Heart disease in senior dogs: types, symptoms, and treatment

You notice it first in small ways. Your dog pauses halfway up the stairs he used to bound up. He coughs at night, a soft, almost apologetic sound that wakes you before it wakes him. He tires on walks that used to be nothing. At his last checkup, the vet paused a little longer with the stethoscope, listened again, and said the word that made your stomach drop: murmur. Maybe then, or maybe months later, you heard the fuller phrase: heart disease.

Canine heart disease is one of the most common serious illnesses of aging dogs. Studies suggest that roughly 10 percent of all dogs develop some form of cardiac disease in their lifetime, and the number rises sharply with age. By age 10, as many as a third of small-breed dogs show evidence of mitral valve disease, and certain large breeds face their own significant risk of cardiomyopathy. For many owners, the diagnosis feels like a countdown. It does not have to be. With early detection and modern medication, many dogs live comfortable, happy years after their diagnosis.

This guide explains what heart disease in dogs actually is, the two most common forms, the signs to watch for, how veterinarians stage and diagnose it, and the full range of treatments and home changes that can make a real difference. The goal is to help you understand what is happening inside your dog's chest, so you can advocate for the care that gives him the most good days possible.

What heart disease in dogs actually is

Your dog's heart is a four-chambered muscular pump about the size of his clenched paw. It has two atria (upper chambers) that receive blood and two ventricles (lower chambers) that pump it out. Between each atrium and ventricle is a one-way valve, and larger valves sit where the ventricles empty into the great arteries. Specialized electrical tissue sets the rhythm, and the whole structure is fed by its own set of small coronary arteries. When everything is working, the heart moves between 60 and 160 beats per minute in a dog, quietly delivering oxygen to every cell in the body.

Heart disease is any condition that interferes with this machinery. The term covers a wide range of problems: leaky or thickened valves, weakened or stiffened heart muscle, abnormal electrical rhythms, congenital defects, and fluid collecting around the heart. In senior dogs, the two dominant forms are mitral valve disease (also called myxomatous mitral valve disease or degenerative valve disease) and dilated cardiomyopathy (DCM). Together, these account for the large majority of acquired heart disease in dogs over age 7.

It is important to understand the difference between heart disease and heart failure. Heart disease is the presence of a structural or functional problem with the heart. Heart failure is the clinical syndrome that occurs when the heart can no longer meet the body's demands, and fluid starts to back up into the lungs or the abdomen. Many dogs live for years with heart disease before ever developing heart failure, and modern medicine has gotten remarkably good at delaying that progression.

Mitral valve disease: the most common form

Mitral valve disease, often called MVD or myxomatous mitral valve disease (MMVD), is by far the most common heart disease in dogs. It accounts for roughly 75 percent of all canine cardiac cases. It primarily affects small and medium breeds, especially Cavalier King Charles Spaniels, Chihuahuas, Miniature Poodles, Dachshunds, Shih Tzus, Yorkies, Maltese, and Miniature Schnauzers, though it can appear in any breed.

The mitral valve sits between the left atrium and left ventricle. In a healthy dog, it snaps shut with each heartbeat to prevent blood from flowing backward. In MVD, the valve leaflets gradually thicken and become lumpy, and they no longer close properly. Each time the ventricle contracts, a small amount of blood leaks backward into the atrium. This backward flow is what creates the characteristic murmur your vet hears. At first, the leak is minor and the heart compensates easily. Over time, the atrium stretches to hold the extra blood, the ventricle works harder, and eventually the system can no longer keep up. Fluid begins to accumulate in the lungs, and congestive heart failure develops.

The progression of MVD is usually slow, measured in years rather than months. Many dogs are diagnosed with a murmur at a routine checkup and live several more years before any symptoms appear. Cavalier King Charles Spaniels are a notable exception: the breed has an unusually early onset, with many dogs developing murmurs before age 5 and progressing more rapidly than other breeds.

