomyopathy, and another one (5%) had lesions consistent with histiocytoid cardiomyopathy. The remaining cats (50%) showed alterations compatible with severe HCM 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: These findings suggest the presence of microvascular dysplasia of the coronary arteries. Further studies are necessary to confirm and clinically characterize these results.