Hi stranger! Signing up for MypetMD is easy, free and puts the most relevant content at your fingertips.

Get Instant Access To

  • 24/7 alerts for pet-related recalls

  • Your own library of articles, blogs, and favorite pet names

  • Tools designed to keep your pets happy and healthy

or Connect with Facebook

By joining petMD, you agree to the Privacy Policy.

PetMD Seal

Heart Block or Conduction Delay (Right Bundle) in Dogs


Right Bundle Branch Block (RBBB) in Dogs


Right Bundle Branch Block (RBBB) is a defect in the heart’s electrical conduction system in which the right ventricle (one of the dog's four heart chambers) is not directly activated by the electric impulses through the right bundle branch. RBBB may be complete or partial in nature.


Symptoms and Types


Often, no specific symptoms are seen that can be attributed to RBB, only those that are related to the underlying disease causing the defect.




Although it may be present in normal dogs, a right bundle branch block is more often associated with congenital (present at birth) heart disease(s). Other typical causes for the defect include:


  • Chronic valve disease with fibrosis
  • Heart surgery to correct cardiac defect
  • Injury involving heart
  • Tumor(s)
  • Parasitic infection (e.g., heartworms)
  • Cardiomyopathy
  • Formation of clot in blood vessel (thromboembolism)
  • Abnormally high levels of potassium (hyperkalemia)




You will need to give a thorough history of your dog’s health, including the onset and nature of the symptoms, to the veterinarian. He or she will then perform a complete physical examination, as well a biochemistry profile, urinalysis, and complete blood count (CBC) -- the results of which are typically non-specific. However, biochemistry profile may show high levels of potassium.


RBBB is often only found accidentally, perhaps while performing an echocardiogram. In the case of this defect, he or she may identify structural defects in the heart and right-side enlargement. Thoracic and abdominal radiography, meanwhile, may show masses and other abnormalities. If heartworms are the underlying cause, they also may be identified in diagnostic procedures.




Related Articles

Excess Sodium in the Blood in Dogs

The term hypernatremia means higher than normal concentrations of sodium in blood. Such elevations are commonly seen in abundant loss of water...

Low Blood Oxygen in Dogs

When the brain is deprived of oxygen, irreversible damage may be the result, even when the deprivation has been for a short period of time.

Congenital Heart Defect (Ebstein’s Anomaly) in Dogs

Ebstein's anomaly is the medical name given to a type of congenital heart defect in which the opening of the tricuspid valve (on the right side...

Heart Block (Mobitz Type II) in Dogs

Second degree AV block in dogs is a disease in which the electrical conduction system goes off course, as some impulses are not passed down from...