if you notice there is a fusion beat just before the WCT so I don’t think we can r/o PMT, agree the Only other possibility is tracking An atrial arrhythmia.
Thanks @Yousef Darrat . I still think the initiation is not consistent with PMT for two reasons:
First, the beat before WQRS is beat #3, (and I assume that is the one you refer to as there is a tiny possibly pacing spike at its onset although that spike is not visible in the bottom lead) is probably "pseudofusion" rather than actual "fusion", as it looks almost identical to the underlying native beat (beat #1) and likely generated by a P wave (red arrow) seen at the end of the T wave of the previous beat (#2 ?PVC). If that is the case, then there is no source for a retrogradely conducted P wave to initiate PMT loop.
Second, if we assume beat#3 is actually a "fusion" beat, then that itself negates the possibility of retrograde conduction as the conductive system has to be fully antegradely activated to generate that "fusion" and hence cannot be activated again in retrograde direction. The only assumption will be the presence of a concealed accessory pathway, which is probably unlikely (no information suggestive of that based on these tracings).
Thanks Fathi for the nice illustration and , very good explanation. what I meant initially is a fusion between a PVC and paced and not intrinsic. I looked at the other strip and noted that there is a spike before what we called intrinsic the question i raise here is this BiV pacing? although AV delay was set very long, is the WCT just RV pacing was device being checked? Also Discussion about antegrade conduction absolutely negates any possibility of retrograde can be debated(although I agree with your commment), i will play the devils advocate here as they say and say it depends on the coupling interval, See this link, I don’t have the full article unfortunately
If I understood it correctly, the interesting article above discusses the effect of antegrade concealment on retrograde conduction. However, as you know that does not apply in fusion, where the AVN, and the rest of the conduction system, has to be fully activated antegradely (not just concealed), so it is not plausible to assume its involvement again in retrograde direction. Again, the possibility of a retrograde only pathway (especially with decremental conduction) can not be excluded, although unlikely here.
I doubt this is a CRT with that long PR and wide QRS like you pointed out. May be Naser can clarify the nature of the device.
if you notice there is a fusion beat just before the WCT so I don’t think we can r/o PMT, agree the Only other possibility is tracking An atrial arrhythmia.
Thanks @Yousef Darrat . I still think the initiation is not consistent with PMT for two reasons:
First, the beat before WQRS is beat #3, (and I assume that is the one you refer to as there is a tiny possibly pacing spike at its onset although that spike is not visible in the bottom lead) is probably "pseudofusion" rather than actual "fusion", as it looks almost identical to the underlying native beat (beat #1) and likely generated by a P wave (red arrow) seen at the end of the T wave of the previous beat (#2 ?PVC). If that is the case, then there is no source for a retrogradely conducted P wave to initiate PMT loop.
Second, if we assume beat#3 is actually a "fusion" beat, then that itself negates the possibility of retrograde conduction as the conductive system has to be fully antegradely activated to generate that "fusion" and hence cannot be activated again in retrograde direction. The only assumption will be the presence of a concealed accessory pathway, which is probably unlikely (no information suggestive of that based on these tracings).
Thanks Fathi for the nice illustration and , very good explanation. what I meant initially is a fusion between a PVC and paced and not intrinsic. I looked at the other strip and noted that there is a spike before what we called intrinsic the question i raise here is this BiV pacing? although AV delay was set very long, is the WCT just RV pacing was device being checked? Also Discussion about antegrade conduction absolutely negates any possibility of retrograde can be debated(although I agree with your commment), i will play the devils advocate here as they say and say it depends on the coupling interval, See this link, I don’t have the full article unfortunately
https://pubmed.ncbi.nlm.nih.gov/3687690/
If I understood it correctly, the interesting article above discusses the effect of antegrade concealment on retrograde conduction. However, as you know that does not apply in fusion, where the AVN, and the rest of the conduction system, has to be fully activated antegradely (not just concealed), so it is not plausible to assume its involvement again in retrograde direction. Again, the possibility of a retrograde only pathway (especially with decremental conduction) can not be excluded, although unlikely here.
I doubt this is a CRT with that long PR and wide QRS like you pointed out. May be Naser can clarify the nature of the device.
This is a 40 year lady, she had CHB, device is medtronic dual chamber Pacemaker.