Congenital heart defects in cats – prevalence and survival : a retrospective study of 60 cats

Sammanfattning: Congenital heart disease (CHD) is defined as an anatomic defect of the heart or the associated great vessels present at birth. Depending on the severity of the defect, it may lead to heart failure, which generally results in a decreased quality of life and/or shortened life span. The prevalence of CHDs in cats in Sweden is not known and little is generally known about the expected lifespan of cats diagnosed with CHD. The purpose of this study was, therefore, to investigate the prevalence and distribution of CHD in a large group of cats presented at the University Animal Hospital in Uppsala, Sweden, between the years 1996 and 2013. In the first part of the study, case records of cats presented and diagnosed with CHD at the University Animal Hospital, Uppsala, between 1996 and 2013, were retrospectively reviewed. In total, 60 cats had been diagnosed with CHD during the study period. The prevalence of CHD was 0.2 % of the total number of visiting cats (n = 32 919), and 7.3 % of cats diagnosed with heart disease (n = 824). Ventricular septal defect (VSD) was the most common CHD accounting for 46.7% of cases, followed by tricuspid/mitral valve dysplasia (8.3%), aorta stenosis (8.3%), pulmonic stenosis (6.7%), Tetralogy of Fallot (6.7%), atrial septal defect (5 %) and mitral valve dysplasia, endocardial fibrosis, patent ductus arteriosus each accounting for approximately 1.7% of CHD cases. In 13.3% of the cats, more than one congenital heart defect was present. There was no sex predilection (P = 0.20). Because of the nature of the material for this study, namely too few individuals of the same breed, no breed predilection could be established. However, the group of domestic shorthair, which accounted for 46.7 % of all the cats, were more likely to have VSD than all purebred cats together (P = 0.008). For the second part of the study, follow-up telephone interviews with a standardised questionnaire, were conducted between the 24th of September and 8th of October in 2014. The aim was to reach all owners of cats that had been diagnosed with a CHD during the study period. However, 16 cats were lost to follow up because the owners could not be reached. Of the remaining cats, 31 had died and 13 were still alive, giving an estimated median survival time of 40 months. In total, 52 % of the cats had died from cardiac related disease. Their median survival time was 16 months, which was significantly shorter (P = 0.032) than cats that died from non-cardiac related disease with a median survival time of 35 months. Cats diagnosed with VSD had a median survival time of 123 months, which was significantly higher (P = 0.013) than cats diagnosed with other CHDs with a median survival time of 32 months. In conclusion, the prevalence and distribution of CHDs was shown to be consistent with findings in American and European literature on the subject, with VSD being the most common CHD, followed by tricuspid/mitral valve dysplasia and aortic stenosis. The result that domestic shorthair was more likely to have VSD than purebred cats may be true for the whole cat population but can also be an reflection of the nature of the study population, hence more studies are needed. The fact that cats diagnosed with VSD had a markedly longer expected survival time than cats diagnosed with other CHDs is interesting from a clinical point of view, especially when considering that only one cat, out of nine dead cats with VSD, died because of cardiac related disease. This confirms the general empirically based idea that cats diagnosed with VSD have a relatively good long-term prognosis.