Hereditary congenital heart defects in dogs

Congenital heart defects is probably the most common class of malformations found in dogs, occurring with a frequency approaching 1 per cent in animals presented to veterinary clinics. The frequency is significantly higher among purebred dogs than in dogs of mixed breeding and specific anatomic malformations occur with highest frequency in certain breeds. Genetic studies of patent ductus arteriosus, pulmonic stenosis, subaortic stenosis, ventricular septal defect, tetralogy of Fallot and persistent aortic arch have confirmed that these are specific heritable defects, the genes for which are concentrated in a number of different breeds. Each of these defects is inherited in a complex manner consistent with a polygenic basis. This paper will describe evidence supporting the view that the common forms of congenital heart disease in the dog are polygenic threshold traits. The general criteria for recognition of polygenic traits and methods for their control will be discussed.