Talk:Junctional tachycardia

AVNRT as a type of JT?

The CV disease template implies that junctional tachycardia includes both junctional ectopic and AVNRT, but this article implies that AVNRT is not a type of JT. Which is correct? Myoglobin (talk) 18:50, 26 March 2018 (UTC)

The difference between an ectopic focus in the AV node and a reentrant circuit in the AV node is usually not known until the time the arrhythmia is permanently cured via catheter ablation. Then it never gets to be observed again. Via non-invasive EKG, an ectopic focus and a reentrant circuit should look extremely similar if they are in the same location, although the most common heart rates are different. Without electrodes inside the heart, all of the EKG signal will come from things outside the source of the arrhythmia. Response to drugs is different but not diagnostic - a hypothetical "pure" negative dromotropic agent would "only" terminate AVNRT but not junctional ectopic tachycardia. The nearly-pure negative dromotropes like diltiazem and verapamil do in fact also decrease automaticity, so they can convert either type of arrhythmia to sinus rhythm. In summary: It is impossible to actually know whether a tachyarrhythmia arising in the AV node is AVNRT or an ectopic focus prior to a catheter ablation, which will almost always be curative, so I don't think cardiac electrophysiologists have reached a consensus on the use of this term. AVNRT has "reentrant" in the name, but "junctional tachycardia" just says the location and the rate, not the mechanism. I would be astonished if use of these terms by cardiac electrophysiologists was not inconsistent in patients who have not yet been catheterized. This is a distinction that can largely only be made after the arrhythmia was permanently cured. Prior to that time, the diagnosis is usually "SVT, most likely (insert hypothesis)". Fluoborate (talk) 11:28, 29 April 2019 (UTC)

Fluoborate is correct. While AVNRT is distinct from a junctional ectopic tachycardia (JET), both arise from the AV node. Somewhat confusingly, the two arrhythmias can be grouped together as "junctional tachycardias", but this term is not often used in UK practice as far as I am aware. Instead, we would generally refer to both JET and AVNRT as regular narrow-complex tachycardias before a definitive diagnosis had been made using invasive electrophysiological studies. Until the wires are in the heart it can often be difficult to tell the difference between AVNRT, AVRT (a narrow complex tachycardia involving an accessory pathway - may be obvious as part of the Wollf-Parkinson-White syndrome but may be concealed), JET, and some types of atrial tachycardia.

The crucial difference between the two is the mechanism of arrhythmia. JET is an automatic arrhythmia (an arrhythmia where a group of cells start beating of their own accord and acting like pacemaking tissue) arising from the AV node which may be seen spontaneously but often arises after catecholamines such as isoprenaline have been given. In contrast, an AV nodal reentrant tachycardia (AVNRT) is, as the name suggests, a re-entrant arrhythmia arising from the AV node that occurs in those with "dual AV-node physiology" where part of the AV node conducts relatively rapidly while part of it conducts relatively slowly. AVNRT results from impulses repeatedly travelling down the slow and up the fast pathways of the AV node in a loop (or rarely in the other direction).

The article is poorly written - I will try to improve it when I have the time. PeaBrainC (talk) 12:44, 29 April 2019 (UTC)

Wow, thank you both for the thorough explanation! The particular sentence I was asking about still doesn't make sense: "Junctional tachycardia can appear similar to atrioventricular nodal reentrant tachycardia"; did they instead mean JET can appear similar? I think both JET and AVNRT are types of JT, which just describes a tachycardic rhythm with a source in the AV/junctional area. Is that thinking at all correct? Myoglobin (talk) 13:01, 29 April 2019 (UTC)

Yes, you're right. It should read that JET can appear similar. PeaBrainC (talk) 13:31, 29 April 2019 (UTC)

My edits on 2019-04-29

I corrected the spelling of "amiodarone". I changed the phrase "cardio-version" (sic) to "electrical cardioversion" in both of the two places where it occurs. The two places where these terms are used are slightly different, but they say the same thing in terms of ideas: "Amiodarone is used to treat this arrhythmia, cardio-version is not used." Both sentences originally said "amiodarone for rate control", so I "corrected" it to "rhythm control" or "to correct the rhythm". A rate control agent is a type of antiarrhythmic, and amiodarone is most definitely "the other kind", amiodarone is a rhythm control agent. (Edit / erratum: Amiodarone is widely considered class III, but it is not "pure" class III, it has weaker actions that would qualify as a rate control agent. So it's both, but the thing I wrote on the actual Wikipedia page didn't say "amiodarone is a rhythm control agent", it said it fixes "the rhythm". I just wanted to remove "rate control" to limit confusion.) Of course, successful rhythm control in a tachyarrhythmia will also bring down the rate. Because the arrhythmia has been corrected. I changed "cardio-version" to "electrical cardioversion" because IV amiodarone is chemical cardioversion. Both sentences say "cardio-version is not used" rather than "should not be used", and I did not change this, but it seems incorrect. The first problem is that it is not cited. The second problem is that even if it were cited and true, the fact that it "should not be used" is very different than "is not used". Inappropriate use of electrical cardioversion in AFib patients who are not on anticoagulants is indeed used - and then it kills the patient via ischemic stroke, when the blood clot you just shook loose from the left atrium reaches the brain. Saying "is not used" sounds like wishful thinking, "should not be used" is actual advice. I'm not going to change that, because I don't even know if it should or should not be used in this case. AFib is a lot more common, so there is a lot of data (and discussion) about when electrical cardioversion should and should not be used. Fluoborate (talk) 11:49, 29 April 2019 (UTC)