A study of the factors influencing the appearance of the Ashman phenomenon

The electrocardiograms of 29 patients with atrial fibrillation and aberrancy (Ashman phenomenon) were studied. The length of the cycles manifesting aberrancy (R-RA) varied from 270 to 520 msec (mean 372 +/- 55). It correlated negatively with the heart rate (r-0.899, p less than 0.001) and for equal heart rates in separate persons it varied with the length of the preceding R-R cycle (p less than 0.01). Above a critical R-RA length of 520 msec and outside an R-R/R-RA ratio range of 1.5-3.6 aberrancy is never observed: this finding is important for the differentiation of aberrancy from ventricular ectopy.