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Heart Block or Conduction Delay (Right Bundle) in Dogs

Right Bundle Branch Block (RBBB) in Dogs

Right Bundle Branch Block (RBBB) is a condition affecting the heart’s electrical conduction system, wherein the right ventricle, one of the four heart chambers in dogs, does not receive direct electrical impulses through the right bundle branch. RBBB can manifest as complete or partial blockage.

Symptoms and Types

Typically, there are no distinct symptoms directly associated with RBBB; any observable symptoms are usually linked to the underlying condition responsible for the defect.


While it can occur in healthy dogs, a right bundle branch block is commonly linked to congenital heart diseases present from birth. Other usual causes for the defect include:

  • Chronic valve disease leading to fibrosis
  • Cardiac surgery to address heart defects
  • Heart-related injuries
  • Presence of tumor(s)
  • Infection by parasites such as heartworms
  • Cardiomyopathy
  • Formation of blood clots in vessels (thromboembolism)
  • Excessive levels of potassium in the bloodstream (hyperkalemia)


When consulting the veterinarian, it’s essential to provide a detailed history of your dog’s health, including when symptoms first appeared and their nature. The veterinarian will conduct a thorough physical examination along with various tests including a biochemistry profile, urinalysis, and complete blood count (CBC). While these tests may not specifically indicate RBBB, elevated potassium levels might be observed in the biochemistry profile.

RBBB is often incidentally discovered, possibly during an echocardiogram. During this examination, structural heart defects and enlargement on the right side may be identified. Additionally, thoracic and abdominal radiography might reveal masses or other irregularities. If heartworms are suspected as the underlying cause, diagnostic procedures may confirm their presence.


Therapeutic measures focus on addressing the underlying cause.

Living and Management

RBBB alone does not pose a significant threat to life, and resolving the underlying cause typically resolves the issue completely. However, if left untreated, RBBB can progress to more serious heart rhythm disturbances or even complete heart block.

Regular follow-up examinations may be necessary to assess the progression of the disease and your dog’s response to treatment. No dietary changes are typically needed unless specifically recommended to manage the underlying condition.

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