Abnormal cardiac rhythms can produce significant alterations in cardiac function, that can contribute to the development of acute heart failure, shock and organ dysfunction secondary to poor tissue perfusion. Knowing how to recognise, interpret, and manage abnormal cardiac rhythm is essential in reducing patient morbidity and mortality. This lecture will present essential information on how to recognise and interpret abnormal cardiac rhythms in the cat, and how to approach management of these rhythms, and provide supportive care for the underlying cause in the emergency setting.