A nurse in the critical care unit is monitoring the patient's electrocardiogram (EKG). The nurse notes that the PR interval is growing increasingly prolonged before each QRS. Then the nurse notes that a P-wave occurs with no QRS present. The nurse recognizes this rhythm as which one of the following? 


•In Mobitz type I second-degree AV block, the block occurs in the AV node itself. Ischemia (decreased oxygen) to the inferior heart wall is the usual cause. 

•Mobitz type I second-degree block is often transient, meaning that it occurs and resolves intermittently.  The notable feature of this heart block is a PR interval that continues to prolong until no QRS is generated. 

•Mobitz type I second-degree AV block is also called a Wenckebach block. A good way to remember this is the rhyme: "Longer, longer, longer, drop, now you have a Wenckebach."

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