Double inlet left ventricle in a 12-year-old European bison: a case report with anatomical assessment and postmortem computed tomography evaluation

Double inlet left ventricle (DILV) is a rare congenital cardiac anomaly characterized by a functionally univentricular atrioventricular connection, in which most or all atrial inflow is directed to the dominant, morphologic left ventricle via either two separate atrioventricular valves or a common atrioventricular valve. The second ventricle is typically a rudimentary (incomplete) morphologic right ventricle. While well-documented in humans, the occurrence of DILV in veterinary medicine remains poorly studied. This report describes a male European bison (Bison bonasus) that survived for 12 years with DILV and additional cardiac malformations. Surprisingly, despite the severity and complexity of these defects, the animal was culled for reasons unrelated to cardiac disease. A complete field necropsy was performed, but only the heart was subjected to further investigation. Due to specimen disruption, the heart was reconstructed with the assistance of pediatric cardiac surgeons and analyzed using post-mortem computed tomography imaging, which provided valuable insights into its anatomical structure and spatial relationships. This case highlights the importance of integrated pathology and advanced imaging in congenital heart disease, while acknowledging the practical limitations of ante-mortem investigations in free-ranging animals.