Reference Values for Postmortem Examination of the Heart in the Macropod (Macropodidae) and Koala (Phascolarctidae).

Morphometric cardiac reference values are reported for macropods and koalas (Phascolarctos cinereus). Body weight (BW), heart weight (HW), left ventricle (LV) wall, interventricular septum (S), right ventricle (RV) wall thickness, and LV+S and RV weights were measured at postmortem examination of 48 macropods and 32 koalas that had no evidence of cardiovascular disease. The HW/BW% (0.43-0.96%) and (LV+S)/RV (2.80-4.22) for macropods were comparable to domestic species. In koalas, the HW/BW% (0.25-0.51%) was lower, and the (LV+S)/RV (3.06-5.41) ranged higher than in macropods and domestic species. The LV:RV of koalas (1.0-10.8) was more variable than in macropods (1.17-4.27). Two macropods with cardiac disease were assessed on postmortem examination against the generated reference values. An adult male common wallaroo (Osphranter robustus) was found dead with copious serous peritoneal effusion, chronic passive hepatic congestion with centrilobular fibrosis, and dilation of the RV, while the LV:RV was elevated, supportive of RV thinning. A 21-year-old female zoo-housed Matschie's tree kangaroo (Dendrolagus matschiei) had a flaccid thin-walled RV, LV cardiomyocyte hypertrophy, interstitial myocardial fibrosis and myofiber degeneration, pulmonary oedema, and serous pericardial effusion. The (LV+S)/RV and LV:RV were elevated and RV:S decreased, supporting left hypertrophic cardiomyopathy. Species-specific reference values presented in this study facilitate objective and improved postmortem cardiac assessment in macropods and koalas.