heart rhythms

sinus arrhythmia

sinus arrhythmia in dogs

Very common and normal, speeding up with inhale and slowing with exhale.

sinus arrhythmia in cats

Uncommon; usually indicates stress or underlying disease in a clinical setting.

bradycardia

bradycardia in dogs

Can be normal in athletic dogs (e.g., sick sinus syndrome in small breeds) or due to drugs/disease.

bradycardia in cats

Less common; often linked to increased vagal tone or drugs like xylazine.

tachycardia

tachycardia in dogs

Can range from normal (exercise) to pathological (e.g., Boxer cardiomyopathy).

tachycardia in cats

Normal resting rates are high (200+ bpm) and easily elevated by stress, but pathological fast rhythms also occur.

atrial fibrilation (Afib)

atrial fibrilation (Afib) in dogs

More common, usually with severe heart enlargement.

atrial fibrilation (Afib) in cats

rare

ventricular premature contraction

supraventricular premature complexes

premature beats (VPCs/SVPCs) in dogs and ats

Signals originate from ventricles (VPCs) or atria (SVPCs) instead of the SA node; severity varies.

AV blocks

AV blocks in dogs and cats

Signal blockage between atria and ventricles; can range from mild delay (1st degree) to life-threatening complete block (3rd degree)