By Dr. Becker
Recently, researchers in France set out to learn how common it is for young dogs to have physiological heart murmurs, which are murmurs not associated with a structural abnormality of the heart.
Canine Heart Murmur Study
For the study,1 the scientists evaluated 95 apparently healthy dogs between the ages of 1 and 5 years and across 30 different breeds. Of the 95 dogs, 48 were male and 47 were female, and had a median age of 32 months.
For each dog, cardiac auscultation (listening to heart sounds with the use of a stethoscope) was performed by at least three different examiners: a board-certified veterinary internist, a veterinary cardiology resident, and a veterinary internal medicine resident. The examiners did not compare findings.
Heart murmurs were graded relative to their loudness, as follows:
✓ Grade I
A very soft murmur detected only with effort
✓ Grade II
A soft murmur heard clearly by an experienced examiner
✓ Grade III
A moderately loud murmur that is easily detected
✓ Grade IV
A moderately loud murmur without a thrill (vibration)
✓ Grade V
A loud murmur with thrill that is inaudible when the stethoscope is removed from the chest wall
✓ Grade VI
A very loud murmur with thrill that is still audible after the stethoscope is removed from the chest wall
Dogs discovered to have cardiac arrhythmias or any signs of disease were excluded. Indirect blood pressure measurements were performed to arrive at an average for each dog.
Additional tests included a urinalysis, complete blood count (CBC), and serum chemistry profile, along with an echocardiogram (EKG).
What the Researchers Discovered
Murmurs were noted in 22 of the 95 dogs, or 23 percent. All the murmurs were systolic, were primarily over the left heart base, and ranged between Grade I and Grade III. Additional findings:
- Of the 22 murmurs, 10 were detected only by the board-certified veterinary internist
- In 69 percent of the dogs, all three investigators reported the same findings.
- There were no significant differences in sex, age, body weight, or breed between dogs with murmurs and dogs without murmurs
- 11 of the 22 dogs with murmurs had EKG abnormalities, including mild mitral valve regurgitation (leakage of blood backward through the mitral valve each time the left ventricle contracts), subaortic stenosis, and pulmonary valve stenosis (obstruction of blood flow from the right ventricle to the pulmonary artery)
These results indicate a prevalence of physiological heart murmurs in between 6 and 12 percent (depending on the EKG criteria used) of the 95 dogs in the study, with 27 to 50 percent of the 22 murmurs considered physiological.
The researchers concluded the presence of physiological heart murmurs may extend beyond specific predisposed breeds and growing dogs to a larger population of young, healthy adult dogs.
Unfortunately, Heart Problems in Dogs Are Relatively Common
A heart murmur can be caused by abnormal blood flow within the heart that typically involves one or more heart valves. Murmurs can also be the result when the left and right sides of the heart don't communicate efficiently. A murmur can be congenital (present at birth), or it can develop as the result of disease or the aging process.
When a veterinarian listens to a dog's heart, he or she is evaluating heart rate and rhythm, as well as heart sounds. In a healthy heart, there are just two sounds ("lub-dub"), and they can be clearly heard — they aren't muffled or difficult to pick up. The "lub" is as loud as the "dub," and the rhythm is regular.
The "lub-dub" sound is the result of the heart valves closing as blood flows out of the heart chamber. If a valve doesn't close completely, blood can flow backward into the heart, creating the sound referred to as a murmur.
Causes of Heart Murmurs
Murmurs on the right side of the heart can be caused by tricuspid regurgitation or ventricular septal defect (VSD). Tricuspid regurgitation means the heart's tricuspid valve isn't closing correctly, allowing blood to flow backward into the heart.
A ventricular septal defect (VSD) is a hole or holes in the wall separating the left and right ventricles of the heart. Murmurs on the left side of the heart are most often caused by mitral valve prolapse, stenoses of aortic or pulmonary valves, or patent ductus arteriosus (PDA).
Mitral valve prolapse is a problem with the improper closure of the mitral valve separating the upper and lower chambers of the left side of the heart, and is the most common cause of acquired murmurs in adult dogs.
Stenosis of the aortic or pulmonary valves means the valves have narrowed, causing the heart to work harder to pump blood through the smaller openings. Patent ductus arteriosus (PDA) is a condition in which the ductus arteriosus blood vessel fails to close normally, interrupting the normal blood flow between the aorta and pulmonary arteries that carry blood from the heart.
Heart valve lesions cause murmurs. Congenital (from birth) lesions are much more common in young dogs, while acquired lesions are more often seen in adult dogs.
Symptoms to Watch for and Treatment Options
A few signs to watch for if you suspect or know your pet has a heart problem include:
- Bluish appearing tongue
- Loss of appetite
- Fatigue, weakness, loss of stamina, and decreased exercise endurance
- Too fast or too slow heart beat; increased respiratory effort, including increased respiratory rate
Cardiologists don't actually treat heart murmurs, however, the underlying cause can sometimes be addressed, depending on a variety of factors including the severity of the murmur, the age and health of your dog, the cost of treatment, and other concerns. If possible, I recommend having your dog seen by a board-certified veterinary cardiologist who can provide you with more information about the severity of your pet's heart condition.
I also encourage you to contact a holistic or integrative veterinarian who can partner with you to manage your dog's heart health. I recommend that any pet with a heart issue increase intake of ubiquinol (the reduced form of CoQ10) and omega-3 essential fatty acids, especially krill oil.
I've seen this protocol do an exceptional job slowing down the progression of murmurs, and minimizing the presence of transient murmurs in many patients. Additional beneficial supplements for heart health can include:
- Chinese herbs
- Homeopathic remedies if there are additional symptoms present (shortness of breath, coughing, fatigue with exertion, etc.)
- Amino acids such as taurine, arginine, and acetyl-l-carnitine
- Herbs such as Hawthorne berry and cayenne
- Heart glandulars
Tips to Proactively Protect Your Dog's Heart Health
- Ask your veterinarian for the proBNP blood test. This test can give you peace of mind that your dog has no early signs of heart disease. It's a simple blood test with a fast turn-around time that can provide the information you need to proactively manage your dog's heart health
- Help your dog maintain a good body weight through regular aerobic exercise
- Feed a high quality, balanced, and species-appropriate diet that meets your pet's nutritional requirements for optimal protein (and amino acid) levels, healthy fat, EFA's, and coenzyme Q10, as well as critical micronutrients such as vitamins D and E, calcium, and magnesium, which are often deficient in homemade, unbalanced diets
- Take excellent care of your dog's dental health (bacteria from dirty mouths have been linked to heart valve infections in dogs)