ACLS Review Questions
5. A 67 year old is admitted to the telemetry unit with bradycardia. She has a medical history that includes a NSTEMI two years ago. Her cardiac catheterization at that time showed a 25% blockage in her LAD. Because of some worsening symptoms, she recently went to her family doctor and her dosage of metoprolol was increased from 50mg twice daily to 100mg twice daily and she was scheduled her for a stress test. As you assess her, you find that she is alert and oriented, BP 106/60. Her respirations are regular, symmetrical, non-labored. Her skin is warm and dry. Her heart rhythm is as follows:
a. Idioventricular rhythm
b. Complete heart block
c. 2nd degree heart block type II
d. 1st degree heart block
Answer: C. 2nd degree heart block type II
Answer C. A Mobitz II block occurs below the level of the AV junction which is perfused by the LAD. The ECG characteristics of Mobitz II or 2nd degree heart block type II include nonconducted P waves that are not associated with QRS complexes as well as some conducted P waves. On the conducted P waves there is a consistent PR interval. Rate: Atrial rate is typically normal. Because many of the atrial impulses are blocked, the ventricular rate will be in the bradycardia range, usually with a 2 - 1, 3 - 1, or a 4 - 1 conduction rate.
Rhythm: If the conduction rate is consistent, the R - R interval will be constant, and the rhythm will be regular. If the conduction ratio varies, the R - R will be irregular. P Wave: Upright and uniform. There are more P waves than QRS complexes PRI: Will be constant on conducted beats. QRS: less than 0.12 seconds
Answer A is incorrect because P waves are not present with an idioventricular rhythm. Typically the rate is between 20-40 beats/minute and the QRS complex is widened, > .12.
Answer B is incorrect because with a complete heart block the atrial and ventricles are beating asynchronously and there are no P waves associated with the QRS complexes. Rate: The atrial rate is typically normal. The ventricular rate will be slower. If a junctional focus is controlling the ventricles, the rate will be 40 - 60. If the focus is ventricular, the rate will be 20 - 40. Rhythm: Since the atrial and ventricular foci are firing regularly, the P - P and the R - R intervals will be regular. P Wave: Upright and uniform. There are more P waves than QRS complexes PRI: There is no PRI, because the block at the AV node is complete. There is no association between the P waves and the QRS complexes. QRS: If the focus is junctional, less than 0.12 seconds. If the focus is ventricular, the QRS will be > 0.12.
Answer D: With a first degree heart block there is one P wave for each QRS complex but the PR interval is over .20 seconds. Reviewed 3/1/16
Comments
Post a Comment