Measuring ventricular extrasystoles.

Uniform ventricular extrasystoles can be divided into three types: fixed coupling, parasystole, and variable non-parasystolic coupling. Frequency distributions of coupling intervals of ventricular extrasystoles were determined from long electrocardiographic recordings of 51 patients with variable coupling. These distributions were of five types: (a) two distinct coupling intervals, (b) a preponderance of extrasystoles with short coupling intervals and less frequent extrasystoles with progressively longer coupling, (c) a preponderance of long coupling intervals and less frequent extrasystoles with progressively shorter coupling, (d) an even distribution and (3) a central distribution. Interectopic intervals were measured in these electrocardiograms (ECGs). Parasystole was found only in three recordings. It is recommended that the diagnosis of parasystole be made only if the degree of variation of the ectopic cycle (both when it is manifest and when it is concealed) is less than the variation of the coupling intervals. When the ECGs with variable non-parasystolic coupling were compared with 44 ECGs with fixed coupling, it was found that variable coupling was associated with abnormalities of the basic electrocardiographic contour, multiformity of extrasystoles and repetitive extrasystoles.