Editor-In-Chief: C. Michael Gibson, M.S., M.D. ; Associate Editor(s)-in-Chief: Vendhan Ramanujam M.B.B.S 
Synonyms and keywords: Atrio-Hisian fibers
Brechenmacher fibers are accessory pathway taking the form of atrio-Hisian fibers. These are atrial fibers, normal in structure, which bypass the AV node and penetrate into the upper margin of the left side of the bundle of His in its mid part.
Brechenmacher first reported the anatomic finding of an atrio-Hisian bundle in 1974.
Brechenmacher fibers lack the rate-slowing properties of the AV node and thus can rapidly conduct the cardiac impulses. This conduction can lead to a reentrant supraventricular tachycardia, which usually occurs along with enhanced atrioventricular conduction.
Conditions Involving Brechenmacher Fibers
They may be a possible cause for a short PR interval in Lown-Ganong-Levine syndrome along with enhanced atrioventricular nodal conduction. Bypassing the normal conduction system, these fibers lead to a normal QRS complex following the short PR interval in LGL syndrome.
When medical therapy fails while treating LGL syndrome, which is rare, radiofrequency ablation of AV node and its accessory fibers or bundle of His may be considered.