The 60-second check that can change outcomes for HCM patients

By Heather Davis, DVM, PhD, DACVS-LA

Hypertrophic cardiomyopathy (HCM) is the most common cardiovascular disease in domestic cats, affecting approximately one in seven, and it remains the leading cause of mortality in adult cats nine years of age and older.^1,2 Despite its prevalence, HCM is notoriously difficult to identify in a clinical setting. Many affected cats remain subclinical for years, showing no outward signs of disease until they present acutely with congestive heart failure (CHF), arterial thromboembolism, or sudden cardiac death.³ For the practicing veterinarian, this clinical reality has historically presented a significant challenge: identifying cats at risk and monitoring them through a disease process that often progresses silently between visits.

Until recently, management of subclinical HCM centered on watchful waiting. Once a diagnosis was established via echocardiography, options were largely limited to periodic re-evaluation and client counseling. That landscape is beginning to change, and alongside emerging pharmacologic therapy, one of the most underutilized tools in feline cardiology is something a client can do at home in 60 seconds: sleeping respiratory rate (SRR) monitoring.

Why SRR matters

A healthy cat's SRR typically falls below 30 breaths per minute in the home environment, and published studies demonstrate cats with subclinical heart disease, including HCM, generally maintain stable values below that threshold.^4,5 When SRR begins to rise persistently, it may signal developing pulmonary edema or pleural effusion before the cat exhibits overt clinical signs of respiratory distress.

The clinical value of home-based respiratory rate measurement lies in its ability to capture true baseline cardiopulmonary function. Respiratory rates recorded during in-clinic examinations are frequently elevated by transport, handling, and stress-associated sympathetic activity. SRR measurements taken while a cat is genuinely asleep in its home environment minimize these confounders and more accurately reflect the physiologic baseline.⁴

This principle has precedent in canine cardiology. In dogs with preclinical myxomatous mitral valve disease, rising resting respiratory rates have been shown to identify impending CHF days before overt respiratory distress develops.⁶ The same pathophysiologic principle applies in feline cardiac patients. A client who identifies a sustained increase in SRR and contacts the clinic during routine hours represents a fundamentally different clinical situation than an owner presenting to an emergency facility with a cat in acute respiratory crisis.

Integrating SRR monitoring into clinical practice

Timing of client education matters. The appointment at which an HCM diagnosis is first communicated is not the optimal time to introduce a detailed home-monitoring protocol; the client is still processing clinical information and grappling with prognostic uncertainty. A more effective approach is to introduce the concept briefly at diagnosis and reserve detailed instruction for the follow-up visit.

At the recheck appointment, teaching SRR monitoring requires approximately five minutes of clinical time. The cat must be genuinely asleep, not simply resting with eyes closed. Purring should disqualify the measurement, as it alters the respiratory pattern.⁵ Each complete chest rise and fall constitutes one breath. A 30-second count multiplied by two is sufficient, although a full 60-second measurement provides greater accuracy. Owners may elect to video-record the measurement for retrospective counting if preferred.

Establishing an individualized baseline is essential. Clients should be encouraged to collect two to three measurements per week during the first several weeks to define a cat-specific norm. While the published clinical threshold is 30 breaths per minute, an individual cat may routinely maintain 16 or 24 breaths per minute at baseline. Knowing that specific value makes subsequent deviation easier to identify.⁷

Clients should also be counseled that a single elevated reading does not constitute an emergency. Transient elevations may reflect light sleep, ambient temperature, or measurement error. Owners should confirm elevated values across two to three consecutive measurement sessions before contacting the clinic.^6,7 However, a persistent SRR above 30 breaths per minute, or a sustained increase of 20 percent or more above a cat's established baseline, warrants timely veterinary assessment.

Changing the dynamic

Beyond its clinical utility, SRR monitoring meaningfully reshapes the relationship between the client and the veterinary care team. An HCM diagnosis can leave owners feeling helpless, as the disease is largely invisible between clinical visits, and long-term outcomes can be uncertain. Providing the client with a structured, low-burden home task gives them an active role in their cat's care and reinforces the collaborative nature of chronic disease management.

When an owner presents at a recheck appointment with documented SRR data, whether recorded in a notebook, a phone application, or a notes app, the clinical conversation shifts. The owner becomes a participant in monitoring rather than a passive recipient of information. Clients who feel included in monitoring are more likely to attend follow-up appointments and to contact the clinic early when trends change.

Data shared between visits, whether by phone, email, or practice portal, can also inform clinical decision-making without requiring an in-person evaluation for every concern. A gradual upward trend may prompt an expedited recheck, a medication adjustment, or reassurance that values remain within an acceptable range. This type of proactive, data-informed communication supports long-term client trust and is increasingly feasible within modern practice workflows.

