Page 165 - Problem-Based Feline Medicine

10. The cat with tachycardia, bradycardia

or an irregular rhythm

Luis A H Braz-Ruivo, Kathy A Arrington and Fiona

Campbell

KEY SIGNS
● Tachycardia.
● Bradycardia.
● Irregular heart sounds or pulse.

MECHANISM?
● Arrhythmias are caused by two basic abnormalities: disorders of impulse formation and disor-
ders of impulse conduction.
● Alterations of impulse formation are usually the result of diseased myocardial cells.
● Alterations of electrical impulse conduction occur secondary to primary diseases of the con-
duction system.

WHERE?
● Arrhythmias can occur wherever there is excitable cardiac tissue in the heart.
WHAT?
● Most cats with a cardiac arrhythmia are asymptomatic.
● The most common arrhythmia is ventricular premature contractions (VPCs).

QUICK REFERENCE SUMMARY

Diseases causing tachycardia, bradycardia or an irregular rhythm
TACHYARRHYTHMIAS
ANOMALY
● Ventricular pre-excitation
This is a rare cardiac arrhythmia resulting from the presence of a congenital bundle of muscle across the
atrioventricular annulus – allowing bypass of the electrical impulse to the ventricles.
It can occur at any age; in many cases, it is an incidental finding. The most common symptom is
syncope or lethargy during the periods of supraventricular tachycardia.

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