[Differential diagnosis of linked parasystole and extrasystole]

The differentiation between linked parasystole and extrasystole was based on functional tests with exercise and atropin as stimuli. A total of 116 patients (71 with parasystole and 45 with extrasystole) were investigated. Two mechanisms involved in parasystole with fixed links between ectopic complexes were identified: 1) a mechanism of simple quantitative correlation between two pace-makers, 2) a mechanism of the principal pace-maker being discharged with impulses from the parasystolic one. Extrasystole is based on the trigger mechanism of relationship between ectopic excitation and the impulse from the principal pace-maker. Prolonged ECG recording established limits for the maximum interval of links between monotopic extrasystoles and the interectopic interval for paired extrasystole. Extrasystole was shown to be incapable of generating a pace of its own, i.e. a succession of three or more ectopic complexes of similar morphology.