 Hi, welcome to nursing school explain in this video about EKG interpretation, specifically atrioventricular or heart blocks, and this video will go into second degree heart blocks type 1 and type 2. If you haven't already done so, I highly recommend watching my basic videos on electrophysiology as well as the EKG interpretation basics where I explain how to read the EKG paper and determine the heart rate as well as go over the normal intervals and rules to memorize so that you have a methodical way of always approaching rhythm strips the same way. Second-degree AV blocks have a type 1 and I type 2 and they have multiple names that people refer to. So second-degree heart block type 1 is also known as a mobits type 1 or a winky buck heart block. I'm not sure where that name came from but it's very specific to this second degree type 1 heart block and the impulses in a second degree type 1 heart block take longer and longer to reach from the atria to the ventricles and we'll look at that when we specifically look at a rhythm strips here in a moment. Second-degree heart block type 2 is also known as a mobits type 2 or a classical heart block which means that only some of the atrial conduction reaches the ventricles and it may progress to a third degree which is a complete heart block if it's not treated. So the second degree type 2 is more dangerous than the type 1 although both may progress to a higher degree third-degree heart block. Here is a review of the conduction system of the heart. Remember the P-wave represents atrial depolarization and the R-wave or the R-wave is the beginning of that QRS complex that represents the ventricular depolarization. So now we just discussed that in the second degree type 1 these impulses take longer and longer to get through so now we might have a normal impulse going through then this one is a little bit delayed and the third one is like extra super slow to come through wherein a third in a second degree type 2 these impulses one might go through all the way and one might not. The next one might go through from the atrial to the ventricles and the second one is just halted and that basically means that we will have a P-wave with no ventricular response. So this one is missing this ventricular response here. Looking at this rhythm strip for a second degree type 1 heart block and by the criteria that we usually methodically analyze rhythm strips with. So rate is can be 60 to 100 but it may be less than 60 because there is that conduction delay in the AV node. For rhythm or regularity there is this factor or this term called regularly irregular. In atrial fibrillation that determinant factor is called irregularly irregular where because of the fibratory waves there is no rhyme or reason to the ventricular response to the atria. We're here when we have this conduction delay there is a certain regularity to this pattern as we'll discuss in the moment here. P-waves are usually upright but there may be greater than one for every QRS which certainly is abnormal and then this here really is key in a type 1 second degree AV block which is that the PRI gets progressively longer until a QRS drops. So looking at this here we can see let's first look at the rate 1, 2, 3, 4, 5. So in our case the rate here is 50 so this applies knowing that the rate is a lot of times less than 60 and then we can see that this is irregular because we have a gap in here so definitely it's irregular actually and so then at this the P-waves they are all upright but we have this one here that's kind of like missing a QRS so there's more than one piece for every QRS because we could count this and this one a P-wave for this following QRS and then regarding the intervals so if the PRI gets progressively longer until the QRS drops so if we start looking at this first one here it starts about here so we count the boxes 1, 2, 3, 4, 5 maybe so 0.20 then the second PRI we counted from this line 1, 2, 3, 4, 5, 6, maybe 7 so 0.28 and this third one here is already longer I can see that so starting here 1, 2, 3, 4, 5, 6, 7, 8, 9 maybe even 10 boxes which would make this 0.40 approximately and then we have the P-wave here with nothing here so we are missing this QRS so this PRI gets progressively longer until the QRS drops so this PRI is here this one is a little bit longer this third one is even longer and then for the fourth one whoops we're missing the QRS and this is very typical of a second degree type 1 heart block now getting back to this regularly irregular so this here basically follows a pattern and then the second pattern would start over right here where this PRI matches this first one the second one matches the second one and if we would see further this pattern here would be repeated in these next four impulses so that's why it's termed regularly irregular and then the last part that we have to look at with our rhythm analysis is the QRS complex and in a winky buck or second degree type 1 heart block the QRS is usually normal so let's find one to look at this first one here seems to lend itself to that very easily so starting at the thick line 1, 2, maybe 2 and a half boxes so 0.10 which makes the QRS normal and again we have this regularly irregular pattern PRI prolonged PRI even longer PRI and then a P with a missing QRS which is this very typical pattern causes for second degree AV block type 1 maybe AV node ischemia due to an occlusion of the right coronary artery basically anything that causes the AV node not to function properly may cause a delay there and a lot of times the culprit is an occlusion or basically a blockage