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Alternating Wenckebach periodicity: A common electrophysiologic response
The American Journal of Cardiology
|November 1, 1975
Summary
Alternating Wenckebach periods, characterized by progressive atrioventricular block, were studied using His bundle recordings. Findings suggest two distinct block levels explain these complex arrhythmias, differentiating patterns based on blocked P waves.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Electrophysiology
Background:
- Alternating Wenckebach periods involve 2:1 atrioventricular block with progressive PR interval prolongation.
- These periods typically conclude with two or three blocked P waves, indicating complex conduction disturbances.
Purpose of the Study:
- To investigate the electrophysiological mechanisms underlying pacing-induced alternating Wenckebach periods.
- To characterize different patterns of alternating Wenckebach periods using His bundle recordings.
Main Methods:
- His bundle recordings were performed in 13 patients experiencing pacing-induced alternating Wenckebach periods.
- Analysis focused on identifying block location and patterns relative to the His bundle (H deflection).
Main Results:
- Three distinct patterns of alternating Wenckebach periods were identified.
- Pattern 1 (1 patient) showed block distal to the His bundle and Wenckebach periods proximal, ending in two blocked P waves.
- Patterns 2 (4 patients) and 3 (8 patients) demonstrated Wenckebach periods proximal to the His bundle, differing in the number of terminal blocked P waves (three and two, respectively).
Conclusions:
- Alternating Wenckebach periods are best explained by two levels of atrioventricular block.
- Pattern 2 (three blocked P waves) suggests 2:1 block proximally and Type I block distally.
- Patterns 1 and 3 (two blocked P waves) suggest Type I block proximally and 2:1 block distally, with Pattern 1 involving both the AV node and His bundle.