Abnormal cardiac conduction can occur in many ways. For example, in this diagram:

• The red dots follow the normal conduction pathway.
• The yellow dot represents conduction via an abnormal "accessory" pathway back toward the AV node (James tract). Typically, impulses travelling these abnormal pathways restimulate the atria and/or ventricles and cause arrythmias.
• The abnormal EKG tracing shown here represents a supraventricular tachycardia.