What is the most common type of cardiomyopathy in cats?

Hypertrophic cardiomyopathy (HCM) is by far the most common — it accounts for approximately 65–70% of feline cardiomyopathy cases. In HCM, the left ventricular wall thickens abnormally, reducing the volume available for blood filling and impairing diastolic function (the heart's ability to relax and fill). HCM is genetic in Maine Coons and Ragdolls, and spontaneous in many other cats including mixed breeds.

What is restrictive cardiomyopathy (RCM) in cats?

Restrictive cardiomyopathy (RCM) is the second most common form, accounting for roughly 15% of cases. Fibrous scar tissue forms inside the heart (endocardial fibrosis), making the walls stiff and preventing normal filling. The heart contracts normally but cannot relax and fill adequately. RCM tends to affect older cats, is not associated with known genetic mutations, and generally carries a worse prognosis than HCM. Left atrial enlargement is usually marked, making saddle thrombus risk high.

What is dilated cardiomyopathy (DCM) in cats?

Dilated cardiomyopathy (DCM) in cats is rare today — it was once far more common until the discovery that taurine deficiency was the primary cause. Since commercial cat food manufacturers added taurine to their products in the late 1980s, feline DCM became uncommon. Today it should be suspected in cats eating unusual homemade, vegan, or exotic protein diets that may lack adequate taurine. Unlike HCM (thick walls) or RCM (stiff walls), DCM features thin, dilated, weakly contracting walls — similar to canine DCM.

What is unclassified cardiomyopathy (UCM) in cats?

Unclassified cardiomyopathy (UCM) is diagnosed when echocardiographic findings don't cleanly fit HCM, RCM, or DCM criteria. It may represent overlap between types or an intermediate stage. Some cats classified as UCM are later reclassified as their disease progresses. Management is similar to other forms — based on the predominant functional abnormality and clinical signs.

How is cardiomyopathy diagnosed in cats?

Echocardiogram is the gold standard — it distinguishes HCM (thick walls), RCM (fibrous tissue, large left atrium), and DCM (dilated, thin, weak walls). A cardiac auscultation finding of murmur, gallop, or arrhythmia prompts workup. NT-proBNP blood test screens for significant heart disease. Chest X-rays detect pleural effusion and cardiomegaly. T4 testing rules out hyperthyroidism-induced cardiac changes. Blood pressure identifies hypertension. Note: many cats with significant HCM have no audible murmur.

Can cardiomyopathy in cats be treated?

Most feline cardiomyopathy is managed but not cured. Treatment depends on type and stage. For HCM, atenolol or diltiazem may improve diastolic filling. Furosemide manages fluid accumulation in CHF. Clopidogrel reduces thromboembolism risk in cats with left atrial enlargement. For DCM with confirmed taurine deficiency, taurine supplementation and diet change can produce partial or full recovery — the only potentially reversible form. RCM and UCM are managed similarly to HCM once CHF develops.

Which cat breeds are most at risk for cardiomyopathy?

Maine Coons and Ragdolls have a known MYBPC3 genetic mutation causing HCM — genetic testing is available. Other breeds at elevated risk include Persians, British Shorthairs, Sphynx, Scottish Folds, and American Shorthairs. Mixed-breed cats can develop HCM spontaneously. HCM is the most common heart disease in all cats, not just pedigree breeds. Middle-aged to older males are at higher risk overall.

Cardiomyopathy in Cats: HCM, RCM, DCM Types, Symptoms & Treatment (2026)

Q: What is cardiomyopathy in cats?

Cardiomyopathy is disease of the heart muscle itself, as opposed to valve disease or pericardial disease. It is the most common form of heart disease in cats, affecting an estimated 10–15% of the feline population. There are four main types: hypertrophic cardiomyopathy (HCM), restrictive cardiomyopathy (RCM), dilated cardiomyopathy (DCM), and unclassified cardiomyopathy (UCM). HCM accounts for roughly 65–70% of feline cardiomyopathy cases.

Q: What is the prognosis for cats with cardiomyopathy?

Prognosis varies widely by type and severity. Many cats with mild HCM live normal lifespans with minimal intervention. Cats who develop CHF (pleural effusion or pulmonary edema) have a median survival of 3–18 months with treatment. RCM carries a worse prognosis than HCM due to more severe left atrial enlargement and higher thromboembolism risk. DCM due to taurine deficiency is the most treatable — some cats fully recover. Left atrial size is the single best predictor of near-term risk.

