I'm confused by the part where you say we try to eliminate upper rate behavior by either decreasing the AV delay/PVARP (which makes sense), or increasing the MTR (which doesn't make sense to me). Wouldn't INCREASING the MTR actually increase the likelihood of Pacemaker Wenckebach? Unless by "increasing" you mean make faster or decrease the time. For example, if I increase the MTR to let's say 200bpm from 120 bpm, I'm almost guaranteeing pacemaker wenckebach, aren't I?
Hi Maz Science, excellent question! I probably should have included another example on this as it is one of the more difficult pacemaker topics to learn. Okay, let’s say you have a patient that is programmed with the following settings. LRL = 60 bpm AV delay = 100 ms PVARP = 300 ms MTR = 120 bpm. TARP = 400 ms If we calculate the 2:1 block point we would take the TARP of 400 ms and divide that into 60,000 and we would come up with a 2:1 block point of 150 bpm. This would mean that the patient will be 1:1 conduction up to 120 bpm, they would then go to a Wenkebach from 120 bpm up to 150 bpm. If the Atrial rate were to go up to, or above 150 bpm they would go to a 2:1 block. So by raising the MTR from 120 bpm up to something like 140 bpm we are minimizing some of the Wenckebach behavior. Instead of the patient having Wenckebach from 120 bpm up to 150 bpm they will now only have Wenckebach from 140 bpm up to 150 bpm. If you raise the MTR to 150 bpm the patient would be 1:1 all the way up to 150 bpm and then would go straight to 2:1 block. So in this scenario, if you raise the MTR to 200 bpm you would never actually have any Wenckebach block upper rate behavior. I prefer to have a little Wenckebach window in there. I wouldn't want a patient to be working out and everything is 1:1 and then suddenly they go to a 2:1 block. As you probably already know this will cut their cardiac output in half very suddenly and there is a potential that the patient could get dizzy or even pass out. I don't know if it is true or not but I was taught that by having a little Wenckebach window in there it might serve as a warning to the patient. They might be able to feel the dropped beats and then realize that they need to slow down. Hope this helps!
This lecture is nothing short ov heaven for newbies ,,,,,,,,,,, i had only heard abt PMT , but now actually understanding it opens a while new world of prograaming ............ Thankyou , obliged
Pacemakers are designed to be in the body for many years so most likely there is no danger of leaving it in. But, it would be a good idea to check with the pacemaker clinic that he use to follow at.
26:40, why intrinsic PP interval with dropped pace QRS is longer, than other PP interval. PP interval is from intrinsic activity of SA node, and SA node here is OK, or pacient has SSS syndrome?
Peter Blahút - Good catch! I must have missed that when I created the PowerPoint. Yes, the SA node is typically functioning properly in this situation and therefore the P to P interval should have been consistent all the way across and not longer after the dropped pace.
thank you for the great infos, really helpfull. my question is with the 2:1 Block why didnt the pacemaker start a VA-Interval and LRL and reacted accordingly( why waited so long tell a P-wave schowed up)
Hi Joha, yes we have a fast heart rate in this situation. The upper rate behavior only occurs when the patient's intrinsic atrial rate is faster than the TARP or PVARP timer which is usually at a faster rate. In reality, the pacemaker is actually starting a VA-Interval and a LRL timer, it's just that those timers wouldn't have timed out which is why the pacemaker waits so long and won't atrial pace. Lets say that a patient is programmed with a Lower Rate Limit (LRL) of 60 bpm and has a 2:1 block point of 120 bpm but, there intrinsic atrial rate is 130 bpm. That would mean that the 2:1 block rate that the patient would be at is 65 bpm. Since 65 bpm is faster than 60 bpm the LRL won't time out, and depending on how the pacemaker is programmed the VA timer won't time out either. I hope that made sense.
I’m a senior cardiology fellow nearing my graduation and after watching this i’m now really considering going into EPS. Thank you! I can’t understand it in braunwald no matter how i read it! This is great!
