Medical Surgical EKG #1

Question

During an admission assessment, a client informs the nurse of a history of having a certain type of heart block. Previous records were analyzed by the nurse and the client was found to have the following ECG the previous year.


The nurse interprets last year’s ECG as:

Answers

  1. First degree AV block
    • Rationale:

      This answer is not correct because a first degree AV block is usually asymptomatic and is a common conduction disturbance. The PR interval exceeds 0.20 in first degree heart block (normal PR interval is 0.12 – 0.20 seconds). Second degree AV type I (Wenckebach) heart block is an arrhythmia which shows increasing prolongation of the PR interval, just before a QRS complex drops or disappears. Then the gradual prolongation repeats itself again, until there is another drop of the QRS complex.

  2. Sick sinus syndrome
    • Rationale:

      This answer is not correct because sick sinus syndrome can cause various manifestations on the ECG, including sinus bradycardia, sinoatrial block, sinus arrest, and alternating patterns of tachycardia and bradycardia. Second degree AV type I (Wenckebach) heart block is an arrhythmia which shows increasing prolongation of the PR interval, just before a QRS complex drops or disappears. Then the gradual prolongation repeats itself again, until there is another drop of the QRS complex.

  3. Second degree AV type I (Wenckebach)
    • Rationale:

      This answer is correct because a second degree AV type I (Wenckebach) heart block is an arrhythmia which shows increasing prolongation of the PR interval, just before a QRS complex drops or disappears. Then the gradual prolongation repeats itself again, until there is another drop of the QRS complex. This ECG reflects various failures of conduction of the electrical impulse through the AV node, which shows that some P waves lack a QRS complex.

  4. Third degree AV block
    • Rationale:

      This answer is not correct because third degree AV block or complete heart block is where there is no conduction through the AV node, which causes complete dissociation between the atria and ventricles. The ECG will reflect no relation between the P-waves and the QRS complexes. Second degree AV type I (Wenckebach) heart block is an arrhythmia which shows increasing prolongation of the PR interval, just before a QRS complex drops or disappears. Then the gradual prolongation repeats itself again, until there is another drop of the QRS complex.

Overview

Mobitz second degree AV type I (also known as Wenckebach) heart block is an arrhythmia which shows increasing prolongation of the PR interval, just before a QRS complex drops or disappears. Then the gradual prolongation repeats itself again, until there is another drop of the QRS complex. The block could be caused by medications, ischemic episode, infection, and heart surgery.

Explanation

Learning Outcomes

Second degree AV type I (Wenckebach) heart block is an arrhythmia which shows increasing prolongation of the PR interval, just before a QRS complex drops or disappears. Then the gradual prolongation repeats itself again, until there is another drop of the QRS complex. This ECG reflects various failures of conduction of the electrical impulse through the AV node, which shows that some P waves lack a QRS complex. Some clients are asymptomatic and require no treatment and some are symptomatic, requiring treatment with atropine.

Test Taking Tip

Remember that only the second degree heart blocks actually drop a QRS complex. This will help focus the student on the most likely correct answer.

Video Rationale