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Heart Block or Conduction Delay (Left Anterior) in Dogs

Left Anterior Fascicular Block in Dogs

Left Anterior Fascicular Block (LAFB) in dogs is a cardiac issue arising from an irregular conduction system, which regulates the generation and propagation of electrical impulses across the heart muscles. These impulses trigger contractions essential for pumping blood throughout the body. When the conduction system malfunctions, it disrupts both the heart muscle contractions and the rhythm of heartbeats. Thankfully, this condition is rare among canine patients.

Symptoms and Types

Symptoms associated with Left Anterior Fascicular Block (LAFB) are not specific to the condition itself but rather indicative of the underlying cause of LAFB.


Causes of Left Anterior Fascicular Block (LAFB) include heart surgery, electrolyte imbalances, and various heart conditions such as ischemic cardiomyopathy, ventricular septal defect, and aortic valvular disease.


For diagnosis, your veterinarian will begin by gathering a detailed history of your dog’s health, including the onset and characteristics of symptoms. A comprehensive physical examination will be conducted, along with biochemical profiling, urinalysis, and complete blood count (CBC) to identify potential electrolyte imbalances.

Electrocardiography (ECG) stands as a primary diagnostic tool, where your veterinarian will analyze your dog’s ECG alongside a standard ECG to detect abnormalities. Echocardiography is typically performed for further assessment of heart function and to diagnose any underlying heart conditions and their severity.

Additionally, X-rays of the thoracic and abdominal regions will be taken to evaluate the presence of abnormal masses, tumors, foreign bodies, or any irregularities in heart position.


The treatment approach for your dog will largely depend on the specific diagnosis and may differ from one patient to another. Hence, accurately identifying the underlying cause of the LAFB is crucial for determining the appropriate course of treatment.

Living and Management

The prognosis and frequency of follow-up examinations greatly vary based on the underlying disease. In instances of severe or advanced heart conditions or cancer, the prognosis is typically poor. It’s essential to consult with your dog’s veterinarian in all cases.

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