Last Updated: 24/11/2025
Heart Disease in Dogs: A Vet’s Guide to Signs, Causes and Treatment
Has your vet mentioned a heart murmur? Learn about the common causes of heart disease in dogs, including Mitral Valve Disease and DCM. Our vet guide covers symptoms, diagnosis, treatment options, and the best diets for cardiac support.
Author: Dr Michelle Wong BVSc
Reading Time: 9 minutes - short read
Hearing the words "heart murmur" or "heart disease" during a routine vet visit can be daunting for any pet parent. It’s a scary concept, but knowledge is truly power when it comes to managing your furry friend's ticker. While some heart conditions are congenital (present from puppyhood), others are acquired as our dogs age. Whether you have a cheeky Cavalier or a dignified Doberman, understanding the specific condition is the first step in helping them live a happy, comfortable life. This guide breaks down the complexities of canine cardiology into simple terms to help you navigate the journey ahead and ensure your pooch gets the best care possible.
Causes of heart disease in dogs
While there are multiple causes of heart disease in dogs, the most common forms diagnosed are Mitral Valve Disease and Dilated Cardiomyopathy.
Mitral Valve Disease in Dogs
Mitral valve disease is the most frequent heart condition diagnosed in small dogs. To understand how it works, it helps to picture the heart as a pump with four distinct rooms.
How a healthy heart works
The heart is split into top rooms (atria) and bottom rooms (ventricles). In a healthy dog, the heart functions like a precise machine:
- Blood enters the top room (left atrium).
- It gets pumped down into the bottom room (left ventricle).
- From there, it is pumped out to the rest of the body to deliver oxygen.
Separating these rooms are valves, which act like one-way doors. Their only job is to snap shut to keep blood flowing forward, preventing it from slipping back into the previous chamber.
What happens in mitral valve disease
The Mitral valve separates the left atrium from the left ventricle. In dogs with MVD, this valve begins to degenerate or wear out. Instead of closing tightly like a sealed door, the valve becomes thickened or floppy.
Because the seal is broken, some blood leaks backwards into the top chamber (the atrium) every time the heart beats. Veterinarians call this "regurgitation." Over time, this backflow causes fluid to build up in the lungs, which can eventually lead to congestive heart failure.
Dilated Cardiomyopathy
While small dogs are prone to valve issues, large breed dogs are more commonly affected by a condition called Dilated Cardiomyopathy (DCM).
What happens to the heart?
DCM is often an inherited condition where the heart muscles become weak and flimsy. Because the muscle walls are weak, the heart cannot contract strongly enough to pump blood effectively.
To compensate for this weakness, the heart muscle stretches and enlarges (dilates) to try and hold more blood. This works for a little while, but eventually, the heart becomes like an over-stretched balloon. It can no longer cope with the pressure, leading to fluid accumulation in the chest and congestive heart failure.
The role of nutrition
While genetics play a huge role, nutrition is also a key factor. DCM has been linked to deficiencies in taurine, an amino acid essential for healthy heart development and function.
This is particularly important for dogs on vegetarian or vegan diets, as taurine is naturally found in meat. Pet parents feeding these diets should be vigilant about appropriate supplementation to protect their dog's heart health.
Does a Grain-free diet cause heart disease in dogs?
Many pet parents choose to go grain free in an effort to find the healthiest possible food for their pets, so naturally when the FDA announced in July 2018 that they were investigating a potential link between grain free dog food and heart disease, it's no wonder many were left wondering whether they had made the right choice.
The FDA released an update regarding their investigation into this issue on 27th June 2019 and while some common dietary factors between many of the cases have been identified, particularly the feeding of grain free diets and diets containing peas and/or lentils, the root cause is still yet to be determined. At this stage there is still no definitive evidence to link the cases to diet altogether, although identifing a specific dietary link between cases remains the primary focus of the investigation.
For more information, take a look at our article on Does Grain Free Dog Food Cause Heart Disease?
Heartworm and heart disease
Heartworm infection can also cause heart disease in dogs. It is important to worm your pet regularly. Heartworm is spread by mosquitoes and will lead to serious lung disease and heart failure. This is a fatal disease if not treated. However, treatment for heartworm can also be complicated and dangerous. Prevention is easy with a range of heartworm products available.
For more information, check out our 6 Fact You Need to Know about Heartworm.
Breeds most at risk
A number of large dog breeds have been associated with Dilated Cardiomyopathy, most notably:
- Doberman Pinschers
- Boxers
- Standard Schnauzers
- Great Danes
- Irish Wolfhounds
- Newfoundlands
- Dalmatians
- Cocker Spaniels
- Portugese Water Dogs
Mitral valve disease on the other hand, commonly presents in senior small dogs. The Cavalier is the most commonly affected breed, but other small breeds are often affected such as
Signs to watch for
There may be little to no symptoms initially, but your veterinarian may pick up a heart murmur at an annual vaccination or health check appointment. As the disease progresses, there may be fluid accumulation in the chest leading to congestive heart failure.
Signs of congestive heart failure
- Coughing
- Lethargy
- Exercise intolerance
- Shortness of breath or trouble breathing
- Pale or blue-ish gums
- Collapse
- Fluid in the abdomen (depends on the heart condition, usually occurs with right sided heart failure)
How is heart disease diagnosed?
