What is mitral valve disease (MVD) in Cavaliers?

Mitral valve disease (MVD), also called myxomatous mitral valve disease or degenerative mitral valve disease, is a heart condition, and it is the defining, near-universal health issue of the Cavalier King Charles Spaniel. To understand it: the mitral valve is one of the heart's valves, sitting between the left atrium and the left ventricle, and its job is to close properly so that blood flows in one direction through the heart. In MVD, the mitral valve progressively degenerates (the valve tissue thickens and deforms) so that it no longer closes properly, allowing some blood to leak backward (regurgitate) through the valve with each heartbeat. Over time, this leakage means the heart has to work harder and pump more to maintain circulation, which causes the heart (particularly the left side) to enlarge, and, as the disease advances, can eventually lead to congestive heart failure, in which the heart can no longer keep up and fluid backs up (typically into the lungs). What makes MVD so central to the Cavalier is its extraordinarily high prevalence and early onset in the breed: the great majority of Cavaliers develop MVD in their lifetimes, and they develop it far more commonly and at a much younger age than most breeds, sometimes with a heart murmur (the audible sign of the valve leakage) appearing in dogs only a few years old. MVD is progressive, it typically begins silently (a murmur with no symptoms) and progresses over months to years, and while the rate of progression varies (some dogs progress slowly and live for years after a murmur is detected, others faster), it is the leading cause of death in the breed. The good news is that MVD, while incurable, can be monitored and, with appropriate veterinary management, meaningfully managed, so understanding the condition, and having a Cavalier's heart monitored, is central to caring for the breed.

What is a heart murmur, and what do the stages of MVD mean?

A heart murmur is usually the first detectable sign of MVD in a Cavalier, and understanding murmurs and the stages of the disease helps you understand where your dog is in the progression. A heart murmur is an abnormal sound the veterinarian hears through a stethoscope, caused, in MVD, by the turbulent blood flow of the leaking mitral valve; murmurs are graded by loudness (typically on a scale of 1 to 6), and while a murmur indicates valve leakage, its loudness does not perfectly predict severity, so further assessment is used to stage the disease. Veterinary cardiologists commonly stage MVD using a system (the ACVIM classification) with stages roughly as follows: Stage A, dogs at high risk of developing MVD (which includes all Cavaliers, given the breed predisposition) but without any current heart changes; Stage B, dogs that have MVD (a murmur) but no clinical signs of heart failure, subdivided into Stage B1 (a murmur but without significant heart enlargement) and Stage B2 (a murmur with heart enlargement, meaning the heart has begun to change in response to the leakage); Stage C, dogs that have or have had clinical signs of heart failure (congestive heart failure); and Stage D, end-stage heart failure that is difficult to control. This staging matters for management, because the appropriate treatment depends on the stage. Importantly, research has shown that starting a specific heart medication (pimobendan) in dogs at Stage B2 (heart enlargement but before heart failure) can significantly delay the onset of heart failure, which is why identifying when a dog reaches Stage B2, through veterinary assessment including imaging (echocardiogram) or other measures of heart size, is important. So when a murmur is found in a Cavalier, the veterinarian (or a cardiologist) works to stage the disease and monitor its progression, guiding when to start treatment and how to manage the condition, which is why regular monitoring is so important for a Cavalier with MVD.

How is MVD monitored and treated in Cavaliers?

MVD in Cavaliers is managed through a combination of monitoring and, at the appropriate stage, medication, guided by veterinary care and, often, a veterinary cardiologist. Monitoring: because MVD is progressive, regular monitoring is central to good management. This typically includes regular veterinary check-ups with the vet listening to the heart (to detect a murmur and note changes), and, once a murmur is found, further assessment to stage the disease and track its progression, which may include chest X-rays (to assess heart size and check for fluid in the lungs), an echocardiogram (an ultrasound of the heart, often done by a cardiologist, which is the best way to assess the valve and heart size), and sometimes other tests. The frequency of monitoring increases as the disease progresses. Treatment: MVD cannot be cured, but medication plays an important role at the appropriate stages. A key point, supported by research, is that starting the medication pimobendan when a dog reaches Stage B2 (heart enlargement but before heart failure) can significantly delay the onset of congestive heart failure, meaningfully extending the symptom-free period, which is why monitoring to identify Stage B2 is valuable. Once a dog develops congestive heart failure (Stage C), treatment typically involves a combination of medications (which may include pimobendan, a diuretic such as furosemide to remove excess fluid, and others) to manage the heart failure, control symptoms, and maintain quality of life, and dogs can often live comfortably for a meaningful time with well-managed heart failure. Management is tailored to the individual dog and stage and guided by the veterinarian or cardiologist. For a Cavalier owner, the practical approach is: have the dog's heart monitored regularly (routine check-ups, and cardiology assessment as advised, especially once a murmur is found), follow the veterinary guidance on staging and when to start and adjust medication, watch for signs of heart failure (see the next question), and be prepared for the ongoing veterinary care (and cost) that managing MVD involves, another reason pet insurance is so valuable for the breed.

