Can Heart Murmurs Go Away In Dogs? | What Changes Over Time

Some dog heart murmurs fade once the trigger clears, but many adult-dog murmurs persist and need planned rechecks.

A “heart murmur” can mean heart disease. It can also be a short-lived finding. A murmur is extra noise your veterinarian hears when blood flow gets turbulent. The sound is a clue, not a diagnosis.

What happens next depends on the cause, your dog’s age, and any symptoms. Here’s how to tell when murmurs can go away, when they usually don’t, and what to track at home.

What A Heart Murmur Is In Plain Terms

Your dog’s heart should create a crisp “lub-dub.” A murmur is the swish in between when blood flow isn’t smooth. Turbulence can come from normal growth in puppies, short-term circulation changes, or structural heart disease.

Vets describe murmurs by timing, location, and loudness. Loudness is graded from I to VI. Merck’s veterinary manual notes that murmur features like timing and intensity can correlate with certain cardiac problems and that grading is part of the standard exam. Merck Veterinary Manual’s murmur overview summarizes how clinicians use those details.

Grade still has limits. A loud murmur can come from a small jet of fast flow. A quieter murmur can sit alongside heart enlargement. That’s why trends plus imaging beat a single number.

Can Heart Murmurs Go Away In Dogs? Cases Where They Can

Yes, some murmurs fade or disappear. The common thread is that the driver of turbulence resolves.

Innocent Murmurs In Puppies

Puppies can develop soft, low-grade “innocent” murmurs during growth. Cornell’s canine health team notes that many are outgrown by about six months of age, with an echocardiogram advised if the murmur persists. Cornell’s heart murmur article explains why rechecks still matter even when the first exam sounds mild.

A puppy who tires fast, breathes hard at rest, faints, or fails to grow normally needs faster evaluation. A louder murmur in a young dog also raises concern for a congenital defect.

Short-Term High-Flow States

Some murmurs are “flow murmurs.” Fever, pain, anemia, and dehydration can raise heart rate and change blood viscosity. When the underlying issue is treated and circulation settles, the murmur may soften or disappear.

These cases often start with basic testing, then a recheck listen after the dog is stable.

When A Murmur Usually Stays

In many adult dogs, the murmur reflects a structural change in the heart. Structural changes rarely reverse on their own, so the sound tends to persist. It may stay stable for years, or it may creep up with time.

Degenerative Mitral Valve Disease In Small Breeds

For middle-aged and older small dogs, a new left-sided systolic murmur often points to myxomatous mitral valve disease (MMVD). This is a gradual change in the mitral valve that lets blood leak backward with each beat. The valve change doesn’t vanish, so the murmur usually doesn’t either.

The goal is to identify stage and track heart size. The ACVIM consensus guidelines lay out MMVD stages and the measurements used to decide when closer monitoring or medication makes sense. ACVIM consensus guidelines on MMVD is a core reference for that staging approach.

Congenital Defects

Some dogs are born with defects that create steady turbulence, such as subaortic stenosis or patent ductus arteriosus. These murmurs tend to be consistent and may be loud. Some defects can be treated with procedures, but the only way to know what you’re dealing with is to image the heart.

How Vets Figure Out What Your Dog Has

Diagnosis is a set of questions. Each step narrows the cause and sets the follow-up plan.

Listening Exam And Full Physical

Your vet notes timing, location, and grade, then checks pulses, gum color, breathing effort, and lung sounds. This decides urgency.

Bloodwork When The Dog Looks Unwell

If your dog is pale, weak, or feverish, bloodwork can reveal a high-flow trigger like anemia. It also sets a baseline before many heart medications.

Chest X-Rays And Echocardiography

Chest x-rays show heart size and lung patterns. Echocardiography shows valve motion, chamber size, and the direction and speed of blood flow. For most dogs, an echocardiogram is the clearest way to confirm the cause behind the murmur.

Blood Pressure And Rhythm Testing

Blood pressure helps spot hypertension that adds workload. ECG testing checks for arrhythmias that can drive weakness or fainting.

Table: Common Murmur Situations And What To Do Next

Use this as a sorter when you’re deciding whether you’re in “recheck soon” territory or “image now” territory.

