Feline endomyocarditis and left ventricular endocardial fibrosis.

A retrospective study was conducted of all feline necropsies over a 7-year period. Of a total of 1,472 necropsies, 37 cases of endomyocarditis (EMC) and 25 cases of left ventricular endocardial fibrosis (LVEF) (previously called restrictive or intermediate cardiomyopathy) were identified. There was a subset of four cats with EMC that had histologic features of both diseases. Interstitial pneumonia was seen in 25 of 35 cats (71%) with EMC but in only seven of 25 cats (28%) with LVEF. Thrombi or thromboemboli were seen in 14 of 25 cats (56%) with LVEF but in only six of 37 of cats (16%) with EMC. In both LVEF and EMC, thromboemboli were located in the abdominal aorta, left atrium and ventricle of the heart, femoral artery, cranial mesenteric artery, liver, pulmonary artery, jugular vein, or a meningeal vessel. Each cat had a single thrombus/thromboembolus, except for four cats with LVEF that had more than one. The histologic and clinical findings suggest that EMC and LVEF represent temporally different manifestations of a single disease entity.