What is a Heart Murmur?

A heart murmur is an abnormal sound heard during a veterinary examination when listening to your dog's heart with a stethoscope. It is caused by turbulent blood flow within the heart or blood vessels. While heart murmurs themselves are not a specific diagnosis, they indicate an underlying issue with the heart's structure or function.

Causes of Heart Murmurs

•      · Congenital heart defects: Some dogs are born with abnormalities in the structure of their hearts, such as defective heart valves or holes in the heart walls.

•      · Acquired heart disease: Ageing, infections, heartworm disease, or other conditions can lead to changes in the heart's function and the development of murmurs. The most common cause of acquired heart disease is Mitral Valve Insufficiency (or mitral regurgitation) where the mitral valve becomes diseased, thickened and leaky.

•      · Other health issues: Conditions like anaemia or hyperthyroidism can also contribute to the development of heart murmurs.

Grading of Heart Murmurs

Heart murmurs are graded based on their intensity, with Grade I being the mildest and Grade VI being the most severe. The grading system helps veterinarians assess the severity of the murmur and its potential impact on your dog's health. The severity of the heart murmur does not always correlate with the severity of the heart disease.

•      · Grade I: Barely audible, heard only under ideal conditions.

•      · Grade II: Soft but readily audible with a stethoscope.

•      · Grade III: Moderately loud and easily heard with a stethoscope.

•      · Grade IV: Loud and accompanied by palpable vibrations (thrills) on the chest wall.

•      · Grade V: Very loud with a palpable thrill, often indicating severe heart disease.

•      · Grade VI: Loudest, often heard even without a stethoscope, and associated with significant heart disease.

Diagnosis of Heart Murmurs

To determine the underlying cause and severity of your dog's heart murmur, your veterinarian may recommend the following diagnostic tests:

•    · Physical examination: Including auscultation (listening to the heart with a stethoscope) to determine the grade and characteristics of the murmur.

•    · Blood testing: Blood testing can help to determine whether there are any primary conditions within your pets body that may be contributing to the heart murmur. A hormone called Pro-BNP can also be tested. This is a hormone specific to the heart which is produced in response to heart muscle stretching and can be used to diagnose and monitor heart disease.

•    · Chest X-rays: To assess the size and shape of the heart and detect any signs of heart enlargement or fluid accumulation in the lungs.

•    · Echocardiography (ultrasound of the heart): Provides detailed images of the heart's structure and function, allowing for the diagnosis of specific cardiac conditions.

•    · Electrocardiography (ECG): Measures the electrical activity of the heart and can help detect arrhythmias or abnormalities in heart rhythm.

Treatment of Heart Murmurs

Treatment for heart murmurs in dogs depends on the underlying cause, severity of the condition, and presence of associated symptoms. A holistic approach is necessary to manage the multiple factors which may be associated with heart disease. Treatment options may include:

•    · Medications: Such as diuretics, ACE inhibitors, beta-blockers, or pimobendan to manage symptoms, improve heart function, or address underlying issues.

•    · Dietary management: Prescription diets formulated to support cardiac health and manage specific conditions, such as heart failure or high blood pressure.

•    · Lifestyle modifications: Maintaining a healthy weight, providing regular exercise, and avoiding activities that may exacerbate symptoms (e.g., excessive exertion or stress).

•    · Surgery may be an option for some congenital heart disease. Diseases where surgery may be an option include pulmonic stenosis and patent ductus arteriosus.

•    · Regular monitoring: Follow-up examinations and diagnostic tests to track your dog's cardiac health and adjust treatment as needed

Innocent or Physiologic Heart Murmurs

An innocent heart murmur, also known as a benign or physiological heart murmur, is a type of heart murmur commonly found in puppies and young dogs. Unlike pathological heart murmurs, which are often associated with underlying cardiac abnormalities or diseases, innocent heart murmurs typically occur in otherwise healthy puppies and are not indicative of any significant cardiac issues. Innocent murmurs are usually soft, grade I or II murmurs that are heard intermittently during a veterinary examination. They are caused by turbulent blood flow within the heart or blood vessels and are considered harmless and benign. These murmurs may first appear as a young puppy, at approximately 6-8 weeks, and they will usually resolve or disappear by 4-5 months of age. It's important to note that innocent heart murmurs do not require treatment and typically do not cause any clinical signs or health problems in affected puppies. However, it's essential for puppies with heart murmurs to undergo regular veterinary check-ups to monitor their cardiac health and ensure that the murmur remains innocent.