Dilated cardiomyopathy: the large-breed heart disease

Dilated cardiomyopathy, or DCM, is a disease of the heart muscle itself rather than the valves. In DCM, the heart muscle becomes thin, weak, and stretched, and the chambers enlarge. The heart still fills with blood, but it cannot contract strongly enough to pump it out efficiently. Blood backs up, the chambers dilate further, and eventually congestive heart failure develops. DCM often also causes irregular heart rhythms, and some dogs die suddenly from these arrhythmias before outward symptoms appear.

DCM primarily affects large and giant breeds, especially Doberman Pinschers, Boxers, Great Danes, Irish Wolfhounds, Saint Bernards, and Newfoundlands. Dobermans are particularly predisposed, with some studies showing that nearly 60 percent develop DCM in their lifetime. Cocker Spaniels are the notable medium-sized exception. Unlike MVD, DCM often progresses faster once symptoms appear, and a subset of dogs experience sudden death from arrhythmia without warning.

In recent years, veterinarians have recognized a subset of DCM linked to diet, particularly grain-free and boutique or exotic-ingredient foods rich in peas, lentils, and other legumes. The FDA has studied this association since 2018. Unlike genetic DCM, diet-associated DCM can sometimes improve significantly when the food is changed, making an accurate diagnosis and a careful diet review important for any newly diagnosed dog.

Other causes of heart disease in senior dogs

Beyond MVD and DCM, several other conditions can affect the aging canine heart:

Arrhythmias. Abnormal heart rhythms, including atrial fibrillation, ventricular arrhythmias, and slow sinus rhythms, become more common with age and can occur with or without underlying structural disease.

Pericardial effusion. Fluid can accumulate in the sac surrounding the heart, squeezing it and preventing proper filling. In older dogs, this is often caused by a tumor on the heart base or right atrium, most commonly hemangiosarcoma.

Pulmonary hypertension. High pressure in the lung arteries can develop on its own or as a complication of advanced mitral valve disease and makes the right side of the heart work harder.

Heartworm disease. Though preventable, heartworm infection causes progressive damage to the heart and lungs and can look like other cardiac disease on early exam.

Congenital defects. Conditions like patent ductus arteriosus or subaortic stenosis are usually identified young, but in mild cases they can go undiagnosed until the aging heart starts to struggle.

The signs to watch for

Early heart disease often has no outward signs at all. Many dogs are diagnosed only because their vet happens to hear a murmur during a routine visit. But as the disease progresses, most dogs show some combination of the signs below. These symptoms can develop gradually, and because they overlap with other senior conditions, they are easy to miss or write off as simple aging.

Coughing, especially at night

A persistent cough is one of the most common signs of advancing heart disease in dogs. As the left atrium enlarges, it can press on the airway passing above it, triggering a soft, honking cough. When fluid begins to accumulate in the lungs, the cough becomes wetter and more frequent, and it is often worst at night or in the early morning. Any older small-breed dog with a new cough deserves a cardiac workup.

Exercise intolerance

A dog with early heart disease may simply tire more easily. He might slow down on walks, stop to rest on routes he used to breeze through, or refuse to play for as long as he used to. This is often interpreted as normal aging, but when it develops over weeks to months rather than years, it is worth investigating.

Increased breathing rate at rest

A healthy resting dog takes fewer than 30 breaths per minute when relaxed or asleep. A resting respiratory rate consistently above 40 is a strong indicator that fluid is collecting in the lungs. Counting your dog's breaths while he sleeps is one of the most useful things you can do at home to monitor heart disease. Watch his chest rise and fall for 30 seconds and multiply by two. A rising trend over several days can warn you of impending heart failure days before your dog looks visibly sick.

Labored or rapid breathing

As fluid builds up, breathing becomes more visibly effortful. The belly may push harder with each breath, the chest may heave, or your dog may stand with elbows held out from his body to maximize chest expansion. Blue or gray gum color is a true emergency.

Fainting or collapse

Brief episodes of fainting (syncope) can occur when the heart cannot briefly maintain blood flow to the brain, usually triggered by excitement, exercise, or a sudden arrhythmia. The dog typically recovers within seconds. Any episode of collapse in a senior dog should prompt an urgent cardiac evaluation.

