[Mechanisms of the occurrence of parasystole and extrasystole]

Mechanisms involved in the development of parasystole and extrasystole are substantiated on the basis of vast clinical material (261 patients with parasystole and 45 with extrasystole). The use of functional tests employing exercise and atropine contributed to both the correct diagnosis of parasystole and extrasystole and a logical explanation of the mechanisms governing their development. Prolonged ECG recording identified, for the first time ever, the limits of the maximum admissible coupling interval for normotopic extrasystole, as the preliminary diagnosis of the nature of the arrhythmia was only made after the said tests. Parasystole was shown to be rooted in a pathologic automatism, and extrasystole, in the summation of extrasystolic focus potentials and the principal pacemaker potential during movement as well as the principal pacemaker impulse along the route of the minor circular wave on Purkinje' level. The localization of ectopic foci in parasystole and extrasystole confirms the hypothesis of the mechanisms involved in these arrhythmias. A parallel study of parasystole and extrasystole defined parasystole as active heterotopia, and extrasystole, as passive heterotopia incapable of generating a rhythm.