[Heart failure due to atrial standstill in a cat].

A 7.5-year-old male Persian cat with a history of asymptomatic hypertrophic cardiomyopathy was examined for severe lethargy and dyspnoea. Physical examination revealed bradycardia (60 beats/ minute), and ECG investigation revealed persistent atrial standstill that was most likely caused by atrial fibrosis. Persistent atrial standstill is a very rare cardiac condition in cats and is characterized by a complete lack of mechanical, electrical, and possibly endocrine function of the atria. Several pathophysiological mechanisms can cause atrial standstill and include hyperkalaemia, intoxication, and atrialfibrosis. On the basis of the clinical findings, atrial fibrosis was the most likely cause of atrial standstill in this cat. Treatment depends on the underlying cause, but pacemaker implantation can be considered if there are structural abnormalities. The prognosis is guarded in such cases. In this particular case, the cat was euthanized at the owner's request.