3º Atrioventricular Block (AVB)

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Key Points

Third degree atrioventricular block (3º AVB) is a severe conduction abnormality where no atrial impulses are conducted into the ventricles, resulting in complete atrioventricular dissociation
This dissociation means the ventricles depend on an escape pacemaker to maintain contraction
Most commonly seen in dogs due to age-related or idiopathic degeneration of cardiac tissue
Clinical signs include syncope, collapse, exercise intolerance and sudden death in severe cases
Electrocardiography (ECG) is best for diagnosis and will show no relationship between P waves and QRS complexes
Medical therapy or temporary pacers can be used for stabilisation in the short-term, but definitive treatment requires placement of a permanent pacemaker

Differential Diagnoses

Severe 2º AVB
Atrial standstill
Sick sinus syndrome
Vasovagal syncope

Educational content only. This factsheet is for general veterinary education and is not a substitute for professional veterinary advice, diagnosis, or treatment. Not for use in an emergency — contact a veterinarian or emergency service. Full disclaimer →