In order to describe the clinical characteristics of canine ventricular septal defect (VSD), we reviewed case records of patients that had been presented to one of two veterinary teaching hospitals in the Southeastern United States. Patients with a diagnosis of VSD were retrospectively identified through a search of medical records and the echocardiographic case log. For one institution1, the review period was May 1, 2000-December 31, 2004, and for the other2, January 1, 1991-December 31, 2004. Cases were included if a Doppler echocardiographic diagnosis of VSD was recorded. Complex malformations that include a VSD and constitute defined diagnostic entities such as tetralogy of Fallot and atrioventricular canal were excluded. Clinical findings were abstracted from the medical record. Breed predispositions were evaluated through calculation of odds ratios (OR) and associated 95% confidence limits (CL) using the unaffected caseload of one institution as the control sample. Case outcome as of December 2006 was determined from review of medical records and telephone calls placed to veterinary clients and referring veterinarians.
Fifty-three cases were identified of which 31 (59%) were male. Forty-seven (89%) patients were identified as one of 32 different pure breeds and 6 were mixed-breed dogs. The shiba inu (OR: 278 [95% CL: 94.47, 820.81]), bloodhound (OR: 37 [95% CL: 13.12, 106.16]), Old English sheepdog (OR: 20 [95% CL: 4.83, 85.05] and Chihuahua (OR: 6 [95% CL: 1.87, 19.38]) were amongst purebred dogs that were over-represented. The median (range) age at which the VSD was identified was 5 (2-132) months. Most (85%) patients were presented for evaluation of a subclinical heart murmur or for pre-breeding evaluation while 8 (15%) were presented because of family history or for evaluation of signs of tachypnea or exercise intolerance. Systolic murmurs were heard during examination of 45 (85%) of the patients while 7 (13%) had to-and-fro murmurs; 1 (2%) patient did not have a murmur. The arterial pulse was described as strong or bounding in 5 (9%) patients. The echocardiographic end-diastolic left ventricular dimension exceeded the upper limit of a published reference interval in 7 (13%) patients. Seven (13%) patients had moderate or severe aortic valve insufficiency. Associated lesions included pulmonary hypertension in 4 (8%), pulmonic stenosis in 5 (10%), subvalvular aortic stenosis in 5 (10%) and tricuspid valve dysplasia in 3 (6%). Four patients died or were euthanized as a result of heart disease; the median (range) age at the time patients were lost to follow-up, died of non-cardiac causes, or the study ended was 31 (2-151) months. Two (4%) VSD closed spontaneously.
Canine VSD often is benign. Breed predispositions are evident which suggests a genetic basis for the malformation in some cases.