Editing Tachycardia (section)

====Supraventricular====
{{Main|Supraventricular tachycardia}}

This is a type of tachycardia that originates from above the ventricles, such as the atria.  It is sometimes known as paroxysmal atrial tachycardia (PAT).  Several types of supraventricular tachycardia are known to exist.<ref>{{cite web|title=Types of Arrhythmia |url= http://www.nhlbi.nih.gov/health/health-topics/topics/arr/types| work = National Heart, Lung, and Blood Institute (NHLBI) | publisher = U.S. National Institutes of Health |date=1 July 2011 |url-status=live |archive-url= https://web.archive.org/web/20150607165144/http://www.nhlbi.nih.gov/health/health-topics/topics/arr/types |archive-date=7 June 2015}}</ref>

=====Atrial fibrillation=====
[[Atrial fibrillation]] is one of the most common cardiac arrhythmias. In general, it is an irregular, narrow complex rhythm. However, it may show wide QRS complexes on the ECG if a [[bundle branch block]] is present. At high rates, the QRS complex may also become wide due to the [[Ashman phenomenon]]. It may be difficult to determine the rhythm's regularity when the rate exceeds 150 beats per minute. Depending on the patient's health and other variables such as medications taken for rate control, atrial fibrillation may cause heart rates that span from 50 to 250 beats per minute (or even higher if an [[Wolff-Parkinson-White syndrome|accessory pathway]] is present). However, new-onset atrial fibrillation tends to present with rates between 100 and 150 beats per minute.<ref>{{cite web | vauthors = Oiseth S, Jones L, Maza E |url= https://www.lecturio.com/concepts/atrial-fibrillation/ | title= Atrial Fibrillation | website= The Lecturio Medical Concept Library | date= 11 August 2020 |access-date= 3 July 2021}}</ref>

=====AV nodal reentrant tachycardia=====
[[AV nodal reentrant tachycardia]] (AVNRT) is the most common reentrant tachycardia. It is a regular [[supraventricular tachycardia|narrow complex tachycardia]] that usually responds well to the [[Valsalva maneuver]] or the drug [[adenosine]]. However, unstable patients sometimes require synchronized [[cardioversion]]. Definitive care may include [[catheter ablation]].<ref>{{cite journal | vauthors = Katritsis DG | title = Catheter Ablation of Atrioventricular Nodal Re-entrant Tachycardia: Facts and Fiction | journal = Arrhythmia & Electrophysiology Review | volume = 7 | issue = 4 | pages = 230–231 | date = December 2018 | pmid = 30588309 | pmc = 6304791 | doi = 10.15420/aer.2018.7.4.EO1 }}</ref>

=====AV reentrant tachycardia=====
[[Atrioventricular reentrant tachycardia|AV reentrant tachycardia (AVRT)]] requires an [[accessory pathway]] for its maintenance. AVRT may involve orthodromic conduction (where the impulse travels down the AV node to the ventricles and back up to the atria through the accessory pathway) or antidromic conduction (which the impulse travels down the accessory pathway and back up to the atria through the AV node). Orthodromic conduction usually results in a narrow complex tachycardia, and antidromic conduction usually results in a wide complex tachycardia that often mimics [[ventricular tachycardia]]. Most [[antiarrhythmics]] are [[contraindicated]] in the emergency treatment of AVRT, because they may paradoxically increase conduction across the accessory pathway. {{citation needed|date=April 2019}}

=====Junctional tachycardia=====
Junctional tachycardia is an [[automatic tachycardia]] originating in the AV junction. It tends to be a regular, narrow complex tachycardia and may be a sign of digitalis toxicity.<ref>{{cite journal | vauthors = Rosen KM | title = Junctional tachycardia. Mechanisms, diagnosis, differential diagnosis, and management | journal = Circulation | volume = 47 | issue = 3 | pages = 654–664 | date = March 1973 | pmid = 4571060 | doi = 10.1161/01.CIR.47.3.654 }}</ref>