Treatment for a heart murmur in dogs depends entirely on what’s causing it and how severe it is. A murmur itself isn’t a disease. It’s a sound created by turbulent blood flow through the heart, and it can range from harmless (common in puppies) to a sign of serious valve disease that needs medication or even surgery. Many dogs with low-grade murmurs need no treatment at all, while dogs with advanced heart disease may require multiple daily medications to manage symptoms and extend their lives.
What the Murmur Grade Tells You
Veterinarians grade heart murmurs on a scale from 1 to 6 based on how loud they are through a stethoscope. A Grade 1 murmur is so faint that a vet has to listen carefully in a quiet room for several minutes to detect it. A Grade 2 is soft but easy to hear within seconds. Grade 3 is moderate. Grade 4 is loud, and Grades 5 and 6 are so intense that a vet can actually feel the vibration through the chest wall. At Grade 6, the murmur is audible even after removing the stethoscope from the dog’s body.
The grade gives a rough sense of severity, but it doesn’t tell the whole story. A Grade 3 murmur in a puppy might resolve on its own as the heart grows, while the same grade in a 10-year-old Cavalier King Charles Spaniel likely signals progressive valve disease. Your vet will use the murmur grade alongside imaging (echocardiogram, chest X-rays) to determine what’s actually happening inside the heart and whether treatment is needed.
When No Treatment Is Needed
Not every heart murmur requires medication. Veterinary cardiologists use a staging system that classifies dogs into groups based on how far their heart disease has progressed, and the first two stages call for monitoring rather than treatment.
Dogs in the earliest stage are at higher-than-average risk for heart disease (certain breeds, for example) but have no murmur and no structural changes. No medication is recommended. Dogs with a murmur but no evidence of heart enlargement on X-rays or echocardiogram fall into the next stage. At this point, the heart is still compensating well, progression to heart failure is uncertain, and no drug or dietary treatment has been shown to help. These dogs typically get rechecked every 6 to 12 months so any changes can be caught early.
“Innocent” murmurs in puppies also fall into this category. Many puppies have soft murmurs that disappear by 4 to 5 months of age as their cardiovascular system matures.
Starting Medication Before Symptoms Appear
The critical turning point comes when imaging reveals that the heart has enlarged significantly, even though the dog still looks and acts completely normal. This is the stage where early treatment makes the biggest difference.
A landmark clinical trial called the EPIC study found that starting a heart-strengthening medication at this preclinical stage delayed the onset of congestive heart failure by approximately 15 months. Dogs on the medication went a median of 1,228 days before developing heart failure, compared to 766 days for dogs on placebo. That’s roughly 15 extra months of normal life before a dog needs more aggressive treatment.
The specific criteria that trigger this early treatment include a murmur of at least Grade 3, along with echocardiographic and X-ray measurements showing the left side of the heart has stretched beyond certain thresholds. If your vet recommends starting medication even though your dog seems fine, this is why. Waiting for visible symptoms means missing the window where early intervention is most effective.
Managing Active Heart Failure
Once a dog develops symptoms of congestive heart failure, including coughing, difficulty breathing, exercise intolerance, or fluid buildup, treatment typically involves a combination of medications working together. The standard regimen includes a diuretic to pull excess fluid from the lungs, the heart-strengthening drug started in the earlier stage, a blood pressure medication that reduces the workload on the heart, and a second mild diuretic that helps protect potassium levels.
These medications can be remarkably effective. Many dogs with well-managed heart failure return to near-normal activity levels and maintain a good quality of life for months to over a year. The key is consistent dosing and regular veterinary monitoring.
What to Watch for With Medications
The blood pressure medications used in heart disease (called ACE inhibitors) can occasionally affect kidney function. Your vet will run blood work before starting treatment and periodically afterward to check kidney values and potassium levels. Dogs with pre-existing kidney disease or dehydration are at higher risk for side effects, so close monitoring is especially important in those cases.
Less common side effects include loss of appetite, vomiting, diarrhea, weakness, or fainting episodes related to low blood pressure. If your dog takes anti-inflammatory pain medications for arthritis or another condition, mention this to your vet, as combining them with ACE inhibitors can stress the kidneys. In most dogs, these medications are well-tolerated, but any new lethargy, loss of appetite, or increased thirst and urination warrants a call to your vet.
Surgical Treatment for Specific Conditions
Some heart murmurs are caused by structural defects that can be fixed surgically. The most common example is patent ductus arteriosus (PDA), a condition where a blood vessel that should close shortly after birth stays open, forcing the heart to work much harder than normal. PDA is one of the most frequently diagnosed congenital heart defects in dogs and, if caught early, is highly treatable.
Closure can be done either through traditional surgery or a catheter-based procedure threaded through a blood vessel. Both approaches have excellent outcomes. In a study of 520 dogs, the mortality rate within the first three days after the procedure was just 2.6%, and one-year and two-year survival rates were 92% and 87% respectively. Many of these dogs go on to live normal lives with no ongoing medication. The key is early detection: untreated PDA leads to heart failure, often within the first few years of life.
Mitral valve repair surgery, which directly fixes the leaking valve responsible for most heart murmurs in older small-breed dogs, is now performed at a handful of specialized veterinary centers. It can be curative, but availability is limited and costs are significant, putting it out of reach for many owners.
Diet and Nutrition Changes
Sodium restriction plays a supporting role in managing heart disease, though the degree of restriction depends on the stage. Dogs with mild heart disease (murmur present but no symptoms) need only mild sodium reduction. Dogs in active heart failure benefit from more significant restriction. If you use pill pockets or treats to give your dog medication, check the label: aim for treats with less than 100 mg of sodium per 100 calories.
Omega-3 fatty acids from fish oil can help dogs with heart disease, particularly those losing muscle mass (a condition called cardiac cachexia that affects dogs in later stages of heart failure). A commonly cited dosage is 40 mg of EPA and 25 mg of DHA per kilogram of body weight daily. For a 22-pound dog, that works out to roughly 400 mg of EPA and 250 mg of DHA per day. Use a fish oil product made for dogs or a purified human-grade supplement, and confirm the dose with your vet.
Maintaining a healthy body weight is also important. Overweight dogs force their hearts to work harder, while dogs losing weight due to advanced heart disease may need calorie-dense foods to maintain muscle.
Monitoring Your Dog at Home
One of the most valuable things you can do at home is count your dog’s resting respiratory rate. While your dog is sleeping or resting calmly, count the number of breaths (one inhale plus one exhale equals one breath) over 30 seconds and multiply by two. Dogs with well-controlled heart disease typically breathe fewer than 30 breaths per minute at rest. A consistent reading above 30, or a noticeable upward trend from your dog’s normal baseline, can be an early warning sign that fluid is building up in the lungs, often catching a problem days before other symptoms become obvious.
Get in the habit of tracking this number a few times per week and recording it. Many veterinary cardiologists consider home respiratory rate monitoring one of the single most useful tools for owners of dogs with heart murmurs. Several free smartphone apps are designed specifically for this purpose.
Beyond breathing rate, watch for decreased interest in walks or play, coughing (especially at night or after lying down), restlessness at bedtime, or a visibly swollen belly, which can indicate fluid accumulation in the abdomen. Catching changes early gives your vet more options and generally leads to better outcomes.