Sudden Wenckebach periods and their relationship to XXXX .

@entity1 @entity1169 @entity907 @entity713 @entity1163 @entity943 @entity7129 @entity2459
Throughout a 9-month period during which 1,125 Holter tapes were reviewed prospectively we identified 13 nonmedicated @entity1 with an @entity943 , which for the purposes of this presentation was categorized, because of their mode of initiation, as @entity2459 (WP). The episodes emerged abruptly from a normal (< or = 200 ms) PR interval with sudden prolongation of PR and PP intervals (and reversed PR-RP relationship) that took place over 1-8 cycles. The postpaced PR interval was shorter than that of the last conducted beat. The episodes were separated into two groups. Group I included 11 @entity1 with symptoms other than @entity1163 and Group II included 2 @entity1 with @entity1163 . There were 26 episodes of sudden WP in Group I. Twenty-five terminated in a single (and one in double) blocked P waves. Most episodes occurred between 10 PM and 7 AM. Symptoms did not correlate with the episodes. Mean 24-hour rates were < 90. In Group II there were 22 episodes, all occurring between 6 AM and 10 PM. The mean sinus cycle lengths before the phenomenon started to occur in Group I (861 +/- 185 ms) as well as the cycle lengths at the onset of block (1,096 +/- 215 ms) were statistically longer than those in Group II (591 +/- 40 ms and 747 +/- 63 ms, respectively, P < 0.0001). Although the mode of onset in the episodes in Group II was similar to Group I, 16 episodes terminated in 2-6 blocked P waves. Thus, the entire number of episodes could be categorized as an unusual type (because of the PR prolongation) of paroxysmal, or advanced second degree @entity713 . Because these @entity1 had negative electrophysiological studies, positive tilt tests, and @entity1163 after oral @entity1169 therapy, they were considered as having @entity907 . In addition, the faster than normal (> 100) mean 24-hour rates) suggested that they also had so-called @entity7129 . In summary, Group I consisted of @entity1 with a normal, benign, vagal-induced second-degree @entity713 , whereas the Holter findings in Group II appeared to reflect unusual (but natural, i.e., nonprovoked) electrocardiographic manifestations of certain @entity1 with @entity907 .
