ATRIAL PACING-INDUCED REVERSE ALTERNATING WENCKEBACH PERIODS - A COMMON ELECTROPHYSIOLOGIC PHENOMENON IN PATIENTS WITH DUAL ATRIOVENTRICULAR NODAL PATHWAYS

Reverse alternating Wenckebach periods (RAWP) have rarely been describ ed, and the significance of dual AV nodal pathways in atrial pacing-in duced RAWP is unknown. Forty-five of 50 consecutive patients (M/F=23/2 7, mean age 40+/-5 years with common type AV nodal reentrant tachycard ia had discontinuous antegrade conduction curves. Atrial pacing reveal ed that pattern A RAWP (23 patients) had the fourth paced beat conduct ed over the fast pathway, and pattern B(18 patients) over the slow pat hway. Four patients had both pattern A and B RAWP during different pac ing cycle lengths. All episodes of atrial pacing-induced RAWP emerged from (or started as) 3:2 AH block, which thereafter were followed by r uns of 2:1 AH block. Comparisons between patterns A and B showed (1) m aximal atrial pacing cycle length with RAWP was longer in pattern A; ( 2) A2H2-A1H1 and A4H4-A1H1 were significantly greater in pattern B; 3) A2H2-A4H4 and H2A4/A2H2 were significantly greater in pattern A. It i s concluded that atrial pacing-induced RAWP is a common electrophysiol ogic phenomenon in patients with dual AV nodal pathways. Furthermore, intermittent slow pathway conduction associated with different AnHn an d HnAn+2 parameters helped the interpretation of different conduction patterns.