Feline HCM ACVIM Consensus Screening: Maine Coon, Ragdoll, Sphynx, Persian

Last updated: May 23, 2026

What Feline HCM Is and Why Screening Matters

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats, affecting somewhere around 15 percent of the general adult cat population in various estimates and substantially higher in predisposed breeds. The disease is characterized by thickening of the left ventricular wall and interventricular septum, often with associated diastolic dysfunction, left atrial enlargement, and risk of thromboembolic complications including feline aortic thromboembolism (FATE). Some cats live their entire lives with HCM and never develop clinical signs. Others progress rapidly to heart failure or sudden death.

In 2020, Luis Fuentes and colleagues published the ACVIM consensus statement on the classification, diagnosis, and management of cardiomyopathies in cats (Journal of Veterinary Internal Medicine). The consensus established a staging framework analogous to the canine ACVIM mitral staging we cover in ACVIM mitral staging. The feline framework provides clarity for clinical decisions, screening, and adopter education.

For broader background, see hypertrophic cardiomyopathy in cats for the disease overview and clinical signs.

The ACVIM 2020 Staging Framework

The Luis Fuentes consensus defined five stages of feline cardiomyopathy:

• Stage A — at-risk cat with no echocardiographic abnormality. Includes predisposed breeds (Maine Coon, Ragdoll, Sphynx, Persian, British Shorthair, Norwegian Forest Cat, others) and cats with first-degree relatives diagnosed with cardiomyopathy.
• Stage B1 — mild left ventricular hypertrophy without left atrial enlargement. No clinical signs.
• Stage B2 — left ventricular hypertrophy with left atrial enlargement. No clinical signs but increased risk of thromboembolic disease and progression to heart failure.
• Stage C — current or prior congestive heart failure or thromboembolic disease.
• Stage D — refractory congestive heart failure despite optimized therapy.

Stage classification drives treatment, surveillance, and prognostic conversations. Stage A cats receive periodic monitoring without medication. Stage B1 cats are monitored more closely with periodic echocardiography. Stage B2 cats — the threshold where left atrial enlargement signals elevated thromboembolic risk — are candidates for clopidogrel for FATE prevention. Stage C management combines diuretics, ACE inhibitors, and supportive care. Stage D triggers advanced management conversations including quality-of-life-first discussions.

Breed-Specific Genetics

Several feline breeds carry identified MYBPC3 (cardiac myosin binding protein C) gene variants that increase HCM risk:

• Maine Coon — A31P variant identified by Meurs and colleagues; A74T variant also described. Genetic testing widely available through OFA-listed labs, Wisdom Panel Cat, Optimal Selection, and Vetnostic.
• Ragdoll — R820W variant in MYBPC3 identified; testing available through the same commercial labs.
• Sphynx — a variant has been identified in research populations; commercial testing may be more limited depending on lab.
• Persian, British Shorthair, Norwegian Forest Cat, others — predisposed by breed pattern; specific variants in these breeds are less fully characterized as of current literature.

Genetic testing is informative for breeding decisions and individual risk assessment. Penetrance is incomplete — homozygous positive Maine Coons can have normal hearts well into adulthood, and homozygous negative cats can occasionally develop HCM through other mechanisms. The practical interpretation: a positive test increases risk and tightens surveillance; a negative test does not eliminate it. Annual echocardiographic screening remains the cornerstone for at-risk breeds.

The Screening Schedule

For at-risk breeds and breeding programs, the typical screening schedule includes:

• Annual echocardiography by a DACVIM-Cardiology or experienced sonographer beginning in young adulthood (often around age 1 to 2 for breeding cats, later for pet cats). Measurements focus on LV free wall thickness, interventricular septum thickness, left atrial size, and indices of diastolic function.
• NT-proBNP testing as a supporting biomarker for screening, particularly useful in less-accessible settings or as a triage tool. See NT-proBNP biomarker interpretation.
• Cardiac troponin I as an additional injury marker in selected cases.
• Genetic testing for breed-relevant variants.
• Annual physical exam with attention to gallop rhythm, murmur, or arrhythmia. Many HCM cats have no audible murmur, which is why physical exam alone is insufficient.

The challenge with feline echocardiography is technical difficulty — small fast hearts, stressed patients, and the false-positive trap of stress-induced transient myocardial thickening (called “transient myocardial thickening” in the literature). A calm exam, minimal restraint, and DACVIM-Cardiology interpretation reduce these errors. We cover the technical side in veterinary echocardiography.

The FAT-CAT Trial and Clopidogrel for Stage B2

The FAT-CAT trial (Hogan and colleagues), published in the Journal of Veterinary Internal Medicine, addressed one of the most feared complications of feline HCM: feline aortic thromboembolism. Cats with left atrial enlargement are at substantially elevated risk of thrombus formation in the left atrium with potential dislodgement and arterial embolization — most commonly to the iliac bifurcation, producing painful hindlimb paresis or paralysis. FATE is a devastating event for cats and their families. See feline aortic thromboembolism FATE for clinical details and emergency recognition.

FAT-CAT compared clopidogrel to aspirin in cats with cardiomyopathy and prior thromboembolic events. Clopidogrel was associated with longer time to recurrent thromboembolism and better outcomes. The clinical translation: clopidogrel is the antiplatelet of choice for FATE prevention in Stage B2 and Stage C HCM cats with left atrial enlargement. The DACVIM-Cardiology determines initiation timing and dosing.

