Transitional Atrioventricular Septal Defect in a Dog: From Embryological and Terminology Perspectives

A 7-year-old, 2.6 kg, spayed female Maltese dog was referred for suspected congenital heart disease.The clinical signs included tachypnea, mild exercise intolerance, and cyanosis.Following echocardiography, the dog was diagnosed with a transitional atrioventricular septal defect (AVSD).The dog was also diagnosed with pulmonary hypertension due to congenital heart disease, which was likely secondary to volume overload caused by a large atrial septal defect.Management solely with sildenafil alone has produced favorable outcomes.This case report discusses transitional AVSD from the perspectives of terminology and embryology.