EP Characteristics in Familial WPW. Introduction: A familial form of Wolff‐Parkinson‐White syndrome (WPW) occurs in association with hypertrophic cardiomyopathy and intraventricular conduction ahnormalities. This syndrome, demonstrating autosomal dominant inheritance and segregating with a high degree of penetrance but variable expressivity, has been genetically linked to chromosome 7q3. The purpose of this study is to detail the electrophysiologic characteristics of accessory atrioventricular connections (AC) in four members of a kindred with this syndrome.

Methods and Results: We clinically evaluated 32 members of a single kindred and identified 20 individuals with ventricular preexcitation, abnormal intraventricular conduction including complete AV block and/or ventricular hypertrophy, Genetic linkage analysis mapped the disease gene in this kindred to the chromosome 7q3 locus (maximum logarithm of the odds score = 6.88, θ= 0); recombination events in affected individuals reduced the genetic interval from 7 centimorgans (cM) to 5 cM. Electrophysiologic study of four individuals with preexcitation, identified seven AC (1 right sided, 3 septal, and 3 left sided). All four individuals had inducible orthodromic tachycardia; while three had multiple AC. Bidirectional conduction was demonstrated in 6 of 7 AC. Successful ablation was accomplished in 5 of 7 AC.

Conclusion: The electrophysiologic characteristics and location of AC in family members having this complex cardiac phenotype are similar to those seen in individuals with isolated WPW. Identification of WPW in more than one family member should prompt clinical evaluation of relatives for additional findings of ventricular hypertrophy or conduction abnormalities.(J Cardiovasc Electrophysiol. Vol. 10, pp. 629‐635, May 1999)