[Parasystole]

Abstract

Parasystole is usually an extrasystolic rhythm which can occur at every level, but particularly in the ventricle. It is admitted that the parasystolic focus is protected from the environing myocardium by an entry block but can manifest itself. Actually, a pure unidirectional block does not exist and the environing myocardium affects the parasystolic rhythm by an electrotonic current which modulates the output. A non-parasystolic complex which occurs prematurely in the parasystolic cycle delays it. Conversely it accelerates the cycle when it occurs late. By this fact, a parasystole pacing is possible and can lead to a fixed coupling. This arrhythmia is frequently unknown and can be experimentally, reproduced by a sucrose gap preparation.