Cardiac pathology findings in 252 cats presented for necropsy; a comparison of cats with unexpected death versus other deaths.

Objectives: To report necropsy and myocardial histopathology in cats with unexpected death and expected death/euthanasia, comparing findings in 4 groups of cats: unexpected death with noncardiac disease (UD-NC); unexpected death with cardiac disease (UD-C); expected death/euthanasia due to noncardiac disease with incidental cardiac disease (OD + HD); and expected death/euthanasia due to congestive heart failure (CHF).

Animals: Two hundred fifty-two cats undergoing necropsy at a single centre.

Methods: Signalment, history, body weight, heart weight and myocardial thickness were obtained from medical records. Cardiac histopathology slides were reviewed blindly by a single observer. Data were analysed using a Chi squared, Fisher's exact, Kruskal-Wallis tests or ANOVA as appropriate.

Results: Death at a veterinary clinic and suspected poisoning were the most common reasons for necropsy in 158 cats with an unexpected death. No cause other than cardiac disease was found in 87/158 (55.1%), with hypertrophic cardiomyopathy identified in 68/87 (78%) of UD-C cats. Expected deaths or euthanasia occurred in 27 cats with CHF and 67 cats with concurrent heart disease (OD + HD). Myofiber disarray, interstitial fibrosis, subendocardial fibrosis and intramural arteriolosclerosis were more prevalent in UD-C cats than in UD-NC cats, and subendocardial fibrosis and arteriolosclerosis were more prevalent in UD-C cats than in CHF and OD + HD cats.

Conclusions: Cardiac disease, and hypertrophic cardiomyopathy in particular, was commonly present in cats that died unexpectedly in this study population. Subendocardial fibrosis and intramural arteriolosclerosis were more common in cats with unexpected death with cardiac disease than in other cats.