Heart murmur in dogs: what it means, grades 1-6, and monitoring at home
A heart murmur in dogs is an abnormal sound caused by turbulent blood flow through the heart, graded 1 to 6 by loudness. It is a finding, not a diagnosis. The most common cause is mitral valve disease, especially in small breeds. Maven Pet monitors resting respiratory rate through the collar to catch progression days before visible symptoms appear.
A heart murmur in dogs doesn't always mean abnormal breathing at rest.
A heart murmur diagnosis can feel scary, but a murmur is not a diagnosis by itself. It's a sound your vet hears, and the cause can range from harmless to heart-related. This is what Maven's resting breathing data shows about heart murmurs in dogs, based on 36 dogs with a declared murmur, and when the pattern may be worth watching more closely.
What is a heart murmur in dogs?
A heart murmur is an abnormal sound caused by turbulent blood flow through the heart. It's not a disease on its own. It's a finding your vet hears through a stethoscope, and it's graded 1 through 6 based on how loud it is. The grade tells you how easy it is to hear. It doesn't directly tell you how sick your dog is, though higher grades do tend to signal more advanced changes.
The most common cause in dogs is mitral valve disease (MVD), where the valve between the left chambers of the heart starts to leak. Small breeds, especially Cavalier King Charles Spaniels, Dachshunds, and Shih Tzus, are prone to this. It can progress slowly over years, or faster, depending on the dog.
Very soft, heard only in a quiet room by an experienced vet. Often found incidentally during a routine exam. Most dogs at this stage have no symptoms. Starting to monitor now builds the baseline your vet will need later.
Quiet but clearly heard. Still considered mild. The heart is likely compensating well. Establishing a personalized health baseline now means any future shift in activity, sleep, or breathing will be immediately visible.
Moderate intensity. Your vet will likely recommend more frequent check-ins and may start discussing cardiac medication. Tracking trends in activity and respiratory rate between appointments helps your vet make those timing decisions with real data.
A loud murmur heard on both sides of the chest. At this stage cardiac medication is likely on the table. Daily monitoring of breathing rate, heart rate, and activity gives your vet objective data on how your dog is responding to treatment.
Very loud, with a palpable thrill through the chest. The dog is likely on cardiac medication and at higher risk of progression. Resting respiratory rate monitoring becomes essential at this stage to catch early signs of decompensation.
The most severe grade. Felt and sometimes heard without a stethoscope. Daily monitoring of breathing rate is critical at this stage.
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How Maven helps manage a dog with a cardiac heart murmur, at every stage
A heart murmur of cardiac origin, particularly those linked to mitral valve disease or cardiomyopathy, represents a progressive disease spectrum. Not every murmur dog is in immediate danger, but the condition can change over time, and those changes often show up in the data before they show up in the dog.
That's the core value of continuous monitoring. In early-stage disease, Maven establishes a personalized baseline for your dog's breathing rate, heart rate, activity, sleep, and drinking behavior. That baseline is what makes future deviations meaningful. Without it, there's nothing to compare against. With it, even a subtle upward drift in resting respiratory rate or a gradual drop in daily activity becomes visible and actionable.
In more advanced stages, particularly when a dog is at risk of or has developed congestive heart failure, resting respiratory rate becomes the critical signal. It's a well-established marker for pulmonary congestion, and it tends to rise before visible symptoms appear. Catching that trend early means a medication adjustment rather than an emergency visit.
Early stage: build the baseline now
In preclinical phases, your dog may look and feel completely normal. But Maven is already collecting the data that will make future changes detectable. A baseline built today is what gives your vet context six months from now.
Progressive disease: catch the trend, not the crisis
Subtle changes, a gradual rise in breathing rate, reduced activity, more fragmented sleep, often precede overt symptoms by days. Continuous monitoring surfaces these trends while the window to intervene is still open.
On cardiac medication: confirm it's working
If your dog is on Vetmedin, furosemide, or other cardiac medication, resting respiratory rate and activity trends tell you and your vet whether the current dose is doing its job. Without data, you're relying on guesswork between appointments.
Every appointment: show up with real data
Veterinary cardiologists are increasingly aware of Maven. Some already recommend it to clients. Weeks of breathing, heart rate, and activity trends change what's possible in a cardiology appointment, from impression to evidence.
What your vet asked you to do at home and why most people quietly stop doing it
The instructions: wait until your dog is fully asleep, tiptoe over, stay completely still, count chest rises for 30 seconds, multiply by two, write it down. Repeat daily. Your dog woke up when you walked over. Or you forgot. Or you counted 14 and weren't sure if that was right. This is not a criticism. It's just genuinely hard to do consistently, and the vets know it.
Set it up tonight. Your dog is monitored by morning.
The sensor attaches to whatever collar your dog already wears. It's small and light. Most dogs stop noticing it within an hour of putting it on.
The first week, Maven collects data to understand what's normal for your dog specifically, not a generic average. A 22 bpm baseline for a large dog means something different than the same number for a Cavalier.
If your dog's resting respiratory rate trends above their personal baseline, you get a notification. Not a scare. A heads-up with enough time to call your vet before it becomes urgent.
Download your dog's monthly health report PDF directly from the app, or share trend charts on the spot. Show your cardiologist actual numbers instead of "she seemed a little off last week."
What people with heart murmur and cardiac dogs say about Maven
"My dog has CHF and a murmur. The vet told me to get a cardio and respiratory tracker that cost almost $400. After doing my own research I found Maven. This tracker is affordable, accurate, and sends alerts when needed so I can take emergency action if I need to. I cannot recommend this enough."
"My 12-year-old was diagnosed with a heart murmur and MVD. Now I can actually see when he's within a safe resting respiratory rate or when he's creeping into unsafe territory and make a better call about what to do."
"My dog has mitral valve disease. Instead of guessing I know exactly how he's doing every day. If there's even a slight shift in his breathing I have the data to act immediately and advocate for him at the vet."
"My dog's cardiologist asked about the tracker so he could start recommending it to his other patients. That told me everything I needed to know about whether this is worth it."
"After my dog's CHF diagnosis, Maven gave me the confidence to keep an eye on her breathing without living in constant panic. I just check the app instead of lying awake listening to her breathe."
Your vet asked you to count breaths.
Can the sensor do the job?
For a dog with a heart murmur, home monitoring means tracking resting respiratory rate every night. Which only works if the sensor's count matches what a real veterinarian would count. A cardiology team at the University of Florida wanted to know.
They tested 19 dogs across 13 breeds. Independent vets counted breaths by hand while the sensor did its own count at the same moment. Across 120 side-by-side checks, the sensor and the vet agreed. Fluffy or sleek. Big or small. Same result.
Everything about monitoring a dog with a heart murmur
Start monitoring your cardiac dog tonight
One sensor. One app. The breathing data your vet needs from home. Cardiology monitors cost $400 or more. Maven is $13.99 a month with the sensor included. 30-day risk-free return policy.
Plans cover 1 pet. 2 and 3 pet options available at checkout. The sensor fits most standard collars and works for both dogs and cats.
Your vet said to watch their breathing. Now you actually can.
Maven is the only pet tracker that measures resting respiratory rate automatically. Set it up tonight. By morning you'll have your dog's first readings, and you can stop lying awake listening for changes you can't reliably count anyway.
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