Double-outlet right ventricle with contrasting hemodynamic phenotypes in two dogs: two case reports

A double-outlet right ventricle (DORV) is defined as complete or predominant origin of both great arteries from the right ventricle and is almost always associated with a ventricular septal defect (VSD). Although DORV shows marked heterogeneity in humans, it is rare in veterinary medicine, with only a limited number of reported cases. This study evaluated 2 dogs with distinct hemodynamic characteristics. Case 1 was a 3-year-old Shiba Inu with DORV, a large subaortic perimembranous VSD, subaortic stenosis, and severe pulmonary hypertension. Despite the elevated pulmonary arterial pressure, left-to-right shunting predominated because of elevated left ventricular systolic pressure secondary to subaortic stenosis. Case 2 was a 5-year-old mongrel dog with a subaortic perimembranous VSD, in which the aortic root showed approximately 50% dextroposition and was mostly connected to the right ventricular component of the heart, leading to a diagnosis of DORV. Severe pulmonary hypertension and a bidirectional VSD shunt with dominant right-to-left flow were consistent with the Eisenmenger physiology. These cases revealed the structural diversity of canine conotruncal anomalies and highlight the importance of detailed echocardiographic assessment.