Hypertrofisk kardiomyopati hos Maine coon katter

Abstract: Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats. Maine coon is one of the breeds where the disease is overrepresented. Studies have shown that HCM is inherited as an autosomal dominant trait in Maine Coon cats. This finding has led to cardiac screening using ultrasound in the breed. The results of the screening are used in a national breeding program constructed to reduce the spread and incidence of HCM in Maine Coon cats. The disease is characterized by a broad range of phenotypic patterns which leads to difficulties in interpretation of the ultrasonographic findings and classification of cats in the breeding program. This study reports of different phenotypes in Maine Coon cats which were screened at the Department of Medicine and Surgery during the period January until November 2003. A screening protocol designed by M. D. Kittleson was used to evaluate the cats. It includes a physical examination, ultrasound examination and provides guidelines for the diagnosis of HCM. Thus, depending on the findings in a particular cat, it may be classified as normal, equivocal or HCM. In total, seventeen cats were examined. Four of these cats were diagnosed as equivocal regarding HCM, indicating that the changes in the heart are either an early stage of HCM or a normal phenotype. All the four cats in the equivocal group were classified based on the finding of papillary muscle hypertrophy. The thirteen remaining cats where diagnosed as normal. Nine of these thirteen cats had cardiac anatomical changes interpreted as a normal phenotype. Thus, the proportions cats in which some form of cardiac change were noted (most of them non-pathological changes) or were classified as equivocal were high. Obviously, this complicates the diagnosis. To decide on diagnosis in equivocal cats, several cardiac examinations over time are often required. During this time period, the use of this particular cat for breeding is restricted. Heart changes in equivocal cats can be a normal phenotype and accordingly, there is a potential risk of keeping healthy cats from breeding. When animals are excluded from breeding, this limits the genetic material and increases the risk of selection of cats with other genetic disease. Thereby, it is appropriate as a first step towards a healthier breed, that only cats with diagnosis HCM are excluded from breed.