increased parasympathetic nervous system tone anything that slows down the heart rate can cause a second degree type 1 heart block as well medications such as the joxin beta blockers calcium genoblockers specifically varapamil are known to cause second degree type 1 heart blocks and signs and symptoms if the ventricular rate is near normal so if it's around 60 or maybe even a little bit faster the patient might not have any symptoms but if it is due to this AV node ischemia because of an occlusion and that might just be partial of that right coronary artery patient might have signs and symptoms of MI which are hypotension, dysneous shortness of breath, signs and symptoms of CHF, chest pain, altered level of consciousness, anything that we would expect that would be due to a decrease in perfusion because of this blockage. Treatment for second degree AV block type 1 might be to just discontinue the causative medications if the patient has taken too much or maybe there's an overdose once these medications wear off the patient's heart rate will hopefully go back to normal but atropine may be indicated in a second degree type 1 in the meantime until the medications can wear off or if it's really significant and the patient's symptoms are associated with an MI they might need temporary pacing also whenever there's a second degree heart block type 1 it may progress to a second degree type 2 or a third degree heart block which means that we have to carefully monitor the patient for these signs and symptoms and keep an eye on their cardiac monitor because they can get more significant and more severe. So now second degree AV block type 2 also known as a Mobitz type 2 or classical heart block still an incomplete heart block. The rate is usually less than 60 so usually very bradycardic, rhythm is regular, P wave is upright but there is more than one for every QRS complex. Intervals are usually the PRI might be constant but it may be greater than the 0.20 that we would expect as normal. In this specific one our rate let's see is 1, 2, 3, 4, 5, we have 6 QRSs here so our rate would be exactly 60 on this six second rhythm strip. It is not really regular the P waves here are regular but the QRSs you can already see with the naked eye are not regular so I'm going to add here might be irregular and then with the naked eye already you can see that our PRI criteria doesn't match because usually we like to have one P wave for every QRS while in this case we have definitely more than one so we have one P wave here one here and then this is my next QRS so the PRI is usually constant but may be greater than 2.0 so in this case we can't even count this as a PRI because we're missing the QRS right here but when we do have a PRI which would be in these three examples here it's probably constant so let's measure this starting here 1, 2, 3, 4, 5 so that's a 0.20 and then here we have 1, 2, 3, 4, 5 that's normal and then here we have 1, 2, 3, 4, 5 so that's actually normal PRIs here but they might start to get a little bit abnormal you can see it's just borderline from being the the the normal value of the 0.20 and then the QRS if we look at that because when the ventricle does respond so when the impulse does go through the response is normal so the QRS should be less than 0.12 let's find one here that's easy to look at which the first one right here so the QRS starts right here 1, 2, maybe 2.5 so it would be 1.0.10 which makes it a normal QRS so in a second degree hard block type 2 or classic hard block we have greater than one P wave for every QRS and then when we do have the P wave that is followed by the QRS the PRI is constant but all of a sudden we're dropping here so here and here the the conduction does not go through the AV node there's some sort of a block there that does not allow every single P wave to cause that QRS complex to follow examples or causes of second degree type 2 would be schema of the bundle branches due to an occlusion of the left coronary artery remember in type 1 it was usually the right it can be a cute myocarditis or a cute anterior wall MI signs and symptoms may be asymptomatic if the ventricular rate is near normal so in our example here the rate was 60 so the patient might not have symptoms but if it is due to an MI they might have very typical symptoms of heart attack which could be hypotension shortness of breath any signs and symptoms of CHF chest pain or altered LOC again because of this decreased perfusion interventions for second degree type 2 so this is very important here it may rapidly put progress to a complete or third degree heart block therefore usually atropine does not work that's usually indicated in other heart blocks so the patient might need transcutaneous pacing until a permanent pacemaker can be placed here is some credits and references about practice strips I highly encourage you to go to these websites and practice applying these rules to different um rhythm strips so that you can get familiar in identifying these rhythms because particularly these AV blocks can be pretty difficult to identify but the more you practice of course the better you'll get at it here are some other videos in my EKG interpretation playlist specifically these AV blocks here I highly encourage you to also watch the other video on first and third degree heart blocks as well as any other videos that speak your interest please subscribe here on youtube like this video give me a thumbs up follow me on instagram to stay up to date on newest releases as well as my weekly instagram quizzes on monday thanks again for watching see you soon