Diseases and Conditions: How to Handle Heart Murmurs in Dogs

Heart murmurs are abnormal sounds that veterinarians can detect while listening to a dog's heart with a stethoscope. These murmurs deviate from the normal "lub-dub" rhythm and can have a "shooshing" or "whooshing" quality. Murmurs occur between familiar heart sounds and often indicate turbulent blood flow.

Causes of Heart Murmurs

Turbulent blood flow, similar to rapids in a river, causes heart murmurs. The heart's anatomy and function play a significant role in this turbulence. Blood flows through the heart's chambers and valves, and any disruption, malfunction, or structural abnormality can create turbulence and result in a murmur. Common causes include:

  1. Valve Malfunction: Leaky or malfunctioning heart valves, like the mitral valve, can lead to backflow and turbulence.
  2. Holes in the Heart: Abnormal connections between chambers or arteries can disturb normal blood flow.
  3. Narrowing of Vessels: Constricted vessels create turbulence as blood is squeezed through.
  4. Vibrating Structures: Structures within the heart can vibrate as blood flows past, causing murmurs.
  5. Thinner Blood: Anemia or excitement can lead to thin blood, contributing to murmurs.

Types of Murmurs and Associated Conditions

Murmurs can provide clues about the underlying condition based on their timing, location, and quality. For instance:

  • Degenerative Mitral Valve Disease: Common in older dogs, these murmurs are usually heard on the lower left of the chest.
  • Patent Ductus Arteriosus: Continuous murmurs near the left armpit indicate this condition.
  • Aortic Stenosis: Murmurs may radiate up the carotid arteries and be heard over the neck.
  • Ventricular Septal Defects: Loudest on the right side, these murmurs indicate holes between chambers.

However, diagnosis based solely on murmur characteristics can be challenging.

Benign Murmurs and Congenital vs. Acquired Murmurs

  • Benign Murmurs: Some murmurs are considered benign, occurring in puppies or anemic/excited animals. Benign puppy murmurs usually disappear by 12-15 weeks.
  • Congenital Murmurs: Present from birth, these indicate heart defects. Acquired murmurs develop later in life and are often linked to heart disease.

Grading and Assessment of Murmurs

Veterinarians grade murmurs on a scale from 1 to 6, indicating their loudness. However, grading can be subjective and may not directly correlate with the severity of the underlying issue. Murmurs can be described as soft, moderate, loud, or palpable (vibrating). The grade helps communicate the murmur's characteristics to other professionals.

Actions to Take

  • Dogs: Based on age, breed, history, and physical exam, a veterinarian may diagnose the origin of the murmur. Further testing, such as radiographs or an echocardiogram, may be recommended for confirmation.


Treatment targets the underlying cause of the murmur. Depending on factors like severity, age, and overall health, options may include medical management, surgery, or specialized care.

In summary, understanding heart murmurs involves identifying the underlying causes through careful examination, diagnostic tests, and collaboration between pet owners and veterinarians. Proper diagnosis and appropriate treatment help ensure the well-being of your furry friend.

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