Ventricular flutter is an arrhythmia, more specifically a tachycardia affecting the ventricles with a rate over 250-350 beats/min. It is characterized on the ECG by a sinusoidal waveform without clear definition of the QRS and T waves. It has been considered as a possible transition stage between ventricular tachycardia and fibrillation, and is a critically unstable arrhythmia that can result in sudden cardiac death.
It can occur in infancy, youth, or as an adult.
^Hayashi M, Murata M, Satoh M et al. (July 1985). "Sudden nocturnal death in young males from ventricular flutter". Jpn Heart J26 (4): 585–91. doi:10.1536/ihj.26.585. PMID4057556.CS1 maint: Explicit use of et al. (link)