Identifying heart disease usually begins during a routine consultation. During a physical exam, the vet will use a stethoscope to listen to the chest for specific warning signs.
A strong suspicion of heart disease is raised if the vet hears:
- A heart murmur: A "whooshing" sound caused by turbulent blood flow.
- Abnormal lung sounds: Such as crackles (indicating fluid) or muffled breathing.
Further investigation If these sounds are detected, the vet will need to look inside the chest to understand what is going on. This typically involves:
- Chest x-rays: To assess the size of the heart and check the lungs for fluid.
- Referral to a cardiologist: In many cases, a specialist is required for an echocardiogram. This is essentially an ultrasound of the heart (similar to pregnancy scans in humans) and allows for a definitive diagnosis by letting the vet see the heart valves and muscles in action.
Treatment options
Because every dog is unique, treatment plans are tailored to the individual and the specific type of heart disease they have. The ultimate goal is always the same: to extend your dog's life and, most importantly, improve their daily quality of life so they can keep being their happy selves.
Common medications
Heart failure is typically managed with a combination of drugs designed to support the heart's function:
- Pimobendan: This is a cornerstone medication for both Mitral Valve Disease and Dilated Cardiomyopathy. It acts like a dual-engine booster: it strengthens the heart muscle so it can pump more effectively, and it widens the blood vessels (vasodilation). This makes it much easier for the heart to push blood forward to the rest of the body.
- ACE Inhibitors: These are often used alongside Pimobendan. They also help relax and widen blood vessels, reducing the pressure the heart has to pump against.
- Diuretics: If the heart isn't pumping well, fluid can back up into the lungs. Diuretics, such as Furosemide, are used to clear this fluid accumulation, helping your dog breathe comfortably again. In severe cases, additional types of diuretics may be added.
Monitoring is key
Heart medication is not a "set and forget" solution. Because diuretics work through the kidneys, it is vital to take your dog in for regular check-ups and blood tests. This allows the vet to monitor kidney function and electrolyte levels to ensure the medication remains safe and effective.
Diet and nutrition for heart health
Just like in humans, diet plays a massive role in managing heart health. Your veterinarian may recommend transitioning your dog to a low-sodium diet, particularly if their condition has progressed to congestive heart failure.
Why reduce sodium? Salt acts like a sponge in the body - it holds onto water. In a dog with heart failure, the body is already struggling to move fluid around. High levels of sodium cause the body to retain even more fluid, which increases the workload on the heart and worsens fluid build-up in the lungs.
Choosing the right food
- Senior diets: These are generally formulated with lower sodium levels than standard adult maintenance foods, making them a better option for older dogs with mild changes.
- Prescription diets: For the best therapeutic effect, your vet may prescribe a clinical heart-health diet. These are scientifically formulated to have severely restricted sodium levels while maintaining high palatability (because we know heart dogs can be fussy eaters!).
Important note: Always consult with your veterinarian before switching your pet's food to ensure it meets their specific medical needs.
Managing heart disease at home
Once a dog begins heart medication, it is almost always a lifelong commitment. However, managing heart disease isn't just about the medicine cabinet; it also requires some adjustments to your daily routine.
Exercise and activity
For dogs with mild symptoms or those in the earlier stages of disease, staying active is beneficial. However, the pace needs to change.
- Light exercise: Think gentle "sniffaris" rather than high-intensity ball chasing.
- Listen to their body: Monitor them closely. If they lag behind on a walk, sit down, or seem weak, it is time to stop.
- Rest is best: In severe cases, your vet may recommend strict rest to reduce the strain on the heart. Always follow your vet's specific exercise plan.
Monitoring at home: The 30-breath rule
One of the most useful things a pet parent can do is monitor their dog's Resting Respiratory Rate. This helps detect if the heart disease is progressing or if fluid is building up in the lungs (pulmonary oedema).
How to do it:
- Wait until your dog is sleeping.
- Count the number of breaths they take in one minute. (One breath = chest rising and falling).
- The Guideline: A normal sleeping rate is usually under 30 breaths per minute. If you consistently notice the rate rising above 30 breaths per minute, contact your veterinarian immediately.
Life expectancy
It is natural to worry about how much time you have left with your furry friend. Life expectancy varies significantly depending on the severity of the heart failure and how well they respond to treatment. With the right care, many dogs can live comfortably for months to years after diagnosis.
FAQs
While a diagnosis of heart disease is serious, it is manageable with the right team in your corner. By combining veterinary-prescribed medication with lifestyle adjustments - such as weight management, controlled exercise, and a low-sodium diet - you can significantly improve your dog's quality of life.
Remember to monitor their resting respiratory rate and keep up with regular vet visits. You are your dog's best advocate, and with love and proper care, you can help keep their tail wagging for as long as possible.
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History
Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.
Tue 25 Nov 2025
Edited by Dr Gillian Hill BVSc (Hons)Dr Michelle Wong BVSc
Veterinarian
Dr Michelle graduated from the University of Queensland in 2011 with a Bachelor of Veterinary Science and has worked in small animal practices around South East Queensland. As an owner of three cats, it is not surprising that Dr Michelle holds special interests in feline behaviour and medicine, as well as dermatology and preventative health care. Her favourite part of being a vet is witnessing the special bond between pets and their owners and helping pets live a happy and healthy life.
