What type of tachycardia is AV nodal reentry tachycardia (AVNRT)?

What type of tachycardia is AV nodal reentry tachycardia (AVNRT)?

• A. A demand type tachycardia
• B. A continuous reentry circuit tachycardia
• C. An atrial tachycardia
• D. A ventricular tachycardia

Answer: (B)

AV nodal reentry tachycardia (AVNRT) is characterized as a continuous reentry circuit tachycardia. This type of tachycardia arises from a circuit that typically involves the structures of the heart's atrioventricular (AV) node.

During AVNRT, an electrical impulse continuously loops between two pathways in the AV node, leading to rapid heart rates. This reentrant circuit can occur because of the presence of dual conduction pathways within the AV node, where one pathway may have a longer refractory period than the other. The continuous nature of the reentry circuit allows it to sustain high heart rates, typically ranging from 150 to 250 beats per minute, without significant interruptions.

This understanding highlights why AVNRT is classified specifically as a continuous reentry circuit tachycardia rather than as a demand type tachycardia, which would relate to an increased heart rate due to an increased physiological demand. It is also important to note that AVNRT does not originate from the atria or the ventricles, so classifying it otherwise, such as as an atrial or ventricular tachycardia, is not accurate.