Ventricular fibrillation fibrillation ventricular fibrillation Do not confuse with ventricular flutter, a macroreentrant prefibrillatory rhythm that presents as regular, smooth, large-amplitude sinusoidal waves (sine wave pattern), with the ECG often looking identical when viewed upside down. Ventricular fibrillation is characterized by a chaotic, irregular waveform with deflections of varying morphology and amplitude and represents a state of complete electrical disorganization, where the ventricles quiver instead of contracting synchronously, resulting in total loss of cardiac output. asynchronous contraction or quivering of individual cardiac muscle fibers in the ventricles MPheno.ontology MP:0006110 ventricular arrhythmia ventricular fibrillation phenotype