[The electrophysiological bases of aberrant intraventricular conduction during atrial fibrillation].

Twenty-four hours electrocardiogram from 4 patients with chronic atrial fibrillation and intraventricular aberrant conduction were analyzed. Aim of the study was to evaluate the reliability of the Ashman's and Akthar's rules in electrocardiographic differential diagnosis between aberrancy and ectopy. We computed parameters related to 10 RR interval preceding the aberrant conduction (AB+ Group), normal complex QRS (AB-Group) and ectopic QRS (E Group): coupling interval (CI), preceding CI cycle (PCL1), preceding PCL1 cycle (PCL2), the difference between PCL1 an PCL2 (delta PCL1), the difference between CI an PCL1 (delta CI), the mean value (RR10) and the standard deviation (RR10SD) of the 10 QRS complexes preceding the end of the sequence. Specificity of Akthar's rule was 48.7% (range 45-50%), sensibility was 90.1% (range 75-100%). PCL2, delta PCL1 and RR10DS were significantly different between AB+ and AB- Group but not between AB+, AB- and E Group. In this work Akthar's rule showed a better reliability than Ashman's rule but specificity was low (probably related to concealed conduction in atrio-ventricular node). RR10DS, but not RR10, were significantly higher in AB+ Group than AB- Group suggesting that acceleration of the cycle length can provoke CVA by increasing the difference between the refractory period of His bundle branches. Aberrant ventricular conduction cannot be determined by a mathematical rule. In the differential diagnosis of wide QRS during atrial fibrillation only morphological analysis of QRS and the study of coupling interval and compensatory pause are helpful.