Sadly, there are studies, one of which I am reading right now, which confirm that this very popular cat breed (particularly the blue) suffers from a high prevalence of HCM, often of early onset and with a significant male sex predisposition. In other words, male cats are predisposed to get it at a young age.
The study that I am reading is entitled: “Prevalence of Hypertrophic Cardiomyopathy in a Cohort of British Shorthair Cats in Denmark”. It was published in 2011. So, the cat fancy appears to have been aware of this inherited disease for at least 11 years and more. To the best of my knowledge, the only way to remove a genetically inherited disease from a cat breed is to remove breeding cats that suffer from the disease from the breeding lines. You simply have to remove all those cats that are predisposed to the disease from all breeding lines. This is something which has not happened unless someone can helpfully correct me.
Note: another study: “Feline Hypertrophic Cardiomyopathy: A Spontaneous Large Animal Model of Human HCM” (2017), states: “Cats are most commonly affected by hypertrophic cardiomyopathy (HCM), with a prevalence of 10-15% in the general pet cat population. However, breeds such as the Maine Coon cat, Persian, Ragdoll, and Sphynx are at higher risk”. Therefore, the British Shorthair is no worse than the general domestic cat population. That does not prevent reducing or eliminating from breeding lines.
A total of 329 British Shorthair cats were examined. There were 214 females and 115 males. Their median age was 2.3 years with a range of 0.8 years to 14.1 years old.
28 of the cats representing 8.5% were classified as HCM positive. They decided that 14 of the cats (4.3%) were equivocal, which I take to mean borderline and 282 (85.7%) were assessed as being HCM negative. In addition, 2.1% were diagnosed as suffering from other cardiac diseases.
RELATED: Cat breeds prone to HCM
Male British Shorthair cats, in this study, “had a significantly higher occurrence of HCM (20.4%) compared with the females (2.1%).
The scientists decided that this cat breed “had a high incidence of HCM”.
Hypertrophic homeopathy is the most commonly diagnosed heart disease in domestic cats. It is characterised by a left-ventricular concentric hypertrophy and systolic dysfunction in the absence of other cardiac or systemic disorders that may cause left ventricle concentric hypertrophy.
I have a book on inherited diseases suffered by cat breeds: Medical, Genetic and Behavioural Aspects of Purebred Cats by Ross D Clark DVM. He does not mention that the British Shorthair cat is predisposed to HCM. The book was published in 1992. It would appear that the prevalence of this disease became noticeable in the early 2000s.
He reports that haemophilia B “has been reported in British shorthaired cats”. He also reports on another disorder “found more commonly in British shorthair cats than in other breeds” namely neonatal erythrolysis.
The scientists conducting the study were:
S. Granström, M.T. Nyberg Godiksen, M. Christiansen, C.B. Pipper, J.T. Willesen, J. Koch
Below are some more pages on the British Shorthair.