A variety of reentrant circuits may include reentry around the mitral valve annulus or scar tissue within the left or right atrium. A variety of terms have been applied to these arrhythmias according to the re-entry circuit location, including particular forms, such as LA flutter and LA macroreentrant tachycardia or incisional atrial re-entrant tachycardia due to re-entry around surgical scars. Junctional tachycardia A nonreentrant SVT that arises from the AV junction (including the His bundle). Atrioventricular nodal reentrant tachycardia (AVNRT) A reentrant tachycardia involving 2 functionally distinct pathways, generally referred to as fast and slow pathways. Most commonly, the fast pathway is located near the apex of Koch s triangle, and the slow pathway inferoposterior to the compact AV node tissue. Variant pathways have been described, allowing for slow-slow AVNRT. Typical AVNRT AVNRT in which a slow pathway serves as the anterograde limb of the circuit and the fast pathway serves as the retrograde limb (also called slow-fast AVNRT ). Atypical AVNRT AVNRT in which the fast pathway serves as the anterograde limb of the circuit and a slow pathway serves as the retrograde limb (also called fast-slow AV node reentry ) or a slow pathway serves as the anterograde limb and a second slow pathway serves as the retrograde limb (also called slow-slow AVNRT ). Accessory pathway For the purpose of this guideline, an accessory pathway is defined as an extranodal AV pathway that connects the myocardium of the atrium to the ventricle across the AV groove. Accessory pathways can be classified by their location, type of conduction (decremental or nondecremental), and whether they are capable of conducting anterogradely, retrogradely, or in both directions. 