Hereditary Patent Ductus Arteriosus and Its Sequelae in the Dog

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Abstract
Further studies of hereditary patent ductus arteriosus (PDA) in the dog show the defect to have a graded phenotypic expression. A high proportion of offspring of test matings had a fully patent ductus arteriosus, while a smaller proportion had a blind diverticulum of the ductus arteriosus which communicated with the aorta. This is considered to be a forme fruste of PDA, representing incomplete closure. Approximately 50% of pups with fully patent ductus arteriosus developed signs of left heart failure, and about 15% developed severe pulmonary hypertension with right-to-left or bidirectional shunts. Genetic analysis indicated that hereditary PDA in the dog is not a simple mendelian trait, Rather, it resembles a quasi-continuous or threshold trait with a high degree of heritability. Results were analyzed using a polygenic model with two developmental thresholds. Liability to defective closure of the ductus arteriosus increased with the proportion of the genome received from dogs with PDA. Moreover, in pups which had PDA, the incidence of serious sequelae (left heart failure and severe pulmonary hypertension) increased in a parallel fashion, suggesting that an increased liability to PDA was accompanied by an increase in the severity of the lesion.