Background: Tricuspid valve dysplasia (TVD) in dogs involves defects of the tricuspid valve, which result in changing degrees of blood leakage between the chambers of the right side of the heart. Dogs with the most severe malformations usually develop right-sided congestive heart failure within the first few years of life. Many dogs are only mildly affected at birth, and are not identified until after they have become breeding animals. Labrador Retrievers, in particular, seem to be predisposed to TVD. A previous study determined that TVD in one large pedigree of Labrador Retrievers was inherited as an autosomal dominant trait. Genetic analysis of these dogs mapped a susceptibility gene to canine chromosome 9, but the inheritance of this susceptibility gene was not simple, which agrees with an independent study on a larger population of dogs that did not reveal a simple mode of inheritance.

Objective: The researchers are continuing to examine Labrador Retrievers through clinical cardiology examinations, pedigree analysis, and DNA analysis, with the goal of identifying a mutant allele of a gene or genes responsible for TVD. Once found, genetic testing procedures can be developed to identify dogs at risk for developing clinical signs and for passing the disease to their offspring.