Atrial Standstill

Introduction

The temporary or permanent lack of atrial activity resulting from a failure of atrial depolarisation. The ventricles still function normally.

Aetiology

The atrial muscle fails to depolarise, despite the production of an impulse from the sinoatrial node. So instead impulses pass from the sinoatrial node to the atrioventricular node by internodal pathways. This produces a sinoventricular rhythm. This can be caused by electrolyte abnormalities (especially hyperkalaemia), cardiomyopathies, muscular dystrophy, hypoadrenocorticism and toxicity.

Clinical Signs

Heart sounds are normal on auscultation. As ventricular depolarisation occurs a normal pulse can be felt. It is common for the heart rate to be slow, at less than 60 beats a minute in small animals.

Diagnosis

Diagnosis can be confirmed by ECG or fluoroscopy.

ECG

An ECG should show an absence of P waves. Heart rate is regular but normally slow, due to the presence of an escape rhythm. The QRS complexes are normal or slightly wide.

It is important to have an artefact-free ECG of diagnostic quality to confirm atrial standstill.

Treatment

Treat the underlying cause.

Atrial Standstill Learning Resources
Flashcards Test your knowledge using flashcard type questions	Feline Medicine Q&A 01

References

Martin, M (2002) ECG interpretation in small animals : 2. Abnormalities in the conduction system In Practice 2002 24: 194-20

Sparks, AH & Caney, SMA (2005) Self-Assessment Colour Review Feline Medicine Manson