What are the signs of heart failure to watch for in a Cavalier?

Recognizing the signs of congestive heart failure in a Cavalier with MVD is important, because prompt veterinary attention when heart failure develops or worsens is essential to managing it and maintaining the dog's quality of life. In the earlier stages of MVD, a dog typically has no symptoms (just a murmur), but as the disease advances toward and into heart failure, signs to watch for include: coughing (a common early sign, often a persistent cough, which can be worse at night or after lying down or with activity); increased breathing rate or effort, and difficulty breathing (an important sign, monitoring the dog's resting/sleeping breathing rate at home, the number of breaths per minute while the dog is resting or asleep, is a useful tool, as an increase can be an early sign of fluid building up in the lungs, and your vet can advise on what rate to watch for); reduced exercise tolerance and tiring more easily; lethargy, weakness, or reduced activity; restlessness or difficulty settling, especially at night; a reduced appetite; fainting or collapse (which can occur and warrants urgent attention); and, in advanced cases, a distended abdomen or other signs. If a Cavalier with MVD shows these signs, particularly coughing, increased breathing rate or effort, difficulty breathing, or fainting, it should be assessed by a veterinarian promptly, and signs of significant breathing difficulty or collapse should be treated as an emergency requiring immediate veterinary attention. Monitoring the resting breathing rate at home is a genuinely useful, simple tool for owners of dogs with MVD, and your vet can guide you on it. Catching the transition to heart failure, or a worsening of it, promptly allows treatment to be started or adjusted, which is important for the dog's comfort and quality of life. For an owner of a Cavalier with MVD, knowing these signs, monitoring the dog (including the resting breathing rate), and maintaining regular veterinary care are key parts of managing the condition well.

How do I live with and care for a Cavalier with MVD in Montreal?

Living with a Cavalier that has (or will likely develop) MVD is a normal part of owning the breed, and while it is a serious condition, many Cavaliers live good, happy lives for years with well-managed MVD, so the goal is to manage the condition well and maintain the dog's quality of life. Practical aspects of caring for a Cavalier's heart include: maintaining regular veterinary care and heart monitoring (routine check-ups, and cardiology assessment as advised, to stage and track the disease and guide treatment); following the veterinary guidance on medication (giving prescribed medications consistently, and having them adjusted as the disease progresses), remembering the value of starting pimobendan at Stage B2 to delay heart failure; monitoring the dog at home, including watching for signs of heart failure and, once advised, tracking the resting breathing rate; keeping the dog at a healthy weight (excess weight makes the heart work harder, so keeping a Cavalier lean is genuinely helpful for its heart); providing appropriate, moderate exercise (Cavaliers with heart disease can usually still enjoy gentle activity, but should not be over-exerted, and exercise should be adjusted as the disease progresses and per veterinary advice, and, given the breed, exertion in heat should be avoided, relevant in Montreal summers); managing diet as advised (in later stages, a vet may recommend dietary adjustments, such as moderating sodium); and being prepared for the ongoing veterinary care and cost, which is why pet insurance (taken out while the dog is young, before a murmur appears) is so valuable for the breed. It is also worth having a relationship with a veterinarian you trust, and knowing that veterinary cardiology specialists are available (in the Montreal area, through referral) for more complex assessment and management. Emotionally, it helps to understand that MVD is manageable and that many Cavaliers do well for a long time with good care, while also being realistic that it is a progressive, ultimately life-limiting condition. For an owner, the combination of regular monitoring, appropriate treatment, home observation, weight and exercise management, and good veterinary care allows a Cavalier with MVD to live as well and as long as possible, and caring attentively for the breed's heart is one of the most important things a Cavalier owner does.

