Rhythm InterpretationQuestion 25 of 100
A strip shows a constant PR interval of 0.20 second on conducted beats, but every third P wave is suddenly not followed by a QRS complex. What is this rhythm?
a.Second-degree AV block, Mobitz I
b.Sinus arrhythmia
c.Second-degree AV block, Mobitz II
d.Premature atrial contractions that are not conducted
Explanation
Mobitz II is identified by dropped QRS complexes with no warning and PR intervals that remain constant on the beats that do conduct. Mobitz I would show the PR lengthening before the drop. Sinus arrhythmia never drops a QRS, and non-conducted premature atrial contractions arrive early with abnormal P waves rather than on schedule.
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