Specific mechanisms of supraventricular tachycardia include sinoatrial, intra-atrial, atrioventricular (AV) nodal as well as concealed and manifest bypass tract reentry. In dual pathway reentry, at least one of the pathways involves the AV node, usually the slow pathway and the other pathway, perinodal fibers within the atria. Localization of the perinodal fibers is critical for ablative procedures to eliminate AV nodal tachycardias. Other mechanisms of supraventricular tachycardia include chaotic atrial tachycardia and automatic atrial tachycardia with and without AV block. However, drug therapy includes intravenous adenosine 6 mg, as well as the older standbys of digoxin, calcium and beta-blocking agents, and type 1a and 1c antiarrhythmias. In resistance cases, amiodarone is usually effective. However, for incessant supraventricular mechanisms, catheter or surgical ablative techniques are recommended to eliminate long-term drug administration.