Changes

==Aetiology==

==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''' - which can develop secondary to a number of conditions including [[Hypoadrenocorticism|Addison’s disease]], [[Acute Renal Failure|oliguric renal failure]] and [[Urogenital Disease and Anaesthesia|urethral obstruction]]), '''[[Cardiomyopathy|cardiomyopathies]], [[Muscular Dystrophy|muscular dystrophy]] (causing persistent atrial standstill - most commonly seen in the Springer Spaniel), and drug toxicity'''.  

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''' - which can develop secondary to a number of conditions including [[Hypoadrenocorticism|Addison’s disease]], [[Acute Renal Failure|oliguric renal failure]] and [[Urolithiasis|urethral obstruction]]), '''[[Cardiomyopathy|cardiomyopathies]], [[Muscular Dystrophy|muscular dystrophy]] (causing persistent atrial standstill - most commonly seen in the Springer Spaniel), and drug toxicity'''.  

==Clinical Signs==

==Clinical Signs==

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

An ECG should show an '''absence of P waves'''. '''Heart rate is regular''' but normally '''slow''', due to the presence of an '''[[Escape Rhythms|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.  

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

==Treatment==

==Treatment==

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

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

[[Category:Impulse_Conduction_Abnormalities]][[Category:To_Do_-_Cardiovascular]]

 

[[Category: To Do - Siobhan Brade]]

[[Category:To Do - Manson review]]

[[Category:Impulse_Conduction_Abnormalities]]

[[Category:Cardiac Diseases - Dog]][[Category:Cardiac Diseases - Cat]]

[[Category:Expert Review]]