Cavalier Heart Health & MVD Management in Montreal

The short answer

MVD is a degenerative disease of the heart's mitral valve, which leaks, enlarging the heart and eventually risking congestive heart failure. It affects the great majority of Cavaliers, often young, and is the leading cause of death. It's incurable but manageable. It usually starts as a silent heart murmur and progresses through stages; crucially, starting the medication pimobendan at Stage B2 (heart enlargement, before failure) can significantly delay heart failure, which is why regular heart monitoring (check-ups, and echocardiograms/X-rays as advised) matters. Watch for coughing, increased breathing rate/effort, and reduced exercise tolerance (monitoring the resting breathing rate at home is a useful tool). Keep the dog lean, exercise moderately, follow veterinary guidance, and, given the costs, insure early. Many Cavaliers live well for years with a managed heart.

Browse Adoptable Dogs in Montreal →

A Cavalier King Charles Spaniel having its heart checked at a Montreal veterinary clinic — Regular heart monitoring, well-timed medication, home observation, and weight management let a Cavalier with MVD live well for years.

If you own or are considering a Cavalier, understanding its heart is the single most important thing you can do for the dog. Mitral valve disease is so common in the breed that every Cavalier owner should expect to deal with it, but the outlook is far from bleak: with monitoring, well-timed medication, and good care, many Cavaliers live happy, comfortable lives for years. Here is how to understand and manage it.

What MVD is

The mitral valve sits between the left atrium and left ventricle and should close so blood flows one way. In MVD, the valve progressively degenerates and no longer closes properly, so blood leaks backward with each beat. Over time the heart works harder, enlarges, and, as the disease advances, can reach congestive heart failure (fluid backs up, typically into the lungs). What makes it central to the breed is its extraordinarily high prevalence and early onset, the great majority develop it, far younger than most breeds (murmurs sometimes at only a few years old).

MVD is progressive, typically beginning silently (a murmur with no symptoms) and progressing over months to years (the rate varies, some dogs slowly, some faster), and it's the leading cause of death in the breed. The good news: while incurable, it can be monitored and meaningfully managed. Understanding the condition and having a Cavalier's heart monitored is central to caring for the breed. See our health guide for the breed's full picture.

Murmurs and the stages of MVD

A heart murmur, an abnormal sound from the turbulent flow of the leaking valve, is usually the first detectable sign. Murmurs are graded by loudness (1 to 6), but loudness doesn't perfectly predict severity, so the disease is staged (the ACVIM system): Stage A (at-risk, which includes all Cavaliers, but no changes), Stage B (MVD/murmur but no heart-failure signs), split into B1 (no significant enlargement) and B2 (with heart enlargement), Stage C (has or had heart failure), and Stage D (end-stage, hard to control).

Staging matters because treatment depends on it. Crucially, research shows that starting the medication pimobendan at Stage B2 (heart enlargement, before heart failure) can significantly delay the onset of heart failure, which is why identifying when a dog reaches B2, through veterinary assessment including imaging (echocardiogram) or other measures of heart size, is important. So when a murmur is found, the vet or cardiologist stages the disease and monitors progression, guiding when to start treatment, which is why regular monitoring is so important.

Monitoring and treatment

Monitoring is central: regular check-ups with the vet listening to the heart, and, once a murmur is found, further assessment to stage and track the disease, chest X-rays (heart size, lung fluid), an echocardiogram (heart ultrasound, often by a cardiologist, the best assessment), and sometimes other tests, with monitoring more frequent as the disease progresses. Treatment: incurable, but medication matters, starting pimobendan at Stage B2 significantly delays heart failure, and once heart failure develops (Stage C), a combination of medications (pimobendan, a diuretic like furosemide to remove fluid, and others) manages it and maintains quality of life.

Management is tailored to the dog and stage and guided by the vet or cardiologist, and dogs can often live comfortably for a meaningful time with well-managed heart failure. The practical approach: monitor the heart regularly (check-ups, and cardiology assessment as advised, especially once a murmur is found), follow the guidance on staging and medication, watch for heart-failure signs (below), and be prepared for the ongoing care and cost, another reason pet insurance is so valuable for the breed. Veterinary cardiology specialists are available in the Montreal area through referral for more complex assessment.