Abdominal swelling

Right-sided heart failure causes fluid to back up into the abdomen rather than the lungs. The belly looks bloated, pear-shaped, or fluid-filled. This is more typical of DCM, pericardial disease, and advanced tricuspid valve disease.

Weight loss and muscle wasting

Chronic heart disease has a remarkable ability to waste muscle, a condition called cardiac cachexia. Even if appetite is preserved, the dog's topline, thighs, and shoulders may visibly thin over months.

Restlessness, especially at night

Dogs with worsening heart failure often cannot settle comfortably. They pace, shift positions, or refuse to lie down fully on their sides because lying flat makes breathing harder. A sudden change in sleep patterns in a dog with known heart disease is a warning sign.

How heart disease is diagnosed

Diagnosing and staging heart disease accurately is essential, because treatment depends heavily on which type of disease your dog has and how far it has progressed. A typical cardiac workup includes several of the following steps.

Physical examination and auscultation

The first clue is almost always a heart murmur heard through the stethoscope. Vets grade murmurs from I (very soft) to VI (loud enough to feel through the chest wall). Your vet will also check your dog's gum color, capillary refill time, pulse quality, and listen to the lungs for crackles that suggest fluid.

Chest X-rays

Radiographs show the size and shape of the heart, the position of the major vessels, and whether fluid is present in the lungs. Serial X-rays over time are one of the best ways to monitor progression.

Echocardiogram (cardiac ultrasound)

An echocardiogram is the gold standard for diagnosing heart disease in dogs. It allows a veterinary cardiologist or trained general practitioner to see the heart in motion, measure each chamber, evaluate valve function, and precisely distinguish MVD from DCM and other conditions. For any dog with a new murmur or suspected heart disease, an echo is the single most useful test.

Electrocardiogram (ECG)

An ECG records the electrical activity of the heart and is essential for diagnosing arrhythmias. For dogs with suspected intermittent arrhythmias, a 24-hour Holter monitor can record a full day of heart rhythm at home.

Blood tests

A biomarker called NT-proBNP is released when the heart muscle is stretched. High levels suggest significant cardiac disease and can help distinguish cardiac causes of cough or breathing difficulty from respiratory ones. Routine bloodwork and kidney values are also important, because most cardiac medications affect kidney function and electrolytes.

Blood pressure

Hypertension can worsen heart disease and is worth screening in any senior dog with cardiac concerns.

Staging: the ACVIM classification

Veterinary cardiologists use the American College of Veterinary Internal Medicine (ACVIM) staging system to describe how far heart disease has progressed. Understanding your dog's stage helps you understand his prognosis and treatment.

Stage A: A dog at risk for heart disease (for example, a Cavalier King Charles Spaniel) but with no current evidence of it. No medication is needed; monitoring is key.

Stage B1: A murmur is present, but the heart has not yet enlarged. No medication is typically required, and many dogs stay in this stage for years.

Stage B2: The heart has enlarged on imaging, but the dog still feels fine and has no symptoms of heart failure. This is the stage where starting the medication pimobendan has been shown to significantly delay the onset of heart failure and extend life.

Stage C: Current or past signs of congestive heart failure are present. Multi-drug therapy is required, and most dogs respond well initially.

Stage D: Heart failure that no longer responds to standard therapy. Specialist management, additional medications, and careful quality-of-life discussions become central.

Treatment options

Modern cardiac medicine has transformed what the diagnosis of heart disease means for a dog. Twenty years ago, a diagnosis of congestive heart failure often meant only months of life. Today, with the right combination of drugs, many dogs live comfortably for a year or more past that point, and dogs started on medication earlier in the disease live even longer.

Pimobendan (Vetmedin)

Pimobendan is the single most important advance in canine heart disease in decades. It strengthens the heart's contraction while also dilating blood vessels to reduce the work the heart has to do. In the landmark EPIC study, starting pimobendan in dogs with enlarged hearts from mitral valve disease (Stage B2) delayed the onset of heart failure by roughly 15 months and extended survival significantly. It is now standard of care for both Stage B2 and Stage C disease in most forms of canine heart disease.

