T. C.F. Spanjersberg, A.H. Hulsman, G. C.M. Grinwis, B. Janssen, C. N. van der Wilt, R.J.A. Veltrop, C.J.B. Snijders Blok, C. Rozendom, P. J. Besseling, J. van der Velden, P. van der Harst, M. Harakalova, F. G. van Steenbeek; Phenotypic patterns in feline heart failure: A natural model for understanding variable disease severity in humans. iScience, v. 29, Issue 8, 2026, 116685, ISSN 2589-0042, DOI: 10.1016/j.isci.2026.116685.
Heart disease is one of the most common conditions affecting cats, with hypertrophic cardiomyopathy (HCM) being the most frequently diagnosed form. HCM causes the heart muscle to thicken, making it harder for the heart to pump blood effectively. While many cats with HCM may live for years with few symptoms, others develop life-threatening complications such as congestive heart failure or painful blood clots that can suddenly block blood flow to the hind legs. Scientists have long wondered why the same disease can lead to such different outcomes.
In this study, researchers examined heart tissue from 37 client-owned cats using advanced artificial intelligence (AI) technology and genetic analysis. The cats were divided into three groups: those that developed congestive heart failure, those that experienced arterial thromboembolism (ATE)—a serious blood clot—and cats with no known heart disease. By comparing these groups, the researchers hoped to uncover biological differences that could explain why heart disease progresses differently from one cat to another.
The researchers found that cats with blood clots had significantly more scar tissue (called fibrosis) within their heart muscle than cats in the other groups. This suggests that blood clots are not simply a later stage of heart disease but may represent a distinct form of the disease with its own pattern of tissue damage. The study also found subtle differences in the cells that make up the heart. Cats with heart failure had larger heart cell nuclei—a sign that the cells were adapting to increased stress—while cats with blood clots had larger numbers of smaller support cells, which may be linked to inflammation and tissue remodeling.
To better understand these changes, the researchers also studied which genes were active in the heart tissue. Hearts with more fibrosis showed reduced activity in genes involved in producing energy and conducting the electrical signals that keep the heart beating normally. Hearts with enlarged cell nuclei showed increased activity in genes that help cells respond to stress and repair damaged proteins. These findings suggest that different biological processes drive heart failure and blood clot formation, even though both develop from the same underlying disease.
One of the most exciting aspects of this study was the use of artificial intelligence to analyze thousands of microscopic features within the heart. AI allowed researchers to measure scar tissue, blood vessel changes, and individual cell characteristics much more accurately and consistently than traditional methods. This technology may help scientists identify disease patterns that would otherwise be difficult to detect.
Because cats naturally develop HCM in ways that closely resemble the disease in people, these findings may benefit both feline and human medicine. Unlike laboratory animals, companion cats develop heart disease spontaneously and experience many of the same complications seen in humans. Studying naturally occurring heart disease in cats gives researchers a valuable opportunity to better understand why some patients remain stable while others develop severe disease, ultimately helping guide future treatments for both species.
Why this research matters
Not every cat with hypertrophic cardiomyopathy follows the same path. This study shows that cats who develop heart failure and those who develop dangerous blood clots have different patterns of changes within their heart tissue. By identifying these differences, researchers are moving closer to predicting which cats are at greatest risk for specific complications and developing more personalized treatments. At the same time, this work strengthens the important role cats play in advancing heart disease research that could improve the lives of both cats and people.