An unusual effect of interpolated ventricular premature systoles

Abstract

1. 1. A case of interpolated ventricular premature systoles is presented in which there was unusual prolongation of the postextrasystolic P-R intervals; they attained 0.78 second in one instance, and over 0.60 second in three others. 2. 2. The marked prolongation of the postextrasystolic P-R interval after interpolated ventricular premature systoles had a hitherto undescribed effect on the second postextrasystolic beat, namely, prolongation of its P-R and, on one occasion, dropping out of the second postextrasystolic ventricular complex. 3. 3. Analysis showed that the P-R of the first postextrasystolic beat did not depend exclusively on the interval between the beginning of QRS of the premature systole and the next sinus P wave which occurred; some other factor was involved. Reasons are given for the view that this most likely depended upon variations in the retrograde conduction from the point of origin of the ventricular premature systole. The P-R of the second postextrasystolic beat, on the contrary, depended exclusively on the interval between its P and the beginning of the preceding QRS.