Mitral and Tricuspid Regurgitation in Cats: What It Means

Name: Mitral and Tricuspid Regurgitation in Cats: What It Means
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

Mitral regurgitation in cats means the mitral valve on the left side of the heart does not close tightly, so a small amount of blood leaks backward with each beat. This leak creates the murmur your veterinarian hears through the stethoscope. Many cats with mild leakage live normal lives, while others need monitoring or medication depending on how severe the leak is and whether the heart is enlarging.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

A murmur is a sound, not a diagnosis. An echocardiogram (heart ultrasound) shows whether the murmur comes from a leaky mitral valve, a leaky tricuspid valve, or another cause [1].
Mild mitral or tricuspid regurgitation with a normal heart size often needs only regular rechecks, not medication.
Moderate to severe regurgitation that causes chamber enlargement can lead to congestive heart failure over time and may need treatment [2].
Doppler echocardiography is the test that locates the murmur and measures how fast and how turbulent the leaking blood flow is [1].
Any cat with a new murmur, trouble breathing, or open-mouth breathing needs a veterinary visit right away.

What Mitral and Tricuspid Regurgitation Actually Means

Your cat's heart has four chambers. The mitral valve sits between the left atrium and left ventricle, and the tricuspid valve sits between the right atrium and right ventricle. These valves act like one-way doors. When they close properly, blood moves forward only.

When a valve does not seal completely, blood squirts backward through the gap. That backward flow is called regurgitation. The turbulent flow is what your veterinarian hears as a murmur [1].

Mitral valve regurgitation in cats affects the left side of the heart, which handles oxygen-rich blood going to the body. Tricuspid valve regurgitation in cats affects the right side, which handles blood returning from the body to the lungs.

The two problems can occur together. In one reported cat, echocardiography found mild mitral regurgitation along with abnormal tricuspid regurgitation velocities as part of a complex congenital heart problem [3]. That does not mean every cat with one leaky valve has the other, but it does mean a full echo gives a more complete picture than listening alone.

Murmurs and Grades

Veterinarians grade murmurs on a scale of 1 to 6 based on loudness. A grade 1 murmur is barely audible, and a grade 6 murmur is loud enough to be felt through the chest wall. Loudness does not always match severity. A cat can have a loud murmur with mild leakage, or a quiet murmur with a serious problem. That is why the echo matters more than the number your veterinarian writes in the record.

Signs Owners Notice

Many cats with mild valve regurgitation show no signs at all. The murmur is found during a routine exam, and the cat acts completely normal.

When regurgitation becomes significant, the heart works harder to move blood forward. Over time this can cause the affected ventricle to enlarge, a process called volume overload [2]. Signs you might see include:

Sleeping more or tiring faster during play
Hiding more often or seeming less interested in family activity
Faster breathing while resting or sleeping
Coughing, which is less common in cats than in dogs
Open-mouth breathing or breathing with the belly
Reduced appetite or weight loss
Sudden weakness in the back legs, which can signal a blood clot

Breathing rate is one of the most useful things you can track at home. Count breaths while your cat sleeps quietly. A resting rate that climbs over several days is a reason to call your veterinarian.

Some cats with heart disease develop blood clots that travel to the legs or other organs. One report described a cat with hypertrophic cardiomyopathy that developed a clot blocking blood flow to the tongue, causing a swollen, bluish tongue tip along with neurologic signs [4]. Clot risk is a serious concern in cats with certain heart diseases, and your veterinarian will assess that risk for your cat.

Causes and Risk Factors

Valve regurgitation in cats has several possible causes.

Degenerative valve changes. The valve leaflets can thicken or become irregular with age. This is a common cause of valve disease in older pets, and degenerative valve disease of the atrioventricular valves is a recognized cause of volume overload heart failure [2]. Bilateral myxomatous degeneration of the atrioventricular valves has been confirmed on necropsy in at least one cat with complex heart disease [5].

Congenital malformation. Some cats are born with abnormally formed valves. A parachute mitral valve, where the valve structures are malformed, was diagnosed in a young cat during follow-up echocardiograms [3]. These cases often come with other heart defects.

Primary muscle disease. Hypertrophic cardiomyopathy and other muscle diseases can distort the valve apparatus and cause secondary regurgitation. One cat with a hypertrophic cardiomyopathy phenotype had severe left atrial dilation, spontaneous echo contrast, and suspected thrombus formation on echocardiography [4].

Other heart abnormalities. Ventricular septal defects and other shunts change blood flow through the heart and can increase regurgitation. A young cat with a large ventricular septal defect showed severe left heart volume overload, increased pulmonary artery flow, and mild mitral regurgitation [3].

Transient or reversible causes. Some young cats have dynamic changes that improve. A case series described four young cats with systolic anterior motion of the mitral valve and outflow tract obstruction that resolved over time, with normalization of left heart dimensions and successful weaning off diuretics in the cats that had heart failure [6]. Another report described a cat with transient myocardial thickening and congestive heart failure that showed complete reverse remodeling one year later, allowing medical therapy to be discontinued [7]. These cases show that not every heart diagnosis is permanent, which is one reason repeat imaging matters.

