Incomplete atrioventricular septal defect as an incidental finding in an African lion (Panthera leo) cub during an acute multi-organ crisis: case report

Background Congenital heart defects are reported less often in non-domestic than in domestic species, although reports now span felids, primates, ungulates, and marine mammals. Atrioventricular septal defects (AVSDs), which arise from abnormal development of the endocardial cushions, are among the less frequently reported congenital heart defects in animals. Case description A 137-day-old female African lion cub (13.14 kg) was presented with generalized weakness, incoordination, dyspnea, and dehydration. Initial investigations revealed severe hypoglycemia, hemoconcentration, marked hepatocellular and muscle enzyme elevation, hyperkalemia, and an elevated cardiac troponin I concentration (8.9 ng/mL). Transthoracic echocardiography, performed after metabolic stabilization, incidentally identified a 2.2-cm defect in the primum portion of the atrial septum adjacent to the atrioventricular valves, consistent with an incomplete AVSD, with predominant left-to-right shunting and right ventricular volume overload. An agitated saline study additionally demonstrated a right-to-left shunt component. Despite supportive care, the cub developed azotemia and conjugated hyperbilirubinemia and died on day 4. Necropsy confirmed a 2 × 2.5-cm defect extending from the mid-atrial septum to the atrioventricular valves, right heart volume overload, right ventricular interstitial fibrosis, and multi-organ damage. Conclusion The incomplete AVSD in this cub was an incidental finding during a systemic illness, and its contribution to the fatal outcome cannot be determined. To the authors’ knowledge, this is the first report of an AVSD in a lion.