Murmurs are additional heartbeats that occur because of a disturbance in the blood flow that is strong enough to be found with an auditory diagnosis (i.e. listening). Various characteristics are often used to classify heart murmurs - for example, systolic murmurs happen during the heart muscle's contraction, diastolic murmurs occur during the moments the heart muscle relaxes between pumps, and continuous/to-and-fro murmurs happen during almost all of the heartbeat's process.
Types of Heart Murmurs & Symptoms in Dogs
The symptoms associated with murmurs depend on various characteristics, including their location, grade, and configuration. However, if the murmur is associated with structural heart disease, your dog might exhibit signs of congestive heart failure such as coughing, weakness, or exercise intolerance.
Some common symptoms of heart diseases and disorders include:
- Lack of energy or appetite
- Irregular heartbeat or racing pulse
- Gums and/or tongue are bluish in color
- Excessive panting even when resting
- Hacking, persistent cough
- Severe water retention
- Collapsing or fainting
The Causes of Heart Murmurs in Dogs
Heart murmurs in dogs can be caused by some of these problems:
- Blood flow disturbance related to backflow due to a compromised or dysfunctional valve, patent ductus arteriosus, or a defect in the heart's wall.
- Blood flow disturbance related to obstruction or diseased valves
- Blood flow disturbance related to high flow/unusual structural vibrations
Heart murmurs can be caused by specific illnesses and conditions, such as the following:
Systolic Heart Murmurs
- Heartworm disease
- Mitral and tricuspid valve endocarditis (inflammation of the inner heart)
- Aortic stenosis
- Dynamic right ventricular outflow obstruction
- Atrial and ventricular septal defect
- Mitral and tricuspid valve dysplasia
- Cardiomyopathy and aortic valve deficiency
- Tetralogy of Fallot
- Pulmonic stenosis
- Dynamic subaortic stenosis
- Systolic anterior mitral motion (SAM)
- Mitral and tricuspid valve heart failure
Continuous or To-and-Fro Heart Murmurs
- Aortic stenosis with aortic regurgitation
- Ventricular septal defect with aortic regurgitation
- Patent ductus arteriosus
Diastolic Heart Murmurs
- Aortic and pulmonic valve endocarditis (inflammation of the inner layer of the heart)
- Mitral and tricuspid valve stenosis
Diagnosing Heart Murmurs Diagnosed in Dogs
Your veterinarian can tell the difference between a large number of abnormal heart sounds including split sounds, gallop rhythms, clicks, and ejection sounds. In addition to this, they must be able to differentiate between abnormal heart and lung sounds and identify any relationship between the timing of the sound and either breathing or heartbeat.
Your vet might also recommend additional diagnostic testing such as X-rays of your dog's chest, complete blood count, and echocardiography.
The Grading Scale for Dog Heart Murmurs
Grade I: So quiet it can hardly be heard
Grade II: Quiet, but can be heard with a stethoscope
Grade III: Medium-loud, usually related to mechanical blood circulation problems
Grade IV: Loud, able to 'echo' widely, including both sides of the chest
Grade V: Very loud, a vet can hear it with a stethoscope barely touching the chest; it can also be physically felt through the dog's chest
Grade VI: Very loud, the murmur is audible with a stethoscope barely on the dog's chest; the vibration is strong enough to be felt through the chest
Treating Heart Murmurs In Dogs
Thankfully, unless your dog is or has a chance of going into heart failure, their condition is most likely treatable on an outpatient basis. However, some dogs (e.g. puppies with a low-grade heart murmur) need little to no treatment, it is recommended to monitor the dog's health on an ongoing basis with routine diagnostic imaging.
A heart murmur caused by cardiac disease or defect may require medication, a specialized diet, or surgery. At the very minimum, your dog will require vet visits every 6 months to monitor the murmur. This visit may require a repeat echogram and/or X-rays depending on your dog's condition.
Your veterinarian or specialist will develop and explain to you the best possible treatment and monitoring plan for your pup's condition.
Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.