Diuretics (furosemide, torsemide)

Diuretics remove excess fluid from the body by signaling the kidneys to produce more urine. Furosemide (Lasix) is the workhorse drug for treating congestive heart failure, and torsemide is a more potent option used when furosemide stops working well. Dogs on diuretics need free access to water, regular kidney-value monitoring, and owners who watch for dehydration.

ACE inhibitors (enalapril, benazepril)

ACE inhibitors reduce the workload on the heart by preventing blood vessels from constricting. They are often combined with pimobendan and diuretics in multi-drug protocols and help preserve kidney function in dogs with chronic heart disease.

Spironolactone

Spironolactone is a mild diuretic that also blocks hormones that drive long-term heart remodeling. It is commonly added to the standard heart failure combination to provide additional support.

Antiarrhythmic medications

Dogs with dangerous irregular rhythms may need drugs like sotalol, mexiletine, or amiodarone. These are chosen based on the type of arrhythmia and usually require ECG-guided adjustment, often in consultation with a cardiologist.

Diet and supplements

For dogs with heart failure, moderate sodium restriction is generally recommended, though extreme low-sodium diets are usually unnecessary. Therapeutic cardiac diets are available through your veterinarian. Supplements with some evidence of benefit include taurine (particularly for breeds with documented deficiencies, like Cockers), L-carnitine, fish oil (omega-3 fatty acids), and CoEnzyme Q10. Any grain-free, boutique, or exotic-ingredient diet should be reviewed with your vet in light of the ongoing FDA investigation into diet-associated DCM.

Procedures and surgery

Pericardial effusion often requires pericardiocentesis, a procedure in which fluid is drained from around the heart. In specialist centers, transcatheter mitral valve repair is now available for select dogs with advanced MVD, offering the possibility of a significant reduction in valve leakage without open-heart surgery. Open-chest mitral valve repair is available at a handful of veterinary centers worldwide and can be life-changing for the right candidate.

Monitoring at home

One of the most important things you can do for a dog with heart disease is track his resting respiratory rate at home. Count his breaths while he is fully asleep and at rest, not while panting or excited. Watch the chest rise and fall for 30 seconds, then double it.

A consistent rate under 30 is normal. A sustained rate above 40, especially if trending upward over several days, often signals fluid building up in the lungs even before your dog looks unwell. Sharing this trend with your vet allows medication adjustments to be made early, which can prevent a hospital visit. Many owners keep a simple chart or phone-app log, and it becomes one of the most valuable tools in managing cardiac disease.

Making your home heart-friendly

Small changes to your dog's daily routine and environment can make a real difference in how comfortable he feels.

Moderate, consistent exercise

Exercise is not forbidden for most dogs with heart disease; it is simply scaled down. Short, gentle walks keep muscle and mental engagement up without overtaxing the heart. Avoid intense play, hot weather, steep hills, and any activity that leaves your dog panting heavily for long periods. Let your dog set the pace. If he wants to stop and sniff, that is fine; the point is to move gently, not to push.

Temperature control

Heat stress is especially hard on a compromised heart. Keep your dog indoors during the hottest part of the day, provide air conditioning or fans, and avoid car travel in summer heat.

Weight management

Extra weight makes the heart work harder. For overweight dogs, safe gradual weight loss can meaningfully reduce cardiac demand, but weight loss must be careful in dogs on diuretics or with cardiac cachexia, since muscle loss is a real risk.

Stress reduction

Sudden excitement, loud noises, and stressful events can trigger fainting in vulnerable dogs. Calm, predictable routines help. Thunderstorm or fireworks anxiety may warrant anti-anxiety medication from your vet.

Elevated food and water

Raising bowls slightly can make eating and drinking less tiring for dogs with breathing difficulty.

Easy access to comfortable rest

Soft, supportive bedding in cool, quiet areas gives your dog a safe place to recover from exertion. Many heart-failure dogs prefer to sleep propped up on a pillow, which makes breathing easier.