Risk factors are not fully established for cats. Age, breed, and underlying heart muscle disease all appear to play a role in individual cases.

How It Is Diagnosed

The first step is a physical exam. Your veterinarian listens for the murmur's location, timing, and grade, checks the pulse, and looks for signs of poor circulation.

Echocardiography is the key test. It is a type of ultrasonography used to evaluate the heart, the aorta, and the pulmonary artery, and it shows the working heart in motion [1]. There are three main types:

2-dimensional echocardiography gives a wedge-shaped video of the heart as it moves [1].
M-mode echocardiography uses a one-dimensional beam to measure chamber size, wall thickness, valve motion, and the size of the aorta and pulmonary artery [1].
Doppler echocardiography detects changing frequencies as the ultrasound beam contacts moving red blood cells, which measures blood flow speed and identifies turbulent or high-speed flow. This is what locates heart murmurs [1].

Together these views let your veterinarian measure chamber dimensions, see valve structure and motion, and calculate pressure differences and blood flow volumes [1]. If you want to understand what the report means in more detail, see Echocardiography in Dogs and Cats: Indications and Basic Interpretation.

Your veterinarian may also recommend chest X-rays to look for heart enlargement and fluid in or around the lungs, blood tests, and a blood pressure check. In cats with suspected hypertrophic cardiomyopathy, additional information is available in Hypertrophic Cardiomyopathy in Cats.

Reading the Severity on an Echo Report

Echo finding	What it usually means	Typical plan
Trace or mild regurgitation, normal chamber size	Small leak, heart not stressed	Recheck exam and echo in 6 to 12 months
Mild regurgitation with mild enlargement	Leak is starting to affect the heart	Recheck in 3 to 6 months, track breathing rate at home
Moderate regurgitation with chamber enlargement	Heart is working harder, heart failure risk rises	Closer monitoring, possible medication, recheck in 1 to 3 months
Severe regurgitation with marked enlargement or heart failure signs	Significant volume overload, possible fluid buildup	Medication and frequent rechecks, sometimes emergency care

Severity on color Doppler is often described by comparing the regurgitant jet area with the size of the receiving chamber. In a study of small-breed dogs with mitral regurgitation murmurs, cases were divided into mild, moderate, and severe groups based on the jet area signal to left atrium ratio, and dogs were also grouped by whether the heart was enlarged and whether clinical signs were present [8]. Cats are not dogs, and feline disease behaves differently, but the principle is similar. Your veterinarian looks at the leak, the heart size, and the cat's signs together.

Treatment Options

Treatment depends on whether the regurgitation is causing heart enlargement or clinical signs.

Monitoring only. Cats with mild regurgitation and a normal heart size often need no medication. The plan is regular exams, periodic echocardiography, and home breathing checks.

Medication for heart failure. When regurgitation causes volume overload and congestive heart failure, treatment aims to remove excess fluid and reduce the heart's workload. A cat with left-sided congestive heart failure was treated with furosemide, clopidogrel, and ondansetron [7]. Your veterinarian calculates each dose from your cat's weight, kidney values, and current health, and adjusts over time.

Clot prevention. Cats with certain heart diseases face a risk of blood clots. Clopidogrel is an antiplatelet medication used in some of these cases [7]. Whether your cat needs it depends on the specific diagnosis and the size of the left atrium. More detail is available in Hypertrophic Cardiomyopathy HCM in Cats: Screening, Clot Prevention and Care.

Rate control and other drugs. Atenolol was prescribed to four young cats with outflow tract obstruction and systolic anterior motion of the mitral valve, and all remained on it through their final recheck [6]. Beta blockers slow the heart rate and can reduce dynamic obstruction in selected cats.

Treating the underlying cause. If hyperthyroidism, anemia, or another condition is driving the heart problem, treating that condition matters. Volume overload can result from high-output states such as hyperthyroidism or anemia [2].

Procedures. Some congenital defects need surgical or interventional treatment. One cat with a ventricular septal defect underwent pulmonary artery banding as palliative treatment [3]. These options are limited to specialized centers and specific defects.

Diuretic withdrawal. In some cats whose heart changes reverse, medication can be reduced or stopped. The cats in one case series that originally had heart failure were successfully weaned off diuretics [6], and another cat had medical therapy discontinued after complete reverse remodeling [7]. Never stop a heart medication on your own. This decision requires repeat imaging and a veterinarian's guidance.

Recovery, Outlook, and Long-Term Management

The outlook varies widely. Mild regurgitation with a normal heart size often stays stable for years. Moderate to severe regurgitation with chamber enlargement carries a higher risk of congestive heart failure over time.

