Parasystolic property of the ectopic focus.

Among 4476 ECGs recorded from May 1972 to April 1973, 206 ECGs showed various arrhythmias. All ECGs showing any kind of arrhythmia were recorded for 2 to 4 minutes in order to obtain more than 3 premature beats in one tracing. Of 141 ECGs with premature beats from 126 cases, more than 2 interectopic parasystolic intervals could be measured in 122 cases (96.8% of those with premature beats and 2.7% of all the patients examined). More than 3 coupling intervals could be measured in 117 patients with premature beats. In only 13 of these 117 cases (11.1%), the coupling interval varied less than 0.04 second and less than 0.02 second in 2 cases (1.7%). 1) The parasystolic cycle length ranged between less than 0.20 and more than 2.51 seconds with 82.8% of them being in a range between 0.21 and 1.00 second. 2) The fluctuation rate of the parasystolic cycle length ranged between less than 1.0 and more than 15.1. It was between less than 1.0 and 5.0 in 56,6%, between 5.1 and 10.0 in 30.0% and between 10.1 and more than 15.1 in 13.1%. 3) Fusion beats were observed in 44 of 122 cases in which the interectopic parasystolic cycle length could be determined (36.1%). Of these 44 fusions 14 were found in atrial, 14 in A-V junctional and 16 in ventricular parasystole. 4) Theories of re-entry and ectopic enhancement were discussed.