A Pet Owner’s Guide to Heart Disease in Dogs
Hearing your veterinarian say “heart disease” is one of the moments every dog owner dreads. The words are heavy and immediately fill your mind with worry. Will they be okay? How long do they have? What did I do wrong?
First, take a deep breath. A diagnosis of heart disease in dogs is not an immediate endpoint.
As veterinary professionals, we understand that fear. But the most important thing to know is that advances in veterinary cardiology have completely changed how we manage these conditions. Today, many dogs with heart disease live long, happy, and comfortable lives.
The key is early detection, accurate diagnosis, and a dedicated management plan.
This post will walk you through the signs of heart disease in dogs, the common causes, the different stages, and the treatment options that a specialist can provide.
Learn more about the MVA Family of Hospitals Cardiology service.
What Is Heart Disease in Dogs?
It’s helpful to know that “heart disease” isn’t a single condition. It’s an umbrella term for any abnormality of the heart. The heart is a complex, four-chambered muscle that acts as a powerful pump. Its job is to pump oxygenated blood to the entire body and send deoxygenated blood to the lungs. Heart disease occurs when any part of this system—the valves, the muscle, the electrical rhythm, or the surrounding sac—stops working correctly.
These conditions generally fall into two categories:
- Congenital: Meaning that the dog was born with a heart defect.
- Acquired: This means the disease developed over time due to wear-and-tear, infection, or other factors. This is, by far, the most common type we see.
Common Causes of Heart Disease in Dogs
While some breeds are genetically predisposed, several conditions are common culprits:
- Myxomatous Mitral Valve Disease (MMVD): This is the most common acquired heart disease in dogs. It’s a progressive condition where the heart’s mitral valve (between the left atrium and ventricle) degenerates, thickens and “leaks”, causing blood to back flow This is especially common in small to medium-sized older dogs, like Cavalier King Charles Spaniels, Dachshunds, and Poodles.
- Dilated Cardiomyopathy (DCM): This is disease where the heart muscle becomes thin, weak, and enlarged, making it unable to pump blood effectively. We see this most often in large and giant breeds, such as Doberman Pinschers, Great Danes, and Irish Wolfhounds.
- Heartworm Disease: This is a tragic and entirely preventable cause of heart disease. Mosquitoes transmit parasitic worms that live in the heart and major blood vessels, causing severe damage to the heart and lungs. Year-round once monthly preventative heartworm medication prevents this from occurring.
- Arrhythmias: These are electrical disturbances that cause the heart to beat too fast, too slow, or with an irregular rhythm. There are several potential inciting causes of this condition.
The Most Important Part: Signs of Heart Disease in Dogs
This is where you, as an owner, are the most important part of the care team. The earliest signs of heart disease in dogs are often subtle and easy to miss.
In the early stages, your dog may have no signs at all. A heart murmur (an abnormal whooshing sound your vet hears with a stethoscope) is often the only clue that something is wrong.
This is why your dog’s annual check-up is so critical. As the disease progresses, the heart struggles to compensate. When it can no longer keep up, you may start to see signs of Congestive Heart Failure (CHF). This is when fluid “backs up” into the lungs or abdomen.
Watch for these signs, especially in senior dogs:
- A new, persistent cough, especially at night, when lying down, or after excitement/exercise. This is often described as a “soft” cough.
- Exercise intolerance: Tiring out more quickly on walks, being less playful, or lagging behind.
- Increase in resting respiratory rate: Count the number of breaths your pet takes in 1 minute when they are asleep (it is important they are not active, or interacting with you when you count them). Typical breath rates should not exceed ~32 respirations per minute; make a visit with your veterinarian if you are noting mild elevations. Seek emergency care if there is significant increases.
- Difficulty breathing (dyspnea): This can look like rapid, shallow breaths, or even severely panting when at rest. This often indicates that your pet is currently experiencing heart failure – this is a medical emergency.
- Restlessness: Pacing, seeming unable to get comfortable, or choosing to sleep sitting up instead of lying down.
