Atrial flutter and tachysystoles may complicate the course of all heart diseases or may be discovered independently of any detectable cardiopathy. Functional tolerance mainly depends on the presence and severity of the associated heart disease, if any. A regular cardiac rhythm of 150 beats/minutes at rest suggests a 2:1 block flutter. Electrocardiographic identification of the disorder is usually easy and may lead, in certain cases, to vagal manoeuvres to recognize the atriogramme and the atrium-ventricle relationship. In all cases, 2:1 flutters must be reduced with amiodarone, by electrical stimulation or by electric shock. A prophylactic treatment of recurrences is often, but not always, indicated. The treatment of tachysystoles must take into account the cause of the ventricular rate.