Feline Cardiomyopathy: Quick Facts

• Prevalence: Affects ~10–15% of all cats; most common feline heart disease
• Most common type: HCM (~65–70% of cases) — thick walls, impaired filling
• Second most common: RCM (~15%) — scarred walls, poor relaxation, worse prognosis
• Reversible type: DCM from taurine deficiency — treatable with diet + supplementation
• Cats hide illness: Most are asymptomatic until acute respiratory crisis
• Diagnosed by: Echocardiogram — the only way to distinguish the four types

Managing a cat with cardiomyopathy?

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Is My Cat's Heart Disease Serious?

Cardiomyopathy is not one disease — it is four distinct conditions that look different on echocardiogram, progress differently, and respond to different treatments. Knowing which type your cat has changes everything about prognosis, medication choices, and what to monitor.

The Four Types of Feline Cardiomyopathy

HCM

~65–70%

What happens: Left ventricular wall thickens; diastolic dysfunction (poor filling)

Notes: Worse with small chamber; left atrial size predicts CHF risk

RCM

~15%

What happens: Fibrous scar tissue inside heart; walls stiffen; poor relaxation

Notes: Often worse than HCM; large LA common; high thrombus risk

DCM

Rare (<5%)

What happens: Walls dilate and thin; systolic dysfunction (poor pumping)

Notes: Best prognosis if taurine-related; potentially reversible

UCM

~10–15%

What happens: Mixed features not fitting other categories

Notes: Managed based on dominant functional abnormality

Type	Frequency	What Happens in the Heart	Key Notes
HCM	~65–70%	LV wall thickens; diastolic dysfunction (poor filling)	Left atrial size is the key prognostic marker
RCM	~15%	Fibrous scar tissue stiffens walls; poor relaxation	Often worse prognosis; high thrombus risk
DCM	Rare (<5%)	Chambers dilate and thin; systolic dysfunction	Often taurine deficiency — potentially reversible
UCM	~10–15%	Mixed features not fitting other categories	Managed by dominant functional abnormality

HCM: The Most Common Type

Hypertrophic cardiomyopathy is the form most people mean when they say a cat has cardiomyopathy. The left ventricular wall thickens abnormally — often to more than twice its normal thickness — leaving a smaller chamber that fills poorly. The heart pumps hard but cannot hold enough blood.

The major risk from HCM is not immediate pump failure but the long-term consequences of elevated filling pressures — fluid backing up into or around the lungs (congestive heart failure) and blood clots forming in the enlarged, sluggish left atrium (saddle thrombus).

HCM has a known genetic mutation (MYBPC3) in Maine Coons and Ragdolls, making genetic testing possible. In all other cats, including mixed breeds, it is presumed to have a genetic basis but no test is currently available. For a full deep-dive into HCM specifically, see our dedicated HCM article.

RCM: The Often-Overlooked Type

Restrictive cardiomyopathy is the second most common and often the least well-understood. Fibrous scar tissue — endocardial fibrosis — forms on the inner surface of the heart, making the walls stiff and preventing normal relaxation and filling. Unlike HCM (thick walls) or DCM (thin walls), the walls in RCM may appear normal in thickness but are lined with fibrosis that echocardiogram can detect.

RCM typically presents in older cats, has no known genetic mutation, and is generally harder to manage than HCM. Left atrial enlargement tends to be more severe, making saddle thrombus risk particularly high. Some cardiologists argue the prognosis for RCM is worse than for HCM — median survival after CHF diagnosis tends to be on the shorter end of the range.

RCM vs. HCM on echocardiogram

HCM: thick LV walls (>6mm), small or normal LA initially. RCM: normal or mildly thick walls with severely enlarged LA and biatrial enlargement, plus visible endocardial fibrosis. The combination of marked LA enlargement with relatively normal wall thickness should raise suspicion for RCM over HCM.

