My Dog Has a Heart Murmur and Needs an Anaesthetic: What Your Vet Checks
Mitral valve disease affects about 1 in 10 dogs in general practice. How vets judge anaesthetic risk when a murmur is found, and which questions to ask.
Written by thecanineledger
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If your dog is breathing fast at rest, coughing, struggling to breathe or has collapsed, call a vet now. Don’t wait for a planned procedure.
Our note: These signs are ours, not the review’s. If a dog with a known murmur develops a new cough, call your vet.
Mitral valve disease, a slow wearing of one of the heart’s valves, “is the most common cardiac disorder in dogs, affecting approximately 10% of dogs in primary care veterinary practice.” The review notes that such dogs often need an anaesthetic for routine procedures (Levinzon et al., Journal of Small Animal Practice 2026 ⚠️ narrative review).
While a murmur makes owners nervous, the review says “current evidence suggests that with appropriate modifications and monitoring, anaesthetic risk might not be significantly increased for subclinical cases.” Subclinical means the dog has no signs of heart failure. The key is knowing how far the disease has gone.
1. About this source
What it is. A narrative review by authors at a US veterinary school. It sets out a practical approach for vets in general practice. It is not a trial, and the authors chose which studies to include.
Funding. A US charitable foundation funded the work. The authors declare no conflicts of interest.
Our note: This is a review, and we haven’t read the studies behind it.
2. Stages of the disease
The review uses the standard staging system from the American College of Veterinary Internal Medicine (ACVIM):
| Stage | What it means |
|---|---|
| B1 | The valve leaks, but the heart hasn’t enlarged |
| B2 | The heart has enlarged, but there are no signs of heart failure |
| C | Signs of heart failure, such as fluid on the lungs |
Why the stage matters. Dogs in stage B2 carry more anaesthetic risk than B1. If chest x-rays show fluid on the lungs (stage C), the review says that is a reason not to go ahead with a planned procedure until the heart is stable.
Wide variation. Even within stage B2, “some dogs barely meet treatment thresholds while others approach congestive heart failure.”
→ Cavalier King Charles Spaniel Health: Why the Heart Comes First · → Heart Failure at Home: Counting Your Dog’s Sleeping Breaths
3. How vets work out the stage
The best test. A full heart scan (echocardiogram) by a specialist is the gold standard. The review notes that referral “is often cost‐prohibitive and might involve long waiting periods.”
Other options in general practice.
- Listening carefully to the murmur, and checking pulse, gum colour, heart rate and breathing rate.
- Chest x-rays, which can measure heart size.
- A blood test for a marker that rises with heart strain.
- A quick heart scan by the vet in the practice.
The review gives ranges where results are unclear, and says those dogs may need further tests or referral.
Our note: We’ve described these tests in plain words and left out the review’s cut-off values.
4. During the anaesthetic
The review says vets can adjust the drugs and fluids they use for dogs with mitral valve disease, and that close monitoring matters. It cites one referral-centre study in which dogs with heart disease having routine dental work had no more complications or deaths than healthy dogs. We didn’t read that study.
→ How Risky Is Anaesthesia for My Dog? · → Pre-Anaesthetic Bloodwork: What It Finds, and When It Matters
5. Questions to ask your vet
- What stage is my dog’s heart disease, and how sure are you?
- Do we need x-rays, a blood test or a scan before the anaesthetic?
- Should my dog keep taking any heart medicine on the day?
- How will my dog be monitored, during and after?
Our note: These questions are ours. Ask your vet whether your dog should have its heart medicine on the day of the anaesthetic.
6. What we could not verify
| Commonly said | What we found |
|---|---|
| “A dog with a murmur can’t have an anaesthetic” | Not so, for most. The review says risk may not rise much without heart failure. |
| “Every dog with a murmur needs a specialist scan first” | Ideal, but not always possible. The review sets out other tests. |
| “All murmurs carry the same risk” | No. Risk depends on the stage, and varies within stages. |
Sources
- Levinzon I, Estrada A, et al. Pre-anaesthetic risk assessment and management of dogs with myxomatous mitral valve disease: a spectrum of care narrative review. J Small Anim Pract 2026 ⚠️ narrative review: University of Florida authors. Funded by a US charitable foundation
Always confirm with your vet before acting on anything on this page.