As a nurse you want to be familiar with all the types of heart blocks. The types include:
Second-Degree Type I (Mobitz type I or Wenckebach)
Second-Degree Type II (Mobitz type II)
Third-Degree (Complete Heart Block)
Before you review this material be sure to check out the lecture on Second-Degree Type II Heart Block and the comprehensive ECG lecture that details how to analyze heart rhythms.
Second-Degree Type II (Mobitz II) Heart Block
Characteristics and Criteria for Second-Degree Type II Heart Block
The key with differentiating this rhythm from Second-Degree Type I is that with Second-Degree Type II the PR Intervals don’t progressively lengthen like with Type I, but stay constant, and then at some point a QRS complex is dropped. Furthermore, the PR interval can normal or prolonged.
What you will see?
- P-waves will be normal
- Atrial rate (60-100 bpm) and rhythm regular but some p waves won’t have a QRS complex after them. The QRS complex is MISSING.
- Ventricular rate will be slower than atrial rate (usually <60 bpm) and the rhythm irregular
- This is because some of the QRS complexes are missing.
- QRS complexes can be >0.12 seconds or <0.12 seconds depending on the blocked signal within the conduction system
- PR interval constant (the same throughout)…may be prolonged or normal
ECG/EKG Study Guide and Workbook for Nursing Students
“ECG/EKG Interpretation Study Guide and Workbook by Nurse Sarah”. This book contain 100 pages of content featuring 26 ECG rhythm break downs, 51 ECG rhythm analysis practice problems, 100 comprehensive ECG practice questions, worksheets, chart summaries, and more.
You can get an eBook version here: “Nurse Sarah ECG Book” or a physical copy here: “ECG/EKG Interpretation Study Guide by Nurse Sarah“.
Causes of Second-Degree Type II Heart Block
Myocardial infarction with anterior wall involvement, advanced coronary artery disease, damage to the structures that make up the electrical conduction system, medications that slow AV conduction like calcium channel blockers, Digoxin, beta blockers etc.
Treatment for Second-Degree Type II Heart Block
This rhythm is worse than Second Degree Type I (Mobitz I/Wenckebach) and may progress to a third degree heart block.
With this rhythm the ventricular rate is on the slower side, which can affect cardiac output. Therefore, the patient is more likely to have symptoms with this rhythm. If no symptoms present, monitor closely and cardiology may need to be consulted for further evaluation. In addition, the assessment of the patient’s medications will be needed to ensure that they are not taking meds that slow down the AV conduction.
Symptomatic Treatment may include: temporary pacing and insertion of a permanent pacemaker
Now test your knowledge on this material by taking the Second-Degree Type II Heart Block Quiz.
References
American Heart Association | Algorithms. (n.d.). Retrieved September 2, 2022, from https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/algorithms#adult
Mangi MA, Jones WM, Mansour MK, et al. Atrioventricular Block Second-Degree. [Updated 2022 May 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482359/