Acquired infundibular pulmonary stenosis associated with a congenital membranous ventricular septal defect (Gasul phenomenon) in a dog and discussion regarding causes of infundibular stenosis.

An aclinical Havanese dog was diagnosed with a membranous restrictive ventricular septal defect. The patient was represented later in their natural history due to the development of syncope. At that time the patient was diagnosed with acquired pulmonary infundibular stenosis. Balloon dilation of the stenosis was performed successfully twice over the patient's lifetime. The patient died suddenly approximately 14 months after the second balloon dilation. A discussion regarding primary infundibular pulmonary stenosis versus causes of acquired infundibular pulmonary stenosis including anomalous muscle bundles (double chamber right ventricle), tetralogy of Fallot, and infundibular stenosis is presented.