Update (July 3, 2026): Feline HCM — 2025 Review of Diagnostic Advances, Cardiac Myosin Inhibitors, and Rapamycin Trials (Beier, Vet Sci 2025)

Bottom line.

• A 2025 comprehensive review by Beier in Veterinary Sciences (open access, DOI 10.3390/vetsci12030289) synthesizes the latest clinical, diagnostic, and therapeutic advances in feline HCM, providing a practical update on a disease that affects approximately 14-15% of cats.
• Genetic mutations in sarcomeric genes (particularly MYBPC3) are well-evidenced in breed-associated HCM; however, the causal mutation for the majority of non-breed-specific HCM in domestic cats remains unidentified.
• Diagnostic advances discussed include contrast echocardiography, strain imaging (speckle-tracking), and the growing role of cardiac biomarkers (NT-proBNP, cardiac troponin I) in primary-care screening and progression monitoring.
• Emerging therapies reviewed include cardiac myosin inhibitors (mavacamten, aficamten — showing pharmacological activity in cats, but no approved veterinary product available), and rapamycin (an mTOR inhibitor with early evidence of HCM lesion reversal, in ongoing pivotal trials as of early 2025).
• This is a clinician-facing evidence summary. It is not a treatment protocol; confirm current product availability and clinical trial eligibility with a veterinary cardiologist.

Clinical facts

• Genetic architecture: MYBPC3 A31P (Maine Coon) and MYBPC3 R820W (Ragdoll) are the best-characterized breed-specific mutations; autosomal dominant with incomplete penetrance and variable expressivity. Commercial genetic tests are available for these two mutations. Negative test results do not exclude HCM in these breeds.
• Biomarker utility: NT-proBNP (SNAP Feline proBNP or laboratory assay): elevated values in apparently healthy cats identify those most likely to have cardiac disease on echocardiography. Cardiac troponin I (cTnI): marker of cardiomyocyte injury; elevated values correlate with severity and carry prognostic weight. Neither biomarker replaces echocardiography for diagnosis or staging.
• Diastolic dysfunction mechanisms: The 2025 review confirms that cardiomyocyte disarray, excessive collagen deposition, and microvascular disease all contribute to impaired myocardial relaxation and elevated filling pressures, producing the clinical syndrome of diastolic heart failure at the core of feline HCM.
• CHF and ATE frequency: The review confirms that approximately 15-25% of cats with HCM will develop CHF over a 10-year period, and approximately 10% will develop ATE — reinforcing existing staging guidance and thromboprophylaxis recommendations.

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What the evidence shows

Comprehensive 2025 review: where the field stands

Beier's 2025 review synthesizes existing evidence and the latest therapeutic developments in feline HCM across pathophysiology, genetics, diagnostics, and treatment.¹ The review confirms the phenotypic core of the disease — concentric hypertrophy, often asymmetric, predominantly affecting the left ventricle, with diastolic dysfunction arising from disordered cardiomyocyte alignment and excessive myocardial collagen — as established in current understanding. The genetic basis is strong for breed-associated disease (MYBPC3 mutations) and is the subject of ongoing investigation in mixed-breed cats.

Emerging diagnostic tools

The 2025 review discusses advancing diagnostic modalities beyond standard 2D echocardiography. Speckle-tracking echocardiography (myocardial strain imaging) can detect subclinical diastolic and systolic dysfunction before conventional echocardiographic criteria are met, offering potential as a tool for earlier identification of disease progression. Contrast echocardiography may improve characterization of SEC and left atrial thrombus. In primary-care settings, point-of-care NT-proBNP and cTnI assays continue to gain traction as triage tools for identifying cats with cardiac disease who should undergo referral echocardiography.

Emerging therapeutic landscape

The review provides an overview of novel therapeutic directions:¹

Cardiac myosin inhibitors: Mavacamten and aficamten (both approved in humans for symptomatic obstructive HCM) reduce hypercontractility by modulating the actin-myosin cross-bridge cycle. Both have demonstrated pharmacologic activity in cats, including acute LVOTO reduction with mavacamten in a small prospective case series of MYBPC3-positive cats, and an acceptable single-dose safety profile for aficamten. However, neither drug is approved for veterinary use, and feline-specific chronic dosing data are lacking.

Rapamycin: An mTOR inhibitor with evidence of reversing HCM lesions in cats in early studies. As of early 2025, a large-scale pivotal study across 20 US sites with 300 cats was reported to be underway; the drug was anticipated to seek FDA conditional approval. Practitioners should remain cautious — enrollment criteria, dosing, and monitoring requirements for clinical trials should be confirmed with a veterinary cardiologist or trial coordinator.

Persistent knowledge gaps

The review emphasizes that despite decades of research, no drug has been demonstrated to delay progression from preclinical to clinical HCM in cats, and the causal mechanisms for the majority of non-breed-specific feline HCM remain incompletely understood. This underscores the importance of continued monitoring and access to emerging trial data.

How this fits clinical practice

The Beier 2025 review is a useful update for practitioners to contextualize the current state of feline HCM beyond the established ACVIM consensus framework. The practical take-home points are: biomarkers (NT-proBNP, cTnI) have an expanding role in primary-care screening; new echocardiographic techniques (strain imaging) are approaching clinical relevance; and novel disease-modifying therapies (cardiac myosin inhibitors, rapamycin) are on the horizon but not yet approved for clinical veterinary use. The foundations of current management — echocardiographic diagnosis, ACVIM staging, thromboprophylaxis with clopidogrel for at-risk cats, and furosemide-based CHF management — remain unchanged.

Always confirm drug availability, trial eligibility, and emerging therapy indications with a board-certified veterinary cardiologist.

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References

1. Beier SL. 2025. Clinical-Diagnostic and Therapeutic Advances in Feline Hypertrophic Cardiomyopathy. Vet Sci 12(3):289. https://www.mdpi.com/2306-7381/12/3/289
2. Luis Fuentes V, Abbott J, Chetboul V, et al. 2020. ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats. J Vet Intern Med 34(3):1062-1077. https://onlinelibrary.wiley.com/doi/10.1111/jvim.15745

Changelog

• 2026-07-03: First published.