Disappearance of Shunt Flow after a Ventricular Septal Defect became Covered by a Cyst on the Fibrous Ridge at the Left Ventricular Outflow Tract of Subaortic Stenosis in a Dog

Abstract

A four-month-old female Siberian Husky weighing 13 kg was referred to the Animal Clinical Research Foundation Hospital with a suspicion of congenital heart problem. The suspicion was based on the presence of heart murmur identified during a physical checkup prior to vaccination at the referring hospital. The dog was diagnosed by echocardiography and cardiac catheterization as having membranous ventricular septal defect (VSD) and subaortic stenosis. But the condition of the dog was not so serious, and surgical treatment was judged to be unnecessary. Instead, periodical checkups were done until the dog died at the age of ten years. During this time no medication was given. No significant change in the heart condition was noted morphologically or functionally on echocardiographs or radiographs until the dog received a checkup at the age of nine years, when the shunt flow caused by the VSD was no longer seen on echocardiograms. Necropsy showed that a cyst developed partially from the fibrous ridge at the left ventricular outflow tract blocking the VSD, and resulting in the disappearance of the shunt flow of the VSD.