Some cats improve dramatically. The four young cats with dynamic outflow obstruction and systolic anterior motion of the mitral valve had resolution of the obstruction, normalization of left heart dimensions, and no documented recurrence of progressive heart disease or heart failure [6]. A cat with transient myocardial thickening and heart failure showed complete reverse remodeling with normalized left ventricle and left atrial size one year later [7]. These are encouraging examples, though not every cat follows the same path.

Long-term management usually includes:

Recheck exams and echocardiograms at intervals your veterinarian sets
Home resting breathing rate recorded a few times a week
Weight and appetite tracking
Blood work to monitor kidney function and medication effects
Prompt attention to any new breathing change

If your cat has fluid accumulation around the lungs or in the chest, monitoring for recurrence is part of ongoing care. See Monitoring Effusion Recurrence and Management in Dogs and Cats for how effusion is tracked over time.

Prevention

There is no proven way to prevent valve regurgitation in cats. Most cases are related to age, genetics, or congenital structure, and those factors are not something you can control.

What you can do is catch problems early. Keep routine wellness visits, especially as your cat gets older. Mention any change in activity, appetite, or breathing, even if it seems small. If your cat has been diagnosed with a murmur, keep the recheck appointments your veterinarian recommends. Early detection gives you more options and more time.

Limitations and When to Contact a Veterinarian

This article cannot tell you how serious your cat's specific murmur is. Only an examination and usually an echocardiogram can do that. Individual cases need a veterinarian who can see your cat, review the images, and set a plan.

Contact an emergency clinic now if your cat:

Breathes with an open mouth or visibly uses the belly to breathe
Collapses, faints, or cannot stand
Has sudden weakness or paralysis in the back legs, which can indicate a clot
Has a bluish tint to the tongue or gums
Breathes very fast while resting and does not settle

Call for a same-day visit if your cat:

Has a new or louder murmur found at a visit
Shows a resting breathing rate that has climbed over several days
Is coughing, hiding more, or eating less than usual
Has been diagnosed with heart disease and seems worse than last week

Schedule a routine visit if your cat:

Has a known murmur and is due for a recheck
Has mild regurgitation and no signs, with a recheck interval your veterinarian set
Needs blood work to monitor heart medication

Frequently Asked Questions

Does a heart murmur mean my cat has mitral regurgitation?

Not necessarily. A murmur is a sound caused by turbulent blood flow, and an echocardiogram is what identifies the source [1]. Many murmurs in cats come from other causes, including outflow tract obstruction or heart muscle disease. Doppler echocardiography is the test that locates the murmur and shows whether a leaky valve is responsible [1].

Can mild mitral regurgitation in cats get worse over time?

It can, but it does not always. Some cats stay stable for years, and some young cats with dynamic valve changes improve and normalize [6]. Repeat echocardiograms are how your veterinarian tracks whether the leak and heart size are changing. That is why recheck intervals matter even when your cat seems fine.

Will my cat need medication for a leaky heart valve?

Only if the regurgitation is causing heart enlargement or clinical signs. Cats with mild leakage and a normal heart size often need monitoring alone. When congestive heart failure develops, medications such as furosemide and clopidogrel may be used, with doses set by your veterinarian based on your cat's weight and health [7].

Is tricuspid regurgitation in cats more serious than mitral regurgitation?

It depends on the cause and how much the heart is affected, not on which valve is involved. Tricuspid regurgitation affects the right side of the heart, and mitral regurgitation affects the left side. Both can be mild and stable or part of a complex problem, and some cats have both at once [3]. The echocardiogram and your cat's signs determine the seriousness.

How often should my cat's heart be rechecked?

Your veterinarian sets the interval based on severity, heart size, and whether your cat has signs. Mild cases with a normal heart size are often rechecked every 6 to 12 months, while moderate or severe cases may need rechecks every 1 to 3 months. Home breathing rate checks between visits help you know if something is changing sooner.

References

Diagnosis of Cardiovascular Disease in Cats - Cat Owners. Merck Veterinary Manual.
Heart Failure in Cats - Cat Owners. Merck Veterinary Manual.
Cardiovascular images: parachute mitral valve in a cat. Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology, 2025.
Tongue infarction in suspected lingual artery thromboembolism in a cat with hypertrophic cardiomyopathy. JFMS open reports, 2026.
Concurrent Persistent Truncus Arteriosus and Left Atrial Diverticulum in a Domestic Short-Haired Cat. Animals : an open access journal from MDPI, 2025.
Resolution of dynamic left ventricular outflow tract obstruction and reversible left ventricular hypertrophy in 4 cats. The Canadian veterinary journal = La revue veterinaire canadienne, 2024.
Recurrent transient myocardial thickening and congestive heart failure in a cat. Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology, 2026.
Echocardiographic Findings in Small-Breed Dogs With Myxomatous Mitral Valve Disease and the Severity of Mitral Regurgitation, Heart Size and Clinical Signs Myxomatous Mitral Valve Disease in Dogs. Veterinary medicine and science, 2026.