Nursebob’s MICU/CCU Survival Guide
Cardiology In Critical Care
Arrhythmia Recognition
Second Degree AV Block Type I (Wenckebach)
Packed Red Blood Cells
Nursebob©
2/19/2006
1. Rhythmic impulses originating in the SA node.
A. Conducted through the AV
junction at progressively slower (decremental) speed.
B. P waves
a. Positive in L2
and negative in AVR
b. Occur regularly
at a rate 60-100.
c. A blocked P
wave occurs after 2-5 conducted P waves and this so-called Wenckebach cycle or
period is repeated.
C. The P,Q,R,S ratio of 3:2,
4:3, 5:4 may be constant in all cycles or may vary from cycle to cycle.
D. The PR interval
a. Following a
dropped QRS complex is the shortest and may be normal or prolonged.
b. With each
successive beat the PR interval becomes progressively longer until a P wave is
blocked.
c. QRS complexes
may be normal or wide and bizarre if BBB is present.
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