tag:blogger.com,1999:blog-3364570834099131201.post453917547055622369..comments2024-03-23T08:57:50.965-04:00Comments on ECG Interpretation: ECG Blog #345 — Forward - Backward Conduction?ECG Interpretationhttp://www.blogger.com/profile/02309020028961384995noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-3364570834099131201.post-20358200591801151092022-12-03T08:05:08.568-05:002022-12-03T08:05:08.568-05:00Dr. Ken, thank you very much for your answer and t...Dr. Ken, thank you very much for your answer and this blogMarkohttps://www.blogger.com/profile/07067318617871055984noreply@blogger.comtag:blogger.com,1999:blog-3364570834099131201.post-4714061531852111142022-12-02T18:38:15.148-05:002022-12-02T18:38:15.148-05:00Hi. THANK YOU for your question (and sorry for my ...Hi. THANK YOU for your question (and sorry for my delay in answering). Recognition of junctional tachycardia can sometimes be difficult to distinguish from a reentry SVT rhythm (AVNRT or orthodromic AVRT) — since for all of these rhythms, the QRS is narrow and sinus P waves are absent. That said — the following may be helpful.<br /><br />— Junctional tach is NOT a common rhythm. AVRT and AVNRT are much more common in practice.<br /><br />— Accelerated junctional rhythms or junctional tachycardia tend to occur in certain select situations (ie, congenital heart disase; post cardiac surgery; acute inferior MI; “sick patient” who may be in shock or have other multisystem disease; digoxin toxicity). That is not to say that you cannot have other situations — but they are much less common.<br /><br />— The rate of junctional tach tends to be slower (100-130/minute range) than the faster rates that are more common with reentry SVT rhythms.<br /><br />— Seeing what happened before and/or after the tachycardia may reveal the etiology!<br /><br />That said — sometimes it is difficult to distinguish junctional tach from reentry SVT rhythms.ECG Interpretationhttps://www.blogger.com/profile/02309020028961384995noreply@blogger.comtag:blogger.com,1999:blog-3364570834099131201.post-10056185643516402102022-12-02T18:32:41.800-05:002022-12-02T18:32:41.800-05:00Hi. THANK YOU for your question (and sorry for my ...Hi. THANK YOU for your question (and sorry for my delay in answering). If the reentry “circuit” consists of the normal AV nodaly pathway WITH connection to an accessory pathway ( = AP) — then the direction of travel will determine IF you do (or do not) see a delta wave! Many patients with a reentry SVT have an “occult” AP. By this I mean that the AP ONLY allows retrograde conduction! That is — the impulse travels DOWN the normal AV nodal pathway (and continues on to the ventricles) — with the impulse also traveling “upward” (ie, back or retrograde to the atria via the AP). In this case — the rhythm is an “orthodromic AVRT”.<br /><br />There also are a number of patients with AVRT in which conduction can be EITHER forward down the AP ( = antidromic) — OR — forward down the AV node and back up the AP (which is the “orthodromic” AVRT). Sometimes with an AVRT reentry SVT — the QRS may be narrow during the SVT — but then AFTER conversion, you may see sinus rhythm with delta waves (because conduction may change to going down the AP). And then rarely — AVRT may be antidromic, in which case the QRS during the SVT is wide (and looks like VT) because you are first traveling down the AP.<br /><br />The above possibilities are different than simple “AVNRT” — in which the reentry circuit is entirely contained WITHIN the AV Node.<br /><br />Lots of possibilities. Hope this helps — :)ECG Interpretationhttps://www.blogger.com/profile/02309020028961384995noreply@blogger.comtag:blogger.com,1999:blog-3364570834099131201.post-1239503301899113452022-11-19T04:18:13.851-05:002022-11-19T04:18:13.851-05:00Hello dr. Ken! Thank you for this wonderfull blog....Hello dr. Ken! Thank you for this wonderfull blog. It save lifes. I have one question here. How and when can we suspect and what are the criteria for junctional tachicardia, which is also narrow?Thank you for your answer. Markohttps://www.blogger.com/profile/07067318617871055984noreply@blogger.comtag:blogger.com,1999:blog-3364570834099131201.post-55117683335741411672022-11-18T15:30:21.697-05:002022-11-18T15:30:21.697-05:00If there is an orthodromic re-entry tachcardia the...If there is an orthodromic re-entry tachcardia then there is no delta wave even if there is manifest conduction over the accessory pathway. So not only in concealed pathway I think?Anonymousnoreply@blogger.com