- Fainting (syncope) or collapsing: This is a serious sign that warrants an immediate veterinary visit.
- A distended abdomen: This “pot-belly” appearance can be a sign of fluid buildup (called ascites).
- Pale or blue-tinged gums: This is a medical emergency.
If you notice any of these signs, it’s time to see your veterinarian.
Diagnosis & Treatment for Heart Disease in Dogs
The first step your veterinarian will take is to listen with a stethoscope. If they hear a murmur, arrhythmia, or muffled heart sounds, they will recommend further diagnostics.
While X-rays and bloodwork are essential, the “gold standard” for diagnosing heart disease is an echocardiogram (an ultrasound of the heart), occasionally in combination with an electrocardiogram (ECG).
This is where a specialist comes in.
A Board-Certified Veterinary Cardiologist is a veterinarian who has undergone years of intensive, advanced training specifically in heart and respiratory diseases. They are the experts who perform and interpret these complex tests.
An echocardiogram is an ultrasound of the heart. It is a non-invasive, painless test that allows the cardiologist to watch the heart pump in real-time. They can see the valves opening and closing, measure the heart muscle’s thickness, and assess how well it’s functioning. This is the only test that can definitively diagnose the specific type of heart disease, determine its severity, and accurately stage it.
Based on these findings, the cardiologist will create a tailored treatment plan. For most acquired heart disease, the goal is not a “cure.” The goal is to:
- Slow the progression of the disease.
- Manage the signs.
- Provide the best possible quality of life for as long as possible.
Treatment almost always involves oral medications. These may include:
- Diuretics (like Furosemide): To help clear fluid from the lungs.
- ACE Inhibitors (like Enalapril): To reduce pressure on the heart.
- Pimobendan (Vetmedin): A vital medication that helps the heart muscle contract more efficiently and opens up blood vessels.
- Anti-arrhythmic drugs: To control an abnormal heart rhythm.
Schedule an appointment with a Board-Certified Veterinary Cardiologist.
Understanding the Staging of MMVD in Dogs
If your pup is found to have MMVD or DCM, a “stage” will be assigned to your dog’s heart disease to be determine treatment and prognosis. For MMVD, we use the ACVIM (American College of Veterinary Internal Medicine) system, which is broken down simply:
- Stage A: The “at-risk” stage. This includes dogs from breeds with a high genetic risk (like Cavaliers) but who currently have no signs of heart disease.
- Stage B: The disease is present, but there are no clinical signs (no coughing, etc.). A murmur is detectable.
- Stage B1: Heart murmur is present, but X-rays and/or an echocardiogram show the heart is not
- Stage B2: Heart murmur is present, and there is clear evidence of heart enlargement. This is a critical stage, as studies show that starting certain medications now can significantly delay the onset of heart failure.
- Stage C: The dog is in or has been in Congestive Heart Failure (CHF). This is when dogs are showing clinical signs like coughing or difficulty breathing. This is sometimes when many owners first realize there’s a problem. Immediate treatment in addition to long term medications are needed.
- Stage D: The dog is in advanced heart failure that is no longer responding to standard treatments.
The MVA Difference: Specialist-Led Cardiology
When your primary care veterinarian refers you to the Cardiology department at Metropolitan Veterinary Associates (MVA), Hickory Veterinary and Specialty Hospital (HVSH), or Metropolitan Veterinary Urgent Care & Specialty (MVUCS), you are getting a level of care that goes beyond the standard.
Our team is led by board-certified cardiologists who use state-of-the-art diagnostic equipment. We work in partnership with your family veterinarian to create a complete, 360-degree care plan for your dog.
A diagnosis of heart disease is scary. But with the right team, it is a manageable condition. Early diagnosis, specialist-led care, and consistent monitoring can give you and your beloved companion many more months, or even years, of quality time together.
If you have concerns about your dog’s heart health, or if your veterinarian has detected a murmur, don’t wait. Ask for a referral to a veterinary cardiologist and schedule an appointment today.