Hello, caring pet parents! Today, we're tuning into the heart. Sometimes during a routine vet check-up, your vet might mention they hear a "heart murmur." This can sound alarming, but it's important to know that a murmur is not a disease itself. It's a clinical sign. Let's explore what a heart murmur really is and what it might mean for your furry friend.
What is a Heart Murmur?
When your vet listens to your dog's heart with a stethoscope, they should hear a steady "lub-dub, lub-dub" sound. This is the sound of the heart valves closing. A heart murmur is an abnormal "whooshing" or "swishing" sound that's heard in between the normal heartbeats.
This whoosh is caused by turbulent or abnormal blood flow through the heart. Think of it like a smooth-flowing river (normal blood flow) versus a river with rocks in it, creating rapids (turbulent blood flow).
It's important to remember that a murmur is just a sound. It can be a sign of underlying heart disease, but it can also be completely harmless.
The Grading System: How Loud is the Whoosh?
Vets grade heart murmurs on a scale from 1 to 6 to describe their loudness. This grade does not always correlate with the severity of the underlying condition, but it gives vets a way to describe and track the murmur.
- •Grade 1: Very, very soft. You can only hear it in a quiet room after listening for a while.
- •Grade 2: Soft, but easily heard with a stethoscope.
- •Grade 3: Moderately loud.
- •Grade 4: Loud. You can also feel a "thrill" (a vibration) when you put your hand on the dog's chest.
- •Grade 5: Very loud. Can be heard with the stethoscope just barely touching the chest.
- •Grade 6: Extremely loud. Can be heard with the stethoscope held just off the chest wall.
What Causes a Heart Murmur?
There are many potential causes of a heart murmur, ranging from harmless to serious.
"Innocent" or "Physiologic" Murmurs:
- •Puppies: It's quite common for young puppies to have a soft, "innocent" murmur that they grow out of by the time they are 4-6 months old.
- •Anemia, Fever, or Excitement: Conditions that change the thickness of the blood or increase the heart rate can cause a temporary murmur.
Murmurs Caused by Heart Disease:
This is the more serious category. The murmur is a sign that there is a structural problem with the heart.
- •Leaky Heart Valves: This is the most common cause of murmurs in adult dogs. Conditions like Mitral Valve Disease cause the heart valves to become thick and leaky, allowing blood to flow backward, which creates the whooshing sound.
- •Narrowed Valves (Stenosis): A valve may be too narrow, forcing blood to squirt through a smaller opening. This is common in conditions like Pulmonic Stenosis or Aortic Stenosis.
- •Holes in the Heart (Septal Defects): Some dogs are born with a hole between the chambers of their heart (like an atrial or ventricular septal defect), which allows blood to flow abnormally.
- •Dilated Cardiomyopathy (DCM): In this disease of the heart muscle, the heart becomes a weak and inefficient pump, which can sometimes cause a murmur.
- •Heartworm Disease: Can also cause murmurs.
What Happens After a Murmur is Found?
If your vet hears a murmur, the next steps depend on the grade of the murmur, your dog's age and breed, and whether they are showing any other signs of illness.
- •For a soft murmur in a healthy puppy: Your vet may just recommend monitoring it to make sure it goes away as they grow.
- •For a new murmur in an adult dog, or a loud murmur: Your vet will recommend further diagnostics to figure out the cause.
The Diagnostic Toolkit:
- •Chest X-rays: These are great for seeing the overall size and shape of the heart and checking for fluid in the lungs (a sign of heart failure).
- •Echocardiogram (An Ultrasound of the Heart): This is the most important test! An echo allows a veterinary cardiologist to look at the heart in real-time. They can see the heart valves, measure the heart chambers, and watch the blood flow. This is the test that will tell you exactly what is causing the murmur and how severe the problem is.
- •Electrocardiogram (ECG or EKG): This measures the electrical activity of the heart and is used to detect any arrhythmias (abnormal heart rhythms).
- •Blood Pressure: High blood pressure can be related to heart disease.
Living with a Heart Murmur
The prognosis for a dog with a heart murmur depends entirely on the underlying cause.
- •An innocent puppy murmur has an excellent prognosis.
- •A murmur due to severe heart disease may require lifelong medication and monitoring.
The key takeaway is not to panic if your vet hears a murmur. It's a starting point for a conversation and potentially a diagnostic workup. By working with your vet and a veterinary cardiologist, you can get a clear diagnosis and create the best possible plan to keep your dog's heart as healthy as possible for as long as possible.
Sources & Further Reading:
- •VCA Animal Hospitals - Heart Murmurs in Dogs
- 1American Kennel Club Canine Health Foundation - Understanding Heart Murmurs in Dogs