Vectorcardiographic observations of postextrasystolic T wave changes associated with interpolated ventricular beats.

A recent study of the postextrasystolic T wave changes, associated with interpolated premahire ventricular beats, revealed that this phenomenon is not rare and, unlike the T wave changes which occasionally occur in the first sinus beat following the more common premature ventricular beats with compensatory pauses, are not usually related to the presence of significant heart disease.’ Despite the establishment of the clinical significance of this phenomenon, the cause has remained obscure. One theory was that of Scherf2 who proposed that the postextrasystolic T wave changes seen after interpolated extrasystoles are secondary to aberrancy in ventricular depolarization. Although several electrocardiograms of the patients described in a previous study demonstrated slight aberrancy in the QRS complex of the postextrasystolic beat, many of them did not, and in those that did, the T wave changes were in excess of what might be expected from secondary T wave changes of QRS aberrancy.1 An opportunity to further evaluate this aspect of the problem arose when a patient was observed to be having occasional interpolated extrasystoles with postextrasystolic T wave changes during a routine clinic visit.