03.13 2nd Degree AV Heart Block Type 2 (Mobitz II)

Hey guys so in this lesson we are going to talk about 2nd degree AV heart block type 2, also called Mobitz II. This rhythm is a little more dangerous than 2nd degree type 1 cause it can cause 3rd degree heart block, so it is important to identify this rhythm quickly so we can do something about it to prevent complications. So let’s go ahead and talk about it.

So in second degree AV heart block type 2, the impulses have difficulties reaching the ventricles just like in type 1 and we end up with a dropped QRS. So the AV node prevents the electrical impulse from getting to the ventricles so the ventricles do not contract and there is no QRS, the AV node can cause this or it can also be from the bundle of his or purkinje fibers. Some impulses do get down to the ventricles but other times they do not and we have a missing QRS. This rhythm is so dangerous and it sets people up for going into 3rd degree heart block or complete heart block so we have to identify it quickly. So let’s break down the characteristics of it and do the 6-step method.

So in step one we need to look to see if the rhythm is regular or irregular, we count the boxes and have about 20 from here to here and another 20 from here to here and about 39 so our rhythm is regular and irregular when we drop a QRS. In step 2 we count the heart rate and we multiply 6 by 10 and get 60 beats per minute, the 1500 method would be inaccurate since it is irregular so we count the apical pulse for a full minute. In step 3 we look at the P:QRS ratio, do we have one P wave followed by 1 QRS and we do except when we drop the QRS. So the P:QRS ratio varies. In step 4 we need to look at the PR interval, in 2nd degree AV heart block type 2, the PR interval is normal and then we drop a QRS, so if we measure this one we have about 5 boxes so we have 0.20 seconds same as here to here then we drop a QRS. So this is the biggest characteristic, the PR interval in normal and then a QRS is dropped. Now in step 5 we look at the QRS complex and we have about 1 and a half boxes so it is 0.06 seconds. So step 6 would be to identify the rhythm and we have 2nd degree AV heart block type 2. So let’s recap the characteristics, the rhythm is regular and irregular when we drop a QRS, the heart rate is usually slow because of the AV heart block but can be normal. The P:QRS ratio varies, it is 1 to 1 until the QRS is dropped. The PR interval is what you need to remember, it is normal until there is no QRS complex and the QRS complex is normal. An easy way to remember this rhythm is by asking Drop a Q? That is type 2! So let’s talk about signs and symptoms and management.

Since 2nd degree AV heart block type 2 is a little more dangerous people will have signs and symptoms and be symptomatic. If we are dropping a QRS every 3 to 4 heart beats, every 3 to 4 hearts beats the ventricles are not contracting, so cardiac output is decreased with signs and symptoms of lightheadedness, dizziness and syncope. If severe enough they will be hypotensive.
The main nursing interventions are to assess the patient immediately and see if they are stable or unstable obtain VS and notify the MD. You also need to prepare to get the patient ready for a pacemaker.
So let’s talk about management.

Management for 2nd degree AV heart block type 2 is to follow the ACLS guidelines, if they are symptomatic and bradycardic we can give them some atropine. We can prepare them for a transcutaneous pacemaker. This is in case they go into 3rd degree heart block of if 2nd degree heart block is severe enough and they are unstable and symptomatic. A permanent pacemaker will be placed to keep them stable and prevent 3rd degree heart block. They are in such a high risk for going into 3rd degree and this is one step away from there so we need to prevent complications.
So the key points and takeaways from this lesson are to remember the characteristics of 2nd degree AV heart block type 2 also called Mobitz II, the electrical impulses are not reaching the ventricles so there is a dropped QRS. Nursing interventions are to quickly identify the rhythm to prevent the patient from going into 3rd degree. Follow ACLS guidelines and give atropine and prepare the patient for a pacemaker either temporary or permanent.

I want to compare the differences between the 2 blocks to make sure you fully understand them. 2nd degree AV block type and type 1 is also called Mobitz I and Wenckebach, 2nd degree av heart block type 2 is called Mobitz II. These are the biggest characteristics that will help you identify the rhythms on an EKG. In 2nd degree AV heart block type 1 the PR interval is progressively getting longer and a QRS is dropped. In second degree AV heart block type 2 the PR interval is normal but the QRS are being dropped periodically. In 2nd degree AV heart block type 1 is relatively pretty harmless unless they are asymptomatic we can just continue to monitor them. 2nd degree AV heart block type 2 can lead to 3rd degree heart block- a deadly arrhythmia. We need to do something about it to prevent complications and prepare them for a temporary or permanent pacemaker and have medications ready in case they are bradycardic. I hope this slide helps so when you see this on an EKG you can tell the difference, are the PR intervals getting longer and we drop a QRS, do we have wencke, wencke, bach that is a 1. Does it look normal and we are dropping Qs, that is a 2!


So I hope that you guys have enjoyed this lesson and understand the difference between 2nd degree AV heart block type 1 and type 2. Make sure you check out the resources attached to this lesson and the cheat sheets that will help you differentiate between the 2, keep practicing and looking at different rhythms to help you identify the difference between the 2. Now, go out and be your best self today! And, as always, happy nursing!