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DCM: Rare but Potentially Reversible

Dilated cardiomyopathy in cats was historically common until the 1990s, when researchers discovered it was caused by dietary taurine deficiency. After commercial cat food manufacturers added taurine supplementation, feline DCM became rare. Today, DCM should be suspected in cats eating:

• Homemade diets not formulated for cats
• Vegan or vegetarian cat diets
• Exotic protein diets with unusual ingredients
• Dog food (taurine-poor compared to cat requirements)

Unlike all other cardiomyopathy types, taurine-deficient DCM is potentially reversible. Cats started on taurine supplementation (250–500 mg twice daily) and transitioned to a complete and balanced commercial cat food sometimes show partial or full cardiac recovery over weeks to months — making measurement of taurine levels essential in any cat with DCM features on echo.

Symptoms: What to Look For

Cats are expert at hiding illness. Most cardiomyopathy is asymptomatic until a crisis develops. When symptoms do appear:

• Rapid or labored breathing — resting respiratory rate above 30 breaths/minute is the most reliable early warning sign
• Open-mouth breathing — always abnormal in cats; indicates severe respiratory compromise
• Lethargy and hiding — seeking solitude, less active than usual, not greeting owners
• Reduced appetite — often the first subtle sign owners notice
• Sudden hind limb paralysis — saddle thrombus; screaming in pain, cold rear legs, pale/blue footpads
• Abdominal breathing effort — belly moving visibly with each breath (abdominal splinting)

Cats don't cough with cardiomyopathy

Unlike dogs, cats almost never cough when their heart is failing. A coughing cat is far more likely to have asthma or bronchitis. The hallmark of feline cardiac disease is fast, quiet, labored breathing — not coughing.

Causes and Risk Factors

Genetic Mutation (HCM)

MYBPC3 mutation in Maine Coons and Ragdolls is the only identified feline cardiac gene. Genetic testing available for these two breeds. All other cats with HCM are presumed to have uncharacterized genetic variants.

Taurine Deficiency (DCM)

Inadequate taurine in the diet causes DCM. Cats are obligate carnivores and cannot synthesize taurine — it must come from food. Measure taurine levels in any cat with DCM features or on an unusual diet.

Hyperthyroidism (Secondary)

Untreated hyperthyroidism causes secondary HCM-like changes. These can partially reverse with thyroid treatment. T4 must be measured in every cat with cardiomyopathy.

Hypertension (Secondary)

Systemic hypertension forces the heart to work harder, causing secondary wall thickening mimicking HCM. Blood pressure measurement is essential — treatment with amlodipine may improve cardiac findings.

Idiopathic (RCM, UCM)

No cause has been identified for RCM or most UCM cases. They are presumed to have genetic or inflammatory origins that are not yet characterized. Management is symptomatic.

Diagnosis

Echocardiogram — Essential to distinguish the four types. Measures wall thickness, chamber dimensions, LA:Ao ratio, systolic function, and identifies endocardial fibrosis. Should ideally be performed by a veterinary cardiologist.

Chest X-rays — Detects pleural effusion (most common CHF presentation in cats), cardiomegaly, and pulmonary edema. Essential at presentation and for monitoring.

NT-proBNP blood test — Elevated with significant heart disease. Useful screening test, especially when exam is inconclusive or to differentiate cardiac from respiratory causes of breathing difficulty.

T4 (thyroid hormone) — Rules out hyperthyroidism-induced cardiac changes in any middle-aged or senior cat. Must be measured before attributing changes to primary cardiomyopathy.

Blood pressure — Identifies hypertension, which may cause or worsen cardiac changes. Treated separately with amlodipine.

Taurine levels — Whole blood taurine should be measured in any cat with DCM features or on a diet that may lack taurine. A potentially life-changing test if low.

Treatment by Type

HCM

Atenolol or diltiazem to slow heart rate + improve filling; furosemide if CHF develops; clopidogrel if LA enlarged

RCM

Similar to HCM — furosemide for CHF, clopidogrel for thrombus prevention. Often requires higher diuretic doses due to severe LA enlargement.

DCM (taurine deficiency)

Taurine 250–500 mg twice daily + transition to complete commercial cat food. May partially or fully recover over weeks to months. Also furosemide if CHF present.

UCM

Managed based on dominant functional abnormality — diastolic or systolic dysfunction. Supportive care and CHF management as needed.

