In today's VETgirl online veterinary continuing education podcast, we review the use of lidocaine for chemical cardioversion of AV tachycardia in dogs. Accessory pathways (APs) refer to interruptions of the normal fibrous band that forms the junction between the atria and ventricles (AV junction). Such pathways generally consist of myocardial cells that can conduct electrical impulses between the atria and ventricles, which under normal circumstances occurs only at the atrioventricular (AV) node. Accessory pathways may conduct electrical impulses in the anterograde, retrograde, or both anterograde and retrograde directions. Anterograde conduction results in ventricular preexcitation (i.e., depolarization of a portion of the ventricular myocardium independent of the typical conduction pathway). Retrograde conduction across an accessory pathway creates the potential for a macroreentrant circuit incorporating the atrial myocardium, AV node-His-Purkinje system, ventricular myocardium and the accessory pathway. This scenario can result in a form of supraventricular tachycardia (SVT) known as orthodromic atrioventricular reciprocating tachycardia (OAVRT).