Situation	What It Often Suggests	Next Step
Soft murmur in a puppy, no symptoms	Innocent/physiologic flow murmur	Recheck at vaccine visits; echo if it persists past ~6 months
Puppy murmur that is loud or widespread	Possible congenital defect	Echocardiogram and cardiology referral
New murmur plus pale gums or low energy	Anemia or other high-flow state	Bloodwork; treat cause; re-listen after recovery
Middle-aged small dog, left-sided systolic murmur	MMVD	Baseline echo or radiographs; stage-based follow-up schedule
Large-breed dog with irregular rhythm	Arrhythmia with or without muscle disease	ECG plus echo; consider Holter monitoring
Murmur with cough that worsens at night	Airway disease, heart enlargement, or lung fluid	X-rays to separate airway vs heart causes
Murmur grade shifts between visits	Stress, hydration shifts, fever, progression, or examiner variation	Track trends; pair listening exams with imaging
Murmur plus fainting episodes	Arrhythmia, outflow obstruction, or advanced disease	Urgent ECG/echo; discuss emergency plan

What “Going Away” Means In Daily Life

Sometimes the murmur truly disappears. Often, owners see a softer sound one visit and a louder sound the next. That swing can happen with stress, hydration, and heart rate.

A useful way to think about it is this: if the trigger is temporary, the murmur can fade and stay gone. If the trigger is structural, the murmur may stay, even while your dog feels normal.

Home Checks That Give You Useful Clues

You can’t grade a murmur at home, but you can track signs that correlate with heart and lung strain.

Resting Breathing Rate

When your dog is asleep or fully relaxed, count breaths for 30 seconds and double it. Do it a few times a week. A steady rise from your dog’s usual baseline is a red flag.

Stamina And Recovery

Note how your dog recovers after a normal walk. If they stop sooner, lag behind, or take longer to settle, that trend is worth sharing with your vet.

Cough And Sleep Comfort

A new cough, lower appetite, or a dog that won’t lie down comfortably can signal heart or lung trouble. Airway disease can mimic this, so the symptom doesn’t diagnose anything on its own.

Table: Tests Your Vet May Recommend And What Each One Answers

This is the translator for “Why are we doing this test?” in one glance.

Test	What It Can Show	Common Use
Physical exam	Murmur timing/location/grade plus pulses and lung sounds	Every visit; sets urgency for imaging
Complete blood count	Anemia, inflammation patterns	New murmur with illness signs
Chemistry panel	Kidney/liver status, electrolyte balance	Baseline before meds; follow-ups on treatment
Blood pressure	Hypertension that raises cardiac workload	Senior dogs; kidney disease; eye changes
Chest x-rays	Heart size and lung fluid patterns	Cough, breathing change, staging
Echocardiogram	Valve leaks, chamber size, flow direction and speed	Best test to define cause and stage
ECG or Holter	Arrhythmias that can trigger weakness or fainting	Irregular rhythm, collapse, breed screening

Recheck Timing And What It Usually Looks Like

Recheck timing is based on cause, grade, and your dog’s daily signs. A puppy with a soft murmur may only need a listen at the next vaccine visit. An adult dog with suspected MMVD often needs imaging to set a baseline, then repeat checks on a schedule that matches stage.

If your vet suggests “watch and wait,” ask what the next checkpoint is. A real plan has a date, a test list, and clear triggers for an earlier visit.

• After a new murmur is found: many clinics schedule a recheck within weeks to confirm the finding and decide on imaging.
• After a baseline echo or x-rays: rechecks often focus on trends, such as heart size, breathing rate, and any new cough.
• If new signs show up: a same-week visit may be needed, even if the last check was recent.

Medication timing also depends on staging. Some dogs with a stable murmur need no heart meds yet. Others benefit once measurements show enlargement or fluid risk. Your veterinarian can explain where your dog fits and why.

Questions Worth Bringing To The Visit

• What grade is the murmur, and where is it loudest?
• Do you suspect a flow murmur, a valve leak, or a congenital issue?
• What test would change our plan the most right now?
• How often should we recheck, and what signs should trigger an earlier visit?
• If MMVD is likely, what stage do you suspect today, and what measurement would confirm it?

When To Seek Care Fast

A murmur with no symptoms can often be handled through routine scheduling. These signs call for prompt evaluation:

• Breathing trouble, open-mouth breathing at rest, or a resting rate that stays higher than your dog’s baseline
• Collapse, fainting, or sudden weakness
• Blue, gray, or persistently pale gums
• A belly that swells quickly or fluid in the limbs
• A cough paired with low appetite or a dog that won’t lie down comfortably

If you’re torn between “wait” and “go,” err on being seen.