Significance of pre-excitation of the presence of intraventricular and atrioventricular conduction disturbances

Summary An analysis is made of the ventricular complex in personal and published cases of pre-excitation (typical or atypical Wolff-Parkinson-White Syndrome) in which intraventricular or atrio-ventricular conduction disturbances were present before appearance of pre-excitation. On the basis of this analysis the conclusion is made that a prolonged or normal P-R interval or a shortening of the QRS interval after appearance of pre-excitation is in favor of a location of the aberrantly conducting A-V pathways in or near the A-V node. In one of the illustrated cases the pre-excitation pattern was accompanied by earlier beginning of ventricular contraction without change in the time of appearance of the carotid pulse.