The presence of dual nodal physiology automatically means that the patient will have AVNRT. True or False

• A. False
• B. True
• C. Depends on conduction velocity
• D. Only with atrial fibrillation

Answer: (A)

Dual nodal physiology means there are two conduction pathways within the AV node—the fast and the slow. This arrangement provides the substrate for a reentrant circuit, which is the setup needed for AVNRT. However, simply having two pathways does not guarantee that AVNRT will occur. For sustained AVNRT to happen, you also need a trigger and the right timing of conduction and refractoriness so that impulses can travel antegrade through one pathway and then retrograde through the other to complete a loop. If the necessary conditions aren’t met—such as barriers to reentry, mismatched refractoriness, or lack of a trigger—the tachycardia will not develop. So dual nodal physiology increases susceptibility but does not automatically produce AVNRT. It’s not dependent on atrial fibrillation being present.