HCM with Left Ventricular Outflow Obstruction

A subset of HCM cats have dynamic left ventricular outflow tract obstruction (LVOTO) — systolic anterior motion of the mitral valve produces a subaortic flow disturbance that can be heard as a murmur and produces additional hemodynamic burden. LVOTO subtype affects medication decisions:

• Atenolol — a beta-blocker that reduces heart rate and contractility, potentially reducing LVOTO severity.
• Pimobendan use is controversial in HCM with significant LVOTO — its positive inotropic effect may worsen outflow obstruction. The cardiologist makes individualized decisions.
• Diltiazem — calcium channel blocker sometimes used in HCM, especially with poor relaxation.

Distinguishing obstructive from non-obstructive HCM matters for therapy selection. Echocardiographic assessment of LVOTO with color Doppler and spectral Doppler characterizes the obstruction and guides medication choice.

Stage C and D Management

When a cat develops congestive heart failure (Stage C), management typically includes furosemide for diuresis, ACE inhibitors or angiotensin receptor blockers, clopidogrel for FATE prevention if Stage B2 progressed, and supportive care. Cat-specific cardiac drugs include benazepril, spironolactone, and amlodipine when systemic hypertension co-exists. Quality-of-life conversations become central. Cats are sensitive to medication side effects and require careful titration.

Stage D — refractory CHF despite optimal therapy — is the most challenging chapter. Care intensifies with attention to comfort, nutrition, and family planning. Acute decompensation triggers ER stabilization with oxygen, diuretics, and careful handling to minimize stress. The transition to hospice care, when appropriate, is covered by the broader hospice framework.

Anesthesia Considerations for HCM Cats

HCM cats — particularly those with LVOTO — carry elevated anesthesia risk. Hypotension worsens outflow obstruction and can trigger life-threatening arrhythmia. Pre-anesthetic workup with echocardiography, careful drug selection avoiding ketamine alone in HOCM patients, and continuous monitoring are essential. We cover the framework in cardiac patient anesthesia consensus for the ACVAA and ACVIM-Cardiology joint approach.

What Adopters Should Know

Many cats in shelters and rescues are wonderful adoption candidates regardless of HCM risk. The realistic preparation includes:

• Recognize that all adult cats face baseline HCM prevalence; predisposed breeds carry higher risk but the disease occurs in all genetic backgrounds.
• Ask the shelter or rescue about murmur findings or echo history; many shelters cannot afford specialty workup, which is normal.
• Budget for annual veterinary exam with auscultation; if a murmur or gallop is detected, follow with echocardiography.
• Plan for NT-proBNP testing as an affordable screening adjunct in predisposed breeds.
• Recognize FATE warning signs — sudden hindlimb weakness or paralysis, vocalization, cold limbs. This is an emergency.
• Connect with a primary veterinarian comfortable with feline cardiac care, and identify cardiology referral or telemedicine access.

Cats with Stage B1 or B2 HCM often live many years with appropriate monitoring and Stage B2 clopidogrel for FATE prevention. The diagnosis is not a dealbreaker. Many adopters take on HCM-positive cats and provide exceptional homes, with informed planning and quality-of-life-first values.

Cost and Specialty Access

Feline echocardiography costs vary by region and specialist, generally in a several-hundred-dollar range. Genetic testing is a one-time modest expense through OFA-listed labs. NT-proBNP and cardiac troponin I are affordable send-out tests. Long-term medication costs depend on stage and specific regimen.

If a board-certified veterinary cardiologist is not located in your region, your primary veterinarian can perform basic screening, order biomarkers, and consult by telemedicine with a specialist. Many primary practices manage stable Stage B1 and B2 HCM very competently, with specialist input for staging confirmation and complex cases.

Frequently Asked Questions

At what age should HCM screening start in predisposed breeds?

Many breeders screen breeding stock starting around age 1 to 2. For pet cats of predisposed breeds, annual veterinary exam with auscultation is reasonable, with echocardiography added if a murmur, gallop, or arrhythmia is detected, or based on owner-cardiologist preference for proactive surveillance.

Does a heart murmur mean my cat has HCM?

Not necessarily. Many cats have benign flow murmurs, especially when stressed. Murmurs warrant echocardiography to characterize the underlying cause. Conversely, many HCM cats have no audible murmur, which is why screening is not auscultation-dependent.

Can clopidogrel prevent FATE entirely?

No medication prevents FATE entirely. Clopidogrel reduces but does not eliminate thromboembolic risk in Stage B2 and Stage C HCM cats. The FAT-CAT trial established its benefit relative to aspirin, but ongoing thromboembolic events still occur in some treated cats.

Is pimobendan used in feline HCM?

Pimobendan use in HCM is controversial, particularly with significant LVOTO where positive inotropy could worsen obstruction. Some cardiologists use it selectively in non-obstructive cases or in advanced heart failure. The decision rests with the DACVIM-Cardiology.

Should I avoid adopting a Maine Coon or Ragdoll because of HCM risk?

No. These are wonderful breeds and HCM is manageable for most affected cats. The honest preparation includes budgeting for screening, identifying a veterinarian comfortable with feline cardiac care, and learning the warning signs. Many predisposed-breed cats live long, healthy lives.