Case Studies In Small Animal
Tricuspid atresia with an ASD and a VSD in a kitten
View looking down on the right atrium (no tricuspid valve is present and a large atrial septal defect [ASD] is seen toward the top)
View looking down on the right atrium (no tricuspid valve is present)
A view of the atrial septal defect
A view of the ventricular septal defect (VSD) from the left side. The VSD lies immediately beneath the aortic valve.
A view of the ventricular septal defect (VSD) from the left side. The VSD lies below the pulmonic valve, in the right ventricular outflow tract. This is an unusual location for a VSD.
This kitten was found in a trash can by a Good Samaritan and taken to a veterinary hospital. The veterinarian that examined the kitten, Dr. Roemer, estimated the kitten to be 8 to 10 weeks of age. At presentation it was in bad shape with a severe upper respiratory infection. It was also noted to be cyanotic. On physical examination a systolic heart murmur was ausculted. An echocardiogram was performed and a ventricular septal defect was identified. Despite appropriate therapy the kitten died in the hospital that night.
On post mortem examination the kitten had no tricuspid valve (tricuspid valve atresia). In order for it to live even a short while, there had to be relatively large communications between the left and right sides of the heart. The large atrial septal defect allowed blood returning from the body (systemic venous blood) to shunt from the right atrium to the left atrium and ventricle (right-to-left shunt). At the ventricular level, the ventricular septal defect (VSD) allowed blood then to shunt back again to the right ventricle (left-to-right shunt) and so then to the pulmonary circulation to be oxygenated. During early life the ductus arteriosus would have been patent and would have helped shunt blood flow to the pulmonary circulation.
Amazingly this kitten lived for a couple of months after birth with a relatively small VSD and no patent ductus arteriosus. The cyanosis that was present meant the kitten's arterial oxygen tension was in the 30 to 45 mmHg of range, mostly due to the right-to-left shunt at the atrial level and the inadequate left-to-right shunt at the ventricular level. However, the upper respiratory infection almost certainly compromised the ability of the kitten to adequately oxygenate itself and almost certainly contributed to this kitten's demise.
©Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.