In a November 2011 report in an upcoming issue of the Veterinary Journal, UK researchers state that they failed to find genetic differences between early-onset and late-onset MVD in 36 cavaliers. Nor did they find loci associated with mitral valve murmur in a genome-wide association study.

But, in September 2011, another team of researchers, studying 241 CKCSs, reported in the Journal of Heredity that they identified two specific locations on cavaliers' chromosomes CFA13 and CFA14 which are associated the breed's hereditary mitral valve disease.

So, what's up? See the details here