[Tachycardia and ensuing electrosystole].

The benign or severe nature of a ventricular extrasystole depends on a number of parameters which involve the pathophysiological mechanism of the extrasystole: re-entry, exaggerated normal or abnormal automatism and therefore the presence or absence of an underlying cardiac disease. The prognosis depends directly on the morphology, the number and the characteristics of the arrhythmia. Various investigations are often necessary to evaluate this prognosis, including 24 hour Holter monitoring, stress test and electrophysiological investigations.