Dog heart murmur grade 5 and grade 6 life expectancy

A grade 5 or grade 6 heart murmur does not come with a set life expectancy. The grade describes how loud the murmur is, not how much time a dog has left. What decides the outlook is the cause of the murmur, whether the heart has enlarged, and whether congestive heart failure has started.

The most common case is an older small dog with a loud murmur from mitral valve disease. If there is no heart failure yet, that dog often lives another one to several years, and many die of something unrelated. Once heart failure has started, commonly reported survival on medication is roughly six months to a year and a half, with some dogs living longer. These are broad ranges, and the vet or cardiologist who has seen your dog's heart scan is the one who can narrow them.

What grade 5 and grade 6 mean

Vets grade murmurs from 1 to 6 by listening with a stethoscope.

There is no meaningful difference in outlook between a 5 and a 6. Both are simply very loud. Our guide to heart murmurs in senior dogs and cats explains the grades and causes in more detail.

Why a loud murmur matters more in some dogs than others

In mitral valve disease, the cause of most murmurs in older small dogs, louder murmurs do tend to go with more advanced disease. A grade 5 or 6 usually means the valve is leaking a lot, and the heart has often enlarged to cope. It does not mean the dog is in heart failure. Many dogs with very loud murmurs are comfortable and active for a long time.

Loudness is a much poorer guide with other causes. In large breeds with dilated cardiomyopathy, the murmur can be soft while the disease is severe. This is why the grade alone cannot give a life expectancy.

How long can a dog live with a grade 5 heart murmur?

For mitral valve disease, vets use lettered stages. The stage, not the grade, is what the commonly reported figures are based on.

A dog with a grade 5 murmur is most often in stage B2 or C. Which one makes a large difference, and it cannot be told from the stethoscope.

Dog heart murmur grade 6 life expectancy

The answer is the same as for grade 5. A grade 6 murmur in a dog who breathes easily at rest, eats well and still enjoys walks can point to a heart that is coping for now. The same murmur in a dog who is breathing fast, restless at night or fainting needs a vet now.

Heart murmur life expectancy when the dog is coughing

A cough in a dog with a murmur does not by itself mean heart failure, so it does not by itself shorten the estimate. There are three usual explanations:

• Fluid in the lungs from heart failure. This usually comes with fast or labored breathing, not a cough alone.
• An enlarged heart pressing on the airways. The dog coughs, often when excited or lying down, but is not in failure.
• Airway disease unrelated to the heart. Collapsing trachea and chronic bronchitis are common in the same older small breeds that get mitral valve disease.

Chest X-rays are how a vet tells these apart. If the cough turns out to be airway disease, the heart outlook is unchanged. If the X-rays show fluid, the dog is in stage C and the figures for congestive heart failure in senior dogs apply. The other causes of coughing in old dogs are worth reading alongside.

The most useful thing to track at home is the breathing rate while your dog is asleep. Count breaths for a full minute. Most dogs, including dogs with well-controlled heart disease, stay under about 30. Ask your vet what number should prompt a call for your dog, and keep a note of the counts.

What an echocardiogram changes

An echocardiogram is an ultrasound scan of the heart, usually done without sedation. It shows what is causing the murmur, how badly the valve leaks and whether the heart chambers have enlarged. That gives the stage, tells the vet whether medication should start now, and makes any life-expectancy estimate far more specific. If a cardiologist is not within reach, chest X-rays give some of the same information.

What medication changes

In stage B2, a heart medicine called pimobendan is commonly prescribed. In a large clinical trial of dogs with enlarged hearts from mitral valve disease, it delayed the start of heart failure or heart-related death by about 15 months on average. That is the main reason vets want to know the stage before signs appear.

In stage C, vets add a diuretic to clear fluid from the lungs, usually with other heart medicines. Many dogs breathe and feel much better within a day or two, and then need rechecks of kidney values. The choice of drugs and every dose are set by the prescribing vet for your dog's weight, kidneys and other medicines. Do not change, skip or stop them without asking, and never give a dog a heart or water tablet prescribed for a person.

How long can an old dog live with a heart murmur?

Often a long time. Mitral valve disease usually moves slowly, over years, and plenty of old dogs die with a murmur, not from it.

Take a 14-year-old small dog with a grade 5 murmur. That dog is already near or past the usual lifespan for many breeds, as the pet age calculator will show. If the heart is not in failure, a year or several is often realistic, and something other than the heart may well be what ends his life. If he is in heart failure, the stage C range applies, with age adding a few complications:

• Kidneys. Diuretics are hard on the kidneys, and many old dogs have reduced kidney function. The vet balances the two with regular bloodwork.
• Other medicines. Arthritis and other drugs may need adjusting. Human painkillers such as ibuprofen, naproxen, aspirin and acetaminophen can seriously harm or kill dogs and must not be given.
• Anesthesia. Dental work and surgery are not ruled out, but the vet will want to know the stage first.

What progression looks like

• A sleeping breathing rate that creeps up over days
• A cough that gets worse at night or after lying down
• Tiring sooner on walks, and restlessness at night
• Fainting or wobbling with excitement or exertion
• Eating less and losing muscle over the back and thighs

Call the vet today if

Call your vet or an emergency clinic now if a dog with a heart murmur:

• Is breathing fast or with effort while resting or asleep, or the sleeping rate is above the number your vet gave you
• Cannot settle or will not lie down, and stands or sits with the neck stretched out
• Has gums or a tongue that look blue, gray or very pale
• Faints or collapses
• Coughs up foam or pink-tinged fluid
• Develops a swollen belly
• Stops eating, or vomits and cannot keep heart medicines down

Difficulty breathing is an emergency at any hour.

This article is general educational information about heart murmurs in dogs and is not veterinary advice. Survival figures are commonly reported ranges that vary widely, and a murmur grade alone cannot tell you how long a dog will live. Testing, medication and prognosis for your dog should be decided with your veterinarian or a veterinary cardiologist.