002 Sinus Rhythm, atrial rate 90 Mobitz II - Blaufuss Multimedia

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177 Sinus Rhythm with First Degree AV Block (P-R 810 msec)...
or Junctional Rhythm with Retrograde P waves, rate 53
Nonspecific S-T and T waves, consider Ischemia
a) There is a seemingly constant P-R (and R-P) relationship throughout; P-R= 810
b) T waves are flat in most leads and inverted in I, aVL, and V4-6
Note: Without additional data, this ECG could either be interpreted as first degree A-V block
with a very long P-R interval or a junctional escape rhythm with retrograde P waves. The
exceptionally long P-R interval (over 800 msec) would seemingly render the first possibility
very unlikely, while the latter diagnosis is supported by a rate typical for junctional escape
rhythm and the suggestion that the P waves in III are inverted (and therefore conducted
retrograde from the junctional focus).
177: The 2 possible mechanisms to explain this rhythm are placed on the Ladder, and the
calipers measure the P-R interval (810 msec) if anterograde conduction is the mechanism of
this arrhythmia. The following ECG obtained on the same patient will confirm the mechanism
underlying this arrhythmia. (Hint: Measure the R-R and P-P intervals with the calipers; a
junctional rhythm should be regular, while sinus rhythm will usually show concurrent variation
in P-P and R-R intervals, while maintaining constant P-R intervals).