Junctional Escapes in Wenckebach Pauses

Report:

Sinus rhythm

Second degree AV block, Möbitz 1

Junctional escape beats

Non-phasic aberrant conduction

Comment:

The ectopic complexes can be either premature or late (escape) beats. Here the Wenckebach pauses are interrupted by junctional escapes, looking slightly different from basic sinus beats. This is called non-phasic aberration12 since it depends on different excitation front from a junctional focus rather than long-short cycle sequence of phasic aberrant conduction.

These beats are less different than they look, as their terminal QRS is distorted by the second non-conducted P wave in each sequence. Some of the size difference can also be attributed to respiration.

Period of complete AV dissociation with somewhat unreliable junctional escape rhythm is shown below (fig 16a).

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