Rhythm Interpretation第 23 / 100 题
A regular strip at 68 beats per minute has one upright P wave before every narrow QRS, and every PR interval measures 0.28 second. What is this rhythm?
a.Normal sinus rhythm
b.Sinus rhythm with a first-degree AV block
c.Second-degree AV block, Mobitz II
d.Third-degree AV block
解析
A PR interval that is constant but longer than 0.20 second defines first-degree AV block, in which every impulse still reaches the ventricles but is delayed. Normal sinus rhythm requires a PR of 0.12 to 0.20 second. Mobitz II drops beats without lengthening the PR, and third-degree block shows no consistent relationship between P waves and QRS complexes at all.
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