Compared with the slow pathway, the repolarization time of the fast pathway is:

Compared with the slow pathway, the repolarization time of the fast pathway is:

• A. Longer
• B. Shorter
• C. Similar
• D. Variable

Answer: (A)

In AV nodal dual-pathway physiology, repolarization time (refractory period) differs between the two pathways. The fast pathway, even though it conducts impulses quickly, has a longer action potential plateau and takes longer to return to excitability. The slow pathway, conversely, recovers sooner and can conduct after shorter intervals. This difference is crucial for how reentry circuits form: a premature impulse can travel down the slow pathway while the fast pathway remains refractory, allowing the impulse to eventually re-enter via the fast pathway and sustain reentrant tachycardia. Because of its longer recovery time, the fast pathway’s repolarization time is longer than that of the slow pathway.

In AV nodal dual-pathway physiology, repolarization time (refractory period) differs between the two pathways. The fast pathway, even though it conducts impulses quickly, has a longer action potential plateau and takes longer to return to excitability. The slow pathway, conversely, recovers sooner and can conduct after shorter intervals. This difference is crucial for how reentry circuits form: a premature impulse can travel down the slow pathway while the fast pathway remains refractory, allowing the impulse to eventually re-enter via the fast pathway and sustain reentrant tachycardia. Because of its longer recovery time, the fast pathway’s repolarization time is longer than that of the slow pathway.