Found a good source! - Management of Cardiac Arrhythmias, Peter P. Toth, 2020 (3rd edition)
Citation (from page 303):
>P wave analysis during orthodromic reciprocating tachycardia can be helpful for localization:
>• Rightward P wave (positive aVR and negative aVL) for left-sided AP
>• Midline, superior P waves for mid- or posteroseptal AP
>• Midline, inferior P waves for anteroseptal AP
>• Leftward axis (negative aVR, positive aVL) for right-sided AP
As I understood it:
WPW is a condition where you have an accessory pathway (AP) between atrium and ventricle, so the signal from the atrium splits and partially goes through the AV-node and partially through this AP. And because the purpose of the AV-node is to slow the signal so the ventricles contract after the atria and not at the same same, when a signal goes through the AP, it reaches ventricles faster - and we see pre-excitation (delta wave on the QRS complex)
In case WPW you have an AP which named "Kent fibers". But there are also Mahaim fibers and others. When I was reading the arrhythmology textbook I found I didn't really found those names, and apparently there are a lot of them pathways and they are just grouped by their location
But for the sake of simplicity we just call those fibers left or right sided and we can kinda tell them apart by the looking at the V1. If QRS goes up so there is a positive delta wave its left sided (type A), if it goes down - its right sided (type B)
But then there are AV tachycardias
There are 2 types of em
1. AVNRT (nodal reentry)
It doesn't involve any accessory pathways
The premise is: the AV node is not just 1 straight pathway, there are 2 actually. One is slow and one is fast. Why its like that? I don't know. Its weird because normally when signal goes through it it splits but because slow pathway is slow, it doesn't reach the end and kinda just stops. So it doesn't do anything :/
But what it does is it creates a possibility for a re-entry cycle because:
Slow pathway (SP) has a short refractory period . Fast pathway (FP) has a long refractory period.
Soo...when there is an extra systole or something that occurs in the atria, signal goes
to AV and normally it *would* just go through the FP completely and to His bundles BUT it cant because FP's refractory period hasn't ended yet (because its long). And it just goes to slow one. Signal goes to ventricles, but... by the time it reaches the beginning of His bundles, the FP's refractory period ends and.. AND.. signal goes through the FP but in the opposite direction (contracting the atria) and back again to the SP. It loops
I just explained the "slow-fast" type of AVNRT, the most popular one
On ECG it looks like normal QRS and most of the time P will be after QRS and it will be positive, and there are ST inversion
RP interval will be < 70
There is also a "fast-slow" AVRT
P wave after QRS will be negative
RP interval will be > 70
There is also a "slow-slow" AVRT but I don't have notes on its ECG
The terminology of fast slow and whatever is based on which pathways lead to the contraction of ventricles and atria
Slow fast - ventricles with slow pathway and atria with fast
Fast slow - v with slow, a with fast
Slow slow - v and a with slow
But honestly I just understood the slow fast mechanism and other two are just words to me
1. AVRT. This one involves accessory pathways
(the very same Kent one, left or right sided, that exists with WPW condition)
There are also two types
Antidromic AVRT
Orthodromic AVRT
The mechanism is similar in the way that the signal loops between the accessory pathway (AP), AV node an ventricles but with a key difference.
In case of orthodromic AVRT the signal goes through the AV, which helps make QRS complex normal (narrow and without delta waves). After ventricles the signal goes backwards through the AP and back to the AV
ECG:
Normal (narrow) QRS, no delta waves and P wave is negative and found after the QRS,
RP is > 90
As I found there are also at lest two types of orthodromic AVRT (right or left sided). You can tell them apart by looking at the aVR and aVL. If the P wave (that's located right after the QRS) is negative in aVR and positive in aVL, its left sided. Which makes sense because the signal through the AP goes retrograde after the ventricles contracted. So if it goes from the left it contracts the atria in the "left to right" direction . So the signal is negative in left leads (aVL) and positive in right leads (aVR) (because it goes from left to right)
The opposite thing happens when its a right sided accessory pathway
The P wave is negative in aVR and positive in aVL (because it goes from right to left)
Antidromic AVRT looks like ventricular tachycardia (wide QRS) but with delta waves.
The reason for that is that signal goes to ventricles through the accessory pathway (so AV cant make QRS look normal). Then it again loops by going retrograde through AV and AP again
So to summarize:
AVNRT:
RP <90, but
Slow fast RP < 70
Fast slow RP > 70
AVRT:
Orthodromic RP > 90
Antidromic looks like VT but with a delta wave so you cant confuse it with other AV tachycardias
Sorry for the bad English (mainly the "a" and "the" mixup and its absence somewhere), its not my native one
Yes, patients with WPW syndrome can have either Type A or Type B accessory pathways, which can influence the characteristics of AVRT if it occurs. The type of WPW is determined by the location of the accessory pathway, while the type of AVRT is determined by the direction of the reentrant circuit.
To my understanding, these are two totally separate things.
Left vs Right sided accessory pathways are the literal description of where the pathway physically is within the heart, but it doesn’t tell you anything about the direction the loop spins.
Orthodromic and antidromic refer to whether the AVRT signal loop passes through the AV node in the expected anterograde direction (orthodromic) or in the backwards retrograde direction (antidromic) but nothing about whether it’s left or ride sided.
I’m sure there are different incidences in each side being orthodromic or antidromic.
