Heart Murmurs and Heart Disease in Senior Dogs
A heart murmur in dogs is a sound your vet hears, not a diagnosis by itself. Hearing that your dog has a heart murmur can be unsettling. But it doesn’t have to be a cause for immediate alarm. Many senior dogs live comfortably with a murmur for years, especially when it’s caught early and monitored carefully. Knowing what the diagnosis means and what to watch for helps more than worrying in the dark.
Quick note: This article is for general education and isn’t a substitute for veterinary advice. Only your vet can grade and stage your dog’s specific heart condition.
Key takeaways:
- A heart murmur in dogs needs a vet’s follow-up, so ask about next steps.
- Many murmurs in older dogs come from valve disease, and early tests help plan care.
- Call your vet quickly if your dog coughs more, breathes fast at rest, or tires easily.
What a Heart Murmur in Dogs Actually Is
A heart murmur is an abnormal sound from turbulent blood flow in the heart. Vets usually hear it with a stethoscope during a routine exam, often before any symptoms show. Vets grade murmurs from I to VI based on how loud they are. A Grade I murmur is very soft and may only be audible in one spot. A Grade VI is loud enough to feel with a hand on the chest.
Important: grade alone doesn’t determine severity or prognosis. A loud murmur isn’t automatically more dangerous than a soft one. What matters more is the cause and how well the heart works.
The Most Common Cause: Mitral Valve Disease
In small and medium senior dogs, the most common cause is myxomatous mitral valve disease (MVD). The valve between two heart chambers wears down and no longer closes properly. As a result, blood leaks backward instead of moving forward efficiently. It usually develops between 6 and 10 years of age. Often, a murmur is the very first sign, before any other symptoms appear. Mitral valve disease is the most common cause of a heart murmur in dogs.
In large and giant breeds like Doberman Pinschers and Great Danes, dilated cardiomyopathy (DCM) also matters. DCM weakens the heart muscle itself. It can show up differently, sometimes suddenly, even with collapse.
How the Disease Progresses: The Stages
Vets commonly use a staging system to track heart disease over time:
- Stage B1 — A murmur is present, but no other changes yet. This is usually the longest stage, and treatment often isn’t needed yet. Still, a check-up about every 6 months helps catch changes early.
- Stage B2 — The heart has started to change shape and enlarge. Treatment usually begins here to slow progression and delay the onset of symptoms.
- Stage C — Clinical signs of heart failure appear, such as coughing, exercise intolerance, or labored breathing. Monitoring shifts to every 3-6 months, and treatment is adjusted accordingly.
- Stage D — More advanced heart failure with stronger symptoms, sometimes including arrhythmias, despite ongoing treatment.
Symptoms to Watch For as the Disease Progresses
- Coughing, especially at night or after lying down
- Reduced desire or ability to exercise
- Labored or rapid breathing
- Fatigue or reduced stamina
- In more advanced cases, fainting or collapse
If your dog has a known murmur and shows any of these signs, call your vet promptly. Don’t wait for the next scheduled check-up.
A Useful Home Monitoring Tool: Resting Respiratory Rate
One of the most useful things you can do at home is track your dog’s Resting Respiratory Rate (RRR). Simply count breaths per minute while your dog is calm and asleep. A gradual rise in RRR can signal fluid buildup before a cough or other symptoms appear. That gives you and your vet an early warning to act on.
Treatment and Outlook
Treatment depends on the stage. It can include heart medications, diet changes, and, in select cases, surgery. If weight loss becomes an issue, your vet may suggest a richer, tastier diet. Your vet may also suggest gentle exercise that fits what your dog can handle now. Always plan it with your vet, since capacity changes by stage. Treatment for a heart murmur in dogs depends on the cause and the stage.
The outlook is often better than owners expect. With good treatment, many dogs enjoy a good quality of life for a meaningful time, even after congestive heart failure. Survival from that point often averages 12 to 18 months. However, this varies a lot by dog and by how early treatment started.
The Bottom Line
A heart murmur in dogs is common in seniors and very manageable, especially when caught early. It’s often the first sign of a slow condition, not an emergency. Regular vet check-ups help a lot, and many vets suggest two a year for seniors. Tracking resting breathing at home also helps. So does following your vet’s plan, which gives your dog the best chance at a long, comfortable life. A heart murmur in dogs needs a vet’s follow-up, so ask about next steps.
Further reading: Also, for more detail from veterinary organizations, see ACVIM’s resources on canine heart disease, the Merck Veterinary Manual, and the AAHA Senior Care Guidelines.
Finally, we last updated this guide in October 2026.