Hypertrophic cardiomyopathy (HCM) often goes undiagnosed until a cat is in heart failure. Understanding HCM can help early disease detection and client education.
Hypertrophic cardiomyopathy (HCM) is by far the most common type of heart disease diagnosed in cats. The disease is difficult to detect when a cat has no obvious clinical signs. That means most cats are diagnosed when they have signs of congestive heart failure, arterial thromboembolism or even sudden death.
Despite the prevalence of hypertrophic cardiomyopathy, we’re still learning more about the disease, how to treat it and how to accurately diagnose it before the condition becomes life-threatening. Results from a study funded by Morris Animal Foundation offer new hope that a simple screening to detect HCM early can improve treatment and outcomes.
Thorough physical examinations are the cornerstone of veterinary appointments, but several studies have shown that few cats with subclinical heart disease have telltale physical exam abnormalities. For example, most practitioners know the presence or absence of a heart murmur doesn’t mean a cat has or doesn’t have hypertrophic cardiomyopathy. While the presence of a heart murmur typically triggers further testing, such as echocardiography, detecting occult heart disease remains difficult.
Echocardiography is the gold standard for diagnosing hypertrophic cardiomyopathy in cats. Elizabeth Rozanski, DVM, ACVIM, ACVECC, and colleagues at Tufts University knew that several barriers to this test exist including cost, proximity to a boarded cardiologist, and the skillset and equipment required to perform a full echocardiogram. They were also aware that focused cardiac ultrasound (FCU) was gaining popularity in human hospital emergency rooms as a quick way to assess patients for serious cardiac conditions. Dr. Rozanski wanted to determine if a non-specialist practitioner (NSP) could be trained to perform FCU to increase detection of occult heart disease in cats.
NSP Training and Results
Dr. Rozanski and her team developed an FCU protocol and trained 22 NSPs to perform the procedure. The NSPs screened 289 cats without signs of heart disease. All patients had follow-up echocardiograms by a board-certified cardiologist.
Dr. Rozanski found that the NSPs were very good at detecting moderate and severe heart disease in the study population. They were less skilled at detecting mild disease, but Dr. Rozanski was encouraged by the results and hopes more practitioners can learn FCU and incorporate it into their practice. Dr. Rozanski published her results in the Journal of Veterinary Internal Medicine.
Further research into HCM
Another important project funded by Morris Animal Foundation centered on hypertrophic cardiomyopathy was the REVEAL study. Published in 2018, the study was a collaborative effort among veterinary cardiologists at 50 veterinary hospitals located in 21 countries. In total, 1,730 cats were examined over a 10-year period. Philip Fox, DVM, MS, DACVIM/ECVIM (cardiology), DACVECC, the lead author of the study and a Foundation-funded grantee, was curious to learn more about the natural history of occult hypertrophic cardiomyopathy. He felt that because prior studies often were located at one referral facility and generally focused on cats with severe disease, results were skewed toward adverse outcomes and short survival. Dr. Fox wanted to learn more about the outcomes for cats who had HCM but were preclinical.
Dr. Fox, who is Head of Cardiology at the Animal Medical Center in New York City, and colleagues compared cats with asymptomatic hypertrophic cardiomyopathy to apparently healthy cats. The cats with hypertrophic cardiomyopathy were further divided into cats with nonobstructive or obstructive forms of hypertrophic cardiomyopathy. The study found that during the study period, congestive heart failure or arterial thromboembolism (or both) occurred in 30.5% of cats with either form of HCM. The study also noted that cardiovascular death occurred in 27.9% of cats with either form of hypertrophic cardiomyopathy. His conclusion was that cats with HCM had a high risk of morbidity and mortality. Interestingly, the study did not find a significant difference in morbidity or morality between cats with nonobstructive and those with obstructive forms of hypertrophic cardiomyopathy. Dr. Fox published his findings in the Journal of Veterinary Internal Medicine.
Although we’re making progress, we still have a lot to learn about hypertrophic cardiomyopathy in cats. Early detection is important for long-term monitoring of patients and for client education. Unfortunately, there remains a significant knowledge gap in understanding which preventive measures, if any, can delay onset of clinical signs or improve long-term survival. Morris Animal Foundation continues to support research in this important area of feline medicine. Our hope is that we can fill this knowledge gap and improve the lives of cats everywhere.