Atrial standstill is an uncommon bradyarrhythmia defined by complete absence of P waves or other atrial activity on ECG and nodal or ventricular escape rhythms. This electrical disturbance can be temporarily induced by conditions such as severe hyperkalemia and digitalis toxicosis. Alternatively, atrial standstill can be persistent or permanent due to an idiopathic degeneration and fibrosis of atrial and nodal tissue. Pacemaker therapy is the definitive treatment of choice, but due to the often-progressive nature of the cardiomyopathy, ventricular dysfunction and congestive heart failure often occur within months to years of diagnosis. Even with artificial pacing, survival in dogs with this disease is decreased compared to dogs with other, more common bradyarrhythmias.