Isorhythmic atrioventricular dissociation in a Shih-tzu dog

Authors: Beluque T, Endrighi M, Vila BCP, Costa BN, Sousa MG
Publication: Australian Veterinary Practitioner, Volume 54, Issue 2, pp 77-82, Jun 2024
Publisher: Australian Veterinary Association

Animal type: Dog
Article class: Clinical Article

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Abstract:

Isorhythmic atrioventricular dissociation (IAVD) is a conduction disorder between the atria and ventricles in which both a sinus rhythm and a separate rhythm originating in the atrioventricular junction or ventricular myocardium coexist. The P waves and QRS complexes are dissociated and can be classified as type I and type II synchronisation patterns. This study describes electrocardiographic findings from a Shih-tzu dog with IAVD with type I synchronisation, characterised by the fluctuation of P waves in relation to the QRS complexes. This condition was associated with heart disease, namely mitral valve disease and pulmonary hypertension. The animal did not require treatment with antiarrhythmic drugs. Structural heart disease and its implications may have contributed to the development of this arrhythmia.

Keywords: arrhythmia, myxomatous mitral valve disease, electrocardiography, pulmonary hypertension

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