Type	Primary Treatment Approach
HCM	Atenolol or diltiazem (heart rate control); furosemide when CHF develops; clopidogrel for LA enlargement; thoracocentesis for pleural effusion
RCM	Similar to HCM; higher diuretic doses often needed; clopidogrel important due to severe LA enlargement; guarded prognosis
DCM (taurine deficiency)	Taurine 250–500 mg twice daily + diet change to complete commercial cat food; furosemide if CHF; partial or full cardiac recovery possible
UCM	Treat dominant functional abnormality; supportive CHF management; prognosis variable

Breed Predispositions

• Maine Coon — MYBPC3 mutation; genetic test available; cardiologist echo screening from age 2 recommended
• Ragdoll — Separate MYBPC3 mutation; genetic test available; may develop HCM at a younger age than Maine Coons
• Persian — Elevated HCM risk; no genetic test available; annual cardiac screening recommended
• British Shorthair — High HCM prevalence; breeding cats should be screened
• Sphynx — HCM and RCM both reported; among the highest HCM prevalence of any breed
• Scottish Fold — Cardiomyopathy in context of osteochondrodysplasia; all Folds should be screened
• Domestic shorthair / mixed breed — HCM is common even without breed predisposition; all middle-aged and senior cats benefit from regular cardiac auscultation

Key Takeaway

The type of cardiomyopathy matters — HCM, RCM, DCM, and UCM have different causes, different prognoses, and different treatment priorities. An echocardiogram is the only way to know which type your cat has.

The one universal truth: cats hide cardiac disease until they crash. Learn your cat's normal resting respiratory rate now. Count breaths for 30 seconds while sleeping, double it. Above 30 per minute consistently — call your vet that day.

Echocardiograms, cardiologist visits, and lifelong cardiac medications — pet insurance helps

Managing feline cardiomyopathy means repeat echocardiograms ($300–500 each), specialist cardiology visits, ongoing medications (atenolol, clopidogrel, furosemide), and emergency care for CHF events. Pet insurance can significantly offset these costs — ideally started before a formal diagnosis.

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✓ How left atrial size and wall thickness have changed
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Is My Cat's Cardiomyopathy Getting Worse?

Frequently Asked Questions

What is cardiomyopathy in cats?

Disease of the heart muscle. The four types are HCM (thickened walls, ~65% of cases), RCM (scarred stiff walls, ~15%), DCM (dilated thin walls, rare), and UCM (mixed/unclassified). An echocardiogram is required to tell them apart — clinical signs are similar across all types.

What's the difference between HCM and RCM in cats?

HCM: walls are abnormally thick, reducing filling volume. RCM: walls are normal thickness but lined with fibrous scar tissue, making them stiff. Both impair diastolic function but via different mechanisms. RCM generally carries a worse prognosis and involves more severe left atrial enlargement.

Can feline DCM be reversed?

Yes — if caused by taurine deficiency. Taurine supplementation (250–500 mg twice daily) and transition to a complete commercial cat food can produce partial or full cardiac recovery in weeks to months. This makes taurine measurement essential in any cat presenting with DCM features.

How do I know if my cat has cardiomyopathy?

Most cats show no signs until crisis. Your vet may detect a murmur, gallop rhythm, or arrhythmia during a routine exam — though many cats with significant HCM have no murmur. NT-proBNP blood testing screens for significant heart disease. Echocardiogram definitively diagnoses and types the cardiomyopathy.

What is the prognosis for cats with cardiomyopathy?

Highly variable. Mild HCM with no CHF: normal lifespan possible. HCM or RCM with CHF: median survival 3–18 months with treatment. DCM from taurine deficiency: best prognosis, partial/full recovery possible. Left atrial size on echocardiogram is the single most important prognostic indicator.

Does cardiomyopathy cause coughing in cats?

No — cats almost never cough with cardiomyopathy. Coughing in cats strongly suggests asthma or bronchitis. Cardiac disease in cats presents as fast or labored breathing, open-mouth breathing, lethargy, and reduced appetite — not coughing.

Should I get a genetic test for my Maine Coon or Ragdoll?

Yes — genetic testing for the MYBPC3 mutation is available for Maine Coons and Ragdolls. A negative result reduces but does not eliminate risk, as other mutations may exist. Annual echocardiogram screening by a cardiologist from age 2 remains the most reliable way to detect HCM early in these breeds.

Cardiomyopathy in Cats: HCM, RCM, DCM Types, Symptoms & Treatment