7.8.2 Atrial standstill
Atrial standstill is an uncommon arrhythmia, which is usually caused by hyperIn atrial standstill, P waves are absent but there is apparent conduction of the sinus impulse to the ventricles. A slow sino-ventricular rhythm is present because the cells of the sinus node and internodal tracts are more resistant to hyperkalaemia than the atrial myocardiocytes. The effects of hyperkalaemia on the electrocardiogram are less predictable than are often reported; however, flattening of the P waves and pronounced or inverted T waves may be seen once the potassium levels approach 8-10 mEqL. This may occur in animals with renal failure or a ruptured bladder. In these instances, treatment is aimed at reversal of the initiating disease process if possible, and administration of large quantities of intravenous normal saline to reverse the electrolyte imbalance. Sodium bicarcan also be given if required to encourage potassium to move into cells (0.25-0.5 mEqL).