An evolving therapeutic landscape

The case for structured home monitoring has only strengthened as the therapeutic landscape for feline HCM has begun to evolve. For decades, management of subclinical HCM was limited to monitoring and supportive care, as no pharmacologic intervention was approved to address the underlying disease process.⁸

That has changed. Research into the mammalian target of rapamycin (mTOR) pathway has identified a mechanism by which dysregulated cellular signaling drives pathologic ventricular hypertrophy, and clinical trial data have demonstrated that targeted mTOR inhibition can slow or halt the progression of left ventricular wall thickening in cats with subclinical HCM.^9,10 The U.S. Food and Drug Administration (FDA) has granted conditional approval to Felycin-CA1 (sirolimus delayed-release tablets), the first and only disease-modifying drug conditionally approved by the agency to manage HCM.¹¹ Currently, a large multicenter pivotal trial (HALT HCM) is currently underway to generate the data required to support its full approval.¹¹

As additional therapeutic options enter clinical practice, the rationale for structured home monitoring becomes more compelling. Cats receiving ongoing therapy require consistent follow-up to assess response, and SRR monitoring provides an accessible, low-burden mechanism for owners to contribute clinical data between echocardiographic re-evaluations. A stable or declining trend may offer reassurance; a rising trend may warrant earlier assessment. In either case, the data is clinically actionable, and the owner generates it in the home environment at no cost.

Home monitoring also complements screening efforts in cat breeds with documented predisposition to HCM, including Maine coons, ragdolls, British shorthairs, Persians, and Sphynxes.^1,2 There is no clinical reason SRR monitoring cannot be introduced to owners of at-risk breeds prior to a formal diagnosis, as part of routine wellness counseling. Broader adoption of the practice across the cat-owning population supports earlier detection of cardiac decompensation in cats whose baseline values begin to shift.

A foundational practice worth five minutes

Teaching a client to count their cat's sleeping breaths takes approximately five minutes of clinical time. The data yielded by that brief instruction can inform months of clinical decision-making, support earlier intervention, and strengthen the collaborative relationship that underpins effective chronic disease management. With new therapies entering the clinical toolkit, expanded screening recommendations, and pivotal trials underway, SRR monitoring is a foundational practice that costs nothing, carries no risk, and has the potential to meaningfully change outcomes for feline HCM patients.

The next time a client asks what can be done for their cat after an HCM diagnosis, the answer can begin with something simple and actionable: watching their cat sleep.

Heather Davis, DVM, PhD, DACVS-LA, is the senior director of Medical Affairs and Veterinary Services at Pegasus Laboratories/PRN Pharmacal, where she supports the development and clinical integration of innovative therapies for companion animals. She can be reached at hdavis@pegasuslabs.com.

References

1. Payne JR, Brodbelt DC, Luis Fuentes V. Cardiomyopathy prevalence in 780 apparently healthy cats in rehoming centres (the CatScan study). J Vet Cardiol. 2015;17(Suppl 1):S244-S257.
2. Kittleson MD, Meurs KM, Harris SP. The genetic basis of hypertrophic cardiomyopathy in cats and humans. J Vet Cardiol. 2015;17(Suppl 1):S53-S73.
3. Fox PR, Keene BW, Lamb K, et al. International collaborative study to assess cardiovascular risk and evaluate long-term health in cats with preclinical hypertrophic cardiomyopathy and apparently healthy cats: The REVEAL Study. J Vet Intern Med. 2018;32(3):930-943.
4. Ljungvall I, Rishniw M, Porciello F, Häggström J, Ohad D. Sleeping and resting respiratory rates in healthy adult cats and cats with subclinical heart disease. J Feline Med Surg. 2014;16(4):281-290.
5. Porciello F, Rishniw M, Ljungvall I, et al. Sleeping and resting respiratory rates in dogs and cats with medically-controlled left-sided congestive heart failure. Vet J. 2016;207:164-168.
6. Ohad DG, Rishniw M, Ljungvall I, Porciello F, Häggström J. Sleeping and resting respiratory rates in dogs with subclinical heart disease. J Am Vet Med Assoc. 2013;243(6):839-843.
7. VCA Animal Hospitals. Home breathing rate evaluation. Accessed April 2026. https://vcahospitals.com/know-your-pet/home-breathing-rate-evaluation
8. S. Food and Drug Administration. FDA conditionally approves drug for management of ventricular hypertrophy in cats. March 14, 2025. Accessed April 2026. https://www.fda.gov/animal-veterinary/cvm-updates/fda-conditionally-approves-drug-management-ventricular-hypertrophy-cats
9. Kaplan JL, Rivas VN, Walker AL, et al. Delayed-release rapamycin halts progression of left ventricular hypertrophy in subclinical feline hypertrophic cardiomyopathy: results of the RAPACAT trial. J Am Vet Med Assoc. 2023;261(11):1628-1637.
10. Stern JA, et al. Multi-omic, histopathologic, and clinicopathologic effects of once-weekly oral rapamycin in a naturally occurring feline model of hypertrophic cardiomyopathy: a pilot study. 2023;13(19):3014.
11. TriviumVet secures FDA conditional approval for first treatment for feline cardiac disease. March 2025. Accessed April 2026. https://www.triviumvet.com/blog/triviumvet-secures-fda-conditional-approval-for-feline-cardiology-disease