Signs of heart failure to watch for

Earlier MVD is symptomless (just a murmur), but as it advances toward heart failure, watch for: coughing (a common early sign, often persistent, worse at night or with activity), increased breathing rate or effort and difficulty breathing (an important sign, an increase can mean fluid in the lungs), reduced exercise tolerance and tiring easily, lethargy or weakness, restlessness or difficulty settling (especially at night), reduced appetite, and fainting or collapse. A genuinely useful home tool is monitoring the resting/sleeping breathing rate (breaths per minute while resting), your vet can advise what rate to watch for, as an increase can be an early sign.

If a Cavalier with MVD shows these signs, particularly coughing, increased breathing rate or effort, difficulty breathing, or fainting, have it assessed promptly, and treat significant breathing difficulty or collapse as an emergency requiring immediate veterinary attention. Catching the transition to heart failure (or a worsening) promptly lets treatment be started or adjusted, which is important for the dog's comfort and quality of life. Monitoring the resting breathing rate is a simple, valuable tool.

Living with a Cavalier's heart in Montreal

Many Cavaliers live good, happy lives for years with well-managed MVD. Care involves: regular vet care and heart monitoring, consistent medication as prescribed (and the value of pimobendan at Stage B2), home monitoring (including the resting breathing rate once advised), keeping the dog lean (excess weight makes the heart work harder), moderate exercise (gentle activity is usually fine, but avoid over-exertion, adjust as the disease progresses, and avoid exertion in heat, relevant in Montreal summers), diet as advised (later stages may involve moderating sodium), and being prepared for the ongoing care and cost.

It helps to have a veterinarian you trust and to know that veterinary cardiology specialists are available in the Montreal area through referral. Emotionally, it helps to understand that MVD is manageable and many Cavaliers do well for a long time with good care, while being realistic that it's a progressive, ultimately life-limiting condition. The combination of monitoring, appropriate treatment, home observation, and weight and exercise management lets a Cavalier with MVD live as well and as long as possible, caring attentively for the breed's heart is one of the most important things a Cavalier owner does. And because the care can be expensive, pet insurance taken out while the dog is young (before a murmur appears) is genuinely valuable. See our adoption guide.

Browse adoptable dogs in Montreal

With good heart care, an adopted Cavalier makes a devoted, gentle companion for years. Refreshed regularly across Montreal-area organizations.

See Available Dogs →

Frequently Asked Questions

What is MVD?

A degenerative disease of the heart's mitral valve, which leaks, making the heart work harder, enlarge, and eventually risk congestive heart failure. It affects the great majority of Cavaliers, far younger than most breeds, and is the leading cause of death. Incurable but manageable with monitoring and medication.

What is a murmur, and what do the stages mean?

A murmur is the abnormal sound of the leaking valve, usually the first sign. The disease is staged (ACVIM): A (at-risk), B (murmur, no failure; B1 no enlargement, B2 with enlargement), C (has/had heart failure), D (end-stage). Starting pimobendan at B2 significantly delays heart failure, so identifying B2 (via imaging) matters.

How is it monitored and treated?

Monitoring: regular check-ups, and once a murmur is found, chest X-rays, an echocardiogram (often by a cardiologist), and other tests to stage and track it. Treatment: incurable, but pimobendan at Stage B2 delays heart failure, and once failure develops, a combination of medications (pimobendan, a diuretic, others) manages it. Tailored to the dog and stage.

What are the signs of heart failure?

Coughing, increased breathing rate or effort, difficulty breathing, reduced exercise tolerance, lethargy, restlessness at night, reduced appetite, and fainting. Monitoring the resting breathing rate at home is a useful early tool. Have any of these assessed promptly, and treat breathing difficulty or collapse as an emergency.

How do I live with and care for a Cavalier with MVD?

Regular vet care and heart monitoring, consistent medication (and pimobendan at B2), home monitoring (resting breathing rate), keeping the dog lean, moderate exercise (avoiding over-exertion and heat), diet as advised, and being prepared for the cost (insure early). Many Cavaliers live well for years with a managed heart.

Related Montreal guides

Breed Guide

New dog? Start with these care guides

Everything a new adopter needs to set up a safe, happy home.

Dog-proof your home →

The safety sweep before your dog arrives

Traveling with a dog →

Crash-tested car safety and road trips

Exercise & enrichment →

How to tire a dog out, body and brain

Can dogs eat…? →

Which foods are safe, risky, or toxic

What breed is my rescue dog? →

How to figure out a mixed-breed dog

Cavalier Heart Health & MVD Management