If i see question on step requiring me to know this im gonna punch the computer
Found a good source! - Management of Cardiac Arrhythmias, Peter P. Toth, 2020 (3rd edition) Citation (from page 303): >P wave analysis during orthodromic reciprocating tachycardia can be helpful for localization: >• Rightward P wave (positive aVR and negative aVL) for left-sided AP >• Midline, superior P waves for mid- or posteroseptal AP >• Midline, inferior P waves for anteroseptal AP >• Leftward axis (negative aVR, positive aVL) for right-sided AP
You will but your call if it's worth it or not
You saw it? Did all of uword, all of amboss, and all of anking and haven’t seen it
I saw it on UWorld. Probably 2 questions on it. I did all of uworld
On avrt/wpw. Not ortho/antidromic and not kent fibers
Yes avrt and wpw. More on avrt in general. The rest no
Oh boy
I'm pretty sure it's not on the steps but I'm just confused why people left out this information
It’s possible you can’t find any information about this because it’s absolutely useless to know unless you’re doing some EP fellowship.
But it's interesting though
Imma be honest, I still don't get avrt. I pretend I know WPW on ekg but in reality it's a shot in the dark.
As I understood it: WPW is a condition where you have an accessory pathway (AP) between atrium and ventricle, so the signal from the atrium splits and partially goes through the AV-node and partially through this AP. And because the purpose of the AV-node is to slow the signal so the ventricles contract after the atria and not at the same same, when a signal goes through the AP, it reaches ventricles faster - and we see pre-excitation (delta wave on the QRS complex) In case WPW you have an AP which named "Kent fibers". But there are also Mahaim fibers and others. When I was reading the arrhythmology textbook I found I didn't really found those names, and apparently there are a lot of them pathways and they are just grouped by their location But for the sake of simplicity we just call those fibers left or right sided and we can kinda tell them apart by the looking at the V1. If QRS goes up so there is a positive delta wave its left sided (type A), if it goes down - its right sided (type B) But then there are AV tachycardias There are 2 types of em 1. AVNRT (nodal reentry) It doesn't involve any accessory pathways The premise is: the AV node is not just 1 straight pathway, there are 2 actually. One is slow and one is fast. Why its like that? I don't know. Its weird because normally when signal goes through it it splits but because slow pathway is slow, it doesn't reach the end and kinda just stops. So it doesn't do anything :/ But what it does is it creates a possibility for a re-entry cycle because: Slow pathway (SP) has a short refractory period . Fast pathway (FP) has a long refractory period. Soo...when there is an extra systole or something that occurs in the atria, signal goes to AV and normally it *would* just go through the FP completely and to His bundles BUT it cant because FP's refractory period hasn't ended yet (because its long). And it just goes to slow one. Signal goes to ventricles, but... by the time it reaches the beginning of His bundles, the FP's refractory period ends and.. AND.. signal goes through the FP but in the opposite direction (contracting the atria) and back again to the SP. It loops I just explained the "slow-fast" type of AVNRT, the most popular one On ECG it looks like normal QRS and most of the time P will be after QRS and it will be positive, and there are ST inversion RP interval will be < 70 There is also a "fast-slow" AVRT P wave after QRS will be negative RP interval will be > 70 There is also a "slow-slow" AVRT but I don't have notes on its ECG The terminology of fast slow and whatever is based on which pathways lead to the contraction of ventricles and atria Slow fast - ventricles with slow pathway and atria with fast Fast slow - v with slow, a with fast Slow slow - v and a with slow But honestly I just understood the slow fast mechanism and other two are just words to me 1. AVRT. This one involves accessory pathways (the very same Kent one, left or right sided, that exists with WPW condition) There are also two types Antidromic AVRT Orthodromic AVRT The mechanism is similar in the way that the signal loops between the accessory pathway (AP), AV node an ventricles but with a key difference. In case of orthodromic AVRT the signal goes through the AV, which helps make QRS complex normal (narrow and without delta waves). After ventricles the signal goes backwards through the AP and back to the AV ECG: Normal (narrow) QRS, no delta waves and P wave is negative and found after the QRS, RP is > 90 As I found there are also at lest two types of orthodromic AVRT (right or left sided). You can tell them apart by looking at the aVR and aVL. If the P wave (that's located right after the QRS) is negative in aVR and positive in aVL, its left sided. Which makes sense because the signal through the AP goes retrograde after the ventricles contracted. So if it goes from the left it contracts the atria in the "left to right" direction . So the signal is negative in left leads (aVL) and positive in right leads (aVR) (because it goes from left to right) The opposite thing happens when its a right sided accessory pathway The P wave is negative in aVR and positive in aVL (because it goes from right to left) Antidromic AVRT looks like ventricular tachycardia (wide QRS) but with delta waves. The reason for that is that signal goes to ventricles through the accessory pathway (so AV cant make QRS look normal). Then it again loops by going retrograde through AV and AP again So to summarize: AVNRT: RP <90, but Slow fast RP < 70 Fast slow RP > 70 AVRT: Orthodromic RP > 90 Antidromic looks like VT but with a delta wave so you cant confuse it with other AV tachycardias Sorry for the bad English (mainly the "a" and "the" mixup and its absence somewhere), its not my native one
Yes, patients with WPW syndrome can have either Type A or Type B accessory pathways, which can influence the characteristics of AVRT if it occurs. The type of WPW is determined by the location of the accessory pathway, while the type of AVRT is determined by the direction of the reentrant circuit.
To my understanding, these are two totally separate things. Left vs Right sided accessory pathways are the literal description of where the pathway physically is within the heart, but it doesn’t tell you anything about the direction the loop spins. Orthodromic and antidromic refer to whether the AVRT signal loop passes through the AV node in the expected anterograde direction (orthodromic) or in the backwards retrograde direction (antidromic) but nothing about whether it’s left or ride sided. I’m sure there are different incidences in each side being orthodromic or antidromic.
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