tag:blogger.com,1999:blog-3364570834099131201.post4994252785688815128..comments2024-03-23T08:57:50.965-04:00Comments on ECG Interpretation: ECG Blog #189 (ECG MP-6) — Is this Some Type of Wenckebach? (SVT - PACs - Flutter - ATach - Laddergram)ECG Interpretationhttp://www.blogger.com/profile/02309020028961384995noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-3364570834099131201.post-38719386051901938082021-01-31T16:29:31.573-05:002021-01-31T16:29:31.573-05:00@ Ahmed — Excellent thought! Phase 4 block (someti...@ Ahmed — Excellent thought! Phase 4 block (sometimes called “pause-dependent” block) is a mechanism of paroxysmal AV block in patients with diseased His-Purkinje systems. It is typically initiated in such patients by premature beats (ie, PACs or PVCs) — however, in this nice review by Uhm et al ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6003538/ ) — they indicate that “various [other] beats or rhythms can cause phase 4 block”. So, as is OFTEN the case — complex arrhythmias (especially when there is associated AV block) often have more than a single potentially correct explanation — and perhaps the initial laddergram I drew (which I show in Part-2 of my above ECG video) could be correct after all — IF this particular patient had severe underlying conduction system disease and was manifesting Phase 4 block …<br /><br />I still favor my laddergram that I show in Figure-2, because it seems to work so well … but without additional monitoring strips and more history — I can NOT rule out the possibility of Phase 4 (pause-dependent) block as you suggest.<br /><br />THANKS again for your comment! — :)ECG Interpretationhttps://www.blogger.com/profile/02309020028961384995noreply@blogger.comtag:blogger.com,1999:blog-3364570834099131201.post-87380833086683746842021-01-31T16:16:38.630-05:002021-01-31T16:16:38.630-05:00@ JJ — Thanks for your EXCELLENT question. I decid...@ JJ — Thanks for your EXCELLENT question. I decided not to go into detail about this — because of the problems with poor resolution (virtually impossible to be certain of the ECG grid, therefore the rate) — and because of lack of other leads with P waves of sufficient amplitude to be able to distinguish P wave morphology from sinus vs ectopic atrial …<br /><br />As stated — your question is EXCELLENT — and it raises the point that sometimes it is very difficult (if not impossible) from a single tracing to tell if we are dealing with “sinus tach” vs ectopic ATach. So, IF you see clear difference in P wave morphology between what you KNOW is a sinus P wave — and especially IF you see other clear features of ectopic ATach (ie, gradual, progressive increase in speed = “warm-up” from an ectopic atrial pacemaker — followed by “cool-down” as the rate gradually slows) — then you KNOW. But in a case like the one we have — I did NOT know for certain. <br /><br />So, I decided to suggest that the underlying atrial rhythm is ectopic atrial tach. ATach does not have to be overly “fast” (ie, could be close to 100-110/minute in a symptomatic patient) — and ATach more than sinus tach in the absence of acute inferior MI would be more likely to produce Wenckebach conduction … but I fully acknowledge that I do NOT know for certain that this is ATach and not sinus tachycardia (which is why I indicated in my “Bottom Line” that additional clinical details would be needed to know better how to approach this patient.ECG Interpretationhttps://www.blogger.com/profile/02309020028961384995noreply@blogger.comtag:blogger.com,1999:blog-3364570834099131201.post-26822796405552423152021-01-31T08:08:22.379-05:002021-01-31T08:08:22.379-05:00great teaching. Wonder why it is atrial instead of...great teaching. Wonder why it is atrial instead of sinus tachycardia?JJhttps://www.blogger.com/profile/17519255052010474217noreply@blogger.comtag:blogger.com,1999:blog-3364570834099131201.post-89446195451663587162021-01-31T03:25:10.985-05:002021-01-31T03:25:10.985-05:00Very interesring tracing. Grateful for your time a...Very interesring tracing. Grateful for your time and effort explaining it. My question is why isn't it possible that the second blocked P wave is due to pause dependent block (caused by the first blocked P) in the INFRANODAL tissue? If this is the case, wouldn't this patient need a pacemaker?<br />Thanks again for sharingAhmed Taherhttps://www.blogger.com/profile/05012749970377565597noreply@blogger.com