Telemetry Certification Practice Test

In type 1 second degree heart block, how is the PR interval characterized?

It shortens progressively It remains consistent It progressively lengthens until a QRS is dropped It varies randomly

Correct Answer:

It progressively lengthens until a QRS is dropped

Explanation:

In type 1 second degree heart block, also known as Mobitz type I or Wenckebach, the PR interval is characterized by a progressive lengthening with each successive heartbeat until a QRS complex is dropped. This phenomenon occurs due to a gradual increase in the duration of the PR interval, leading to a point where the electrical impulse fails to be conducted through the AV node, resulting in a missed (or dropped) QRS complex. This pattern can often be observed on an electrocardiogram (ECG) as a repetitive cycle of lengthening PR intervals followed by a QRS drop. The dropping of the QRS complex occurs after the longest PR interval, illustrating the characteristic trait of this type of heart block.

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