What to avoid

• Skipping or doubling medication doses. Heart medications work best when given consistently and at the same time each day. If you miss a dose, do not double up; skip it and resume at the next scheduled dose, and ask your vet if unsure.
• High-salt treats. Jerky, cheese, lunch meat, pretzels, and processed treats load a compromised heart with sodium. Stick to low-sodium options or fresh vegetables your vet approves.
• Strenuous exercise in hot weather. Intense play or long walks in heat or humidity can trigger acute decompensation.
• Over-the-counter cold and flu medications for humans. Many contain decongestants or stimulants that are dangerous for dogs with heart disease.
• Unregulated "heart" supplements. Some marketed supplements contain ingredients that interact with prescription medications. Always check with your vet before adding anything new.
• Ignoring the resting respiratory rate trend. A rising rate is often the earliest sign of worsening heart failure and should prompt a call to the vet, not a wait-and-see approach.

When to see the vet

For a dog already diagnosed with heart disease, most cardiologists recommend rechecks every 3 to 6 months, with more frequent visits if the disease is advanced or recently diagnosed. In between visits, several changes should prompt a phone call or appointment.

Call your vet soon if your dog has:

• A new or worsening cough, especially at night
• A resting respiratory rate consistently above 40
• Exercise intolerance that seems to be getting worse
• Loss of appetite or weight loss
• Any change in energy level or interest in activities

Seek emergency care immediately if your dog has:

• Labored breathing, open-mouth breathing, or extreme panting at rest
• Blue, gray, or pale gums
• Collapse or fainting
• A sudden swollen belly
• Coughing up foamy, pink-tinged fluid
• Seeming unable to lie down comfortably or obviously struggling to breathe

Prognosis: what to expect

Prognosis for canine heart disease varies widely based on type, stage, breed, and response to treatment, but the overall picture is more hopeful than many owners realize.

For dogs with mitral valve disease diagnosed at Stage B1, many live out their natural lifespan without ever developing heart failure. For Stage B2 dogs started on pimobendan, the average time until heart failure is roughly 15 months longer than without treatment. For dogs in Stage C congestive heart failure, median survival with modern multi-drug therapy is approximately 9 to 12 months, with many dogs living significantly longer. Some dogs live 2 or 3 years after their first heart failure episode with good management.

DCM has a more variable course. Doberman Pinschers often progress faster than other breeds, and sudden death from arrhythmia is a real risk. Dogs with diet-associated DCM often improve substantially with a diet change and treatment. Cocker Spaniels with DCM often respond very well to taurine supplementation.

These numbers are averages, not verdicts. Some dogs do better, some worse, and the quality of the months is often far more important than the number of them.

Living well with a dog in heart failure

A heart disease diagnosis is frightening, but it is not the end of the life you share with your dog. Most dogs, once stabilized on medication, feel notably better than they did when they were first diagnosed. The cough settles, the energy returns at a modest level, the appetite comes back. You will likely find that you become intimately familiar with your dog's breathing, that you learn to recognize a good day from a bad one, and that you come to appreciate the small rhythms of his life in a way you might not have before.

Advocate for a thorough workup. Ask about pimobendan early if your dog has an enlarged heart. Count his breaths at night. Keep in touch with your vet. Watch for the changes that matter and let the rest slide. Heart disease in dogs is a serious diagnosis, but it is also, for most dogs, a manageable one. With the right care, many, many good days are still ahead of you both: quiet mornings, slow walks, the settled weight of him against your leg on the couch. Those days are worth protecting, and worth all the pill-giving, respiratory-rate-counting, low-sodium-treat work it takes to keep them coming.

This article provides general information about heart disease in senior dogs. Every dog is different, and diagnosis, staging, and treatment decisions should always be guided by a veterinarian who can examine your dog and interpret his specific imaging, bloodwork, and history. Never start, stop, or change the dose of cardiac medications without veterinary guidance, and never give over-the-counter human medications to a dog with heart disease. If your dog shows signs of severe breathing difficulty, collapse, blue gums, or a suddenly swollen abdomen, seek emergency veterinary care immediately.