It is not uncommon for dogs (or human children for that matter) to have growth-related heart murmurs that are benign, called “innocent” murmurs. A heart murmur is not a diagnosis of something but rather a potential symptom. This means that a heart murmur does not indicate anything other than that the heart did not sound correct when listened too. Heart murmurs are graded on a scale of 1-6 in order of loudness. A heart murmur is an irregular sound in the heart beat- instead of a “Lub-dub”, there can be a whooshing sound. Some heart murmurs are ‘transient’ meaning they go away and some remain. Heart murmurs that remain but are not indicative of any underlying medical condition are referred to as innocent murmurs. There are a myriad of reasons for a heart murmur may be heard. Developmental- this just means that the heart murmur is a normal part of development and is often the case in growing kids and puppies. However, a murmur that does not resolve (go away on its own) may indicate an underlying problem. Some of the more common causes of heart murmurs:
– a valve not closing properly
– stenosis (narrowing- often in this breed, narrowing after the aortic valve called subaortic stenosis or SAS)
– dehydration
– pregnancy- (I had a heart murmur when I was pregnant with my children child).
– stress/anxiety/nervous
Thus, a heart murmur in and of itself does not always signify a problem, but it does let you know it needs to be monitored to see if it goes away or not or if it progresses. Loudness (1-6) likewise is also not always indicative of severity.
- Grade 1: This is a very soft and quiet murmur that is almost undetectable.
- Grade 2: This is a soft murmur that can be easily heard by a vet.
- Grade 3: This is a low to moderate noise.
- Grade 4: This is a moderate to loud noise.
- Grade 5: This will be loud enough to make your dog’s chest vibrate.
- Grade 6: This can be heard by listening directly on the chest wall.
https://www.webmd.com/heart-disease/heart-murmur-symptoms
Some important take-aways from the previously linked article:
A healthy heart makes a “lub-dub” sound as it beats. The “lub” (systolic sound) happens when part of the heart contracts, and the mitral and tricuspid valves close. The “dub” (diastolic sound) occurs when part of the heart relaxes, and the aortic and pulmonic valves close. A heart murmur is an extra sound in the heartbeat — such as a ”whooshing” — that is caused by turbulent blood flow through the heart valves.
Heart murmur sounds
A normal heartbeat makes a lub-dub sound. When you have a heart murmur, your doctor will hear a whooshing or humming sound between beats. The abnormal flow of blood through your heart valves causes this sound.
The volume of a heart murmur doesn’t always relate to how severe it is. A loud murmur may not be more severe than a quiet one. The type of murmur is a sign of its severity, though. Systolic heart murmurs are often innocent, or harmless.
How serious is a heart murmur?
A heart murmur itself isn’t dangerous. Some heart murmurs don’t cause any problems. Others are signs of a serious heart condition.
Thankfully, I have not had very many “non-innocent” heart murmurs over the years that did not go away as the pup grew. I would like to hope that it is because of all of the genetic and health screens we do, including always hearts, and how carefully I choose the bloodlines to use, however, having so few means I also do not have a ton of hands-on experience. I have had 3 instances where the murmur turned out to be a heart defect.
The first is a grade 6 we had that was later downgraded to a 4, then a 3, then an intermittent 1 as he grew. I adopted this particular puppy, named Tuck, out to the bishop of our church before they moved to Florida. Tuck is about 6 years old now and they always bring him back up to Indiana when they come to visit. He is MASSIVE- 140 pounds! But such a lovable bear and great with all 9 (yes, NINE!) of their kids.
One other heart murmur I had was one of Hex’ kids a few years ago. He was a 5/6, and the family that co-owns Hex wanted to adopt him and keep him. They did an echocardiogram on him and it turned out he had aortic stenosis (narrowing of the aerobic valve opening). The cardio vet told them that after he was done growing, he may need to have what is called valvuloplasty. This is where a balloon is inserted down through the jugular and into the valve that is narrowed. The balloon is then inflated to increase/stretch the opening. Thank goodness, he did not end up needing that surgery as his heart grew as he did, and now he just has annual check-ups.
Lastly, there was my Diesel. We did not discover his heart murmur until he was older and he was diagnosed with SAS or subaortic stenosis. Dr. Udrasols told us that at some point in the future, he might also need to have a valvuloplasty, but, thankfully, he also never needed that and lived to be 15+ years old and ran faster and harder than dogs much younger than him when he was already double digits. He cart-pulled, did bite work, walked in parades and lived life to the fullest.
By God’s good grace (knock on wood) that is the extent of my interaction with heart murmurs, but I also do not want to downplay them. I do want to emphasize that this has been my experience only and is not representative of how it will always turn out as there are many things that can cause a heart murmur- some totally benign, and some that will need medical intervention. Those situations were very fortunate as were all of mine that turned out to be innocent, but I know that is not always the case. They can be an indication of something wrong- something that may require medical intervention down the road, or may even require heart medication. I do not have any experience with either, so I cannot tell you any personal experience in that area.
Here is another link that I thought did a good job of explaining it in plain terms:
https://vcahospitals.com/know-your-pet/heart-murmurs-in-dogs
Some take-aways from the previously linked study:
What is an innocent or physiologic heart murmur?
An innocent or physiologic heart murmur is a heart murmur that has no impact on the dog’s health. It is very common for young puppies, especially large breed puppies, to develop an innocent heart murmur while they are growing rapidly. The murmur may first appear at 6-8 weeks of age, and a puppy with an innocent heart murmur will usually outgrow it by about 4-5 months of age. This type of murmur is benign (not harmful). In general, a physiologic or innocent heart murmur will have a low intensity (usually Grade I-II out of VI) and does not cause any symptoms or clinical signs.
A dog with a heart murmur that is caused by a structural heart disease or an extracardiac problem will generally have some symptoms or clinical signs that can be attributed to the disease. The most common symptoms are poor appetite, weight loss (or stunted growth in a puppy), breathing problems (often occurring in the middle of the night or after the dog has been lying down for a period of time), poor exercise tolerance, collapse or fainting spells, pale gums, and coughing.
