HRS Board Review 2025 New Courses (Reviewers Copy)-Workshop 1_Tomaselli_2025

Video Transcription

Video Summary

The primary observation is that increased pacing rate results in slowed conduction velocity and shortened action potential duration. In a normal heart, increasing rate enhances calcium handling, leading to action potential duration shortening. While cumulative inactivation of potassium currents hastens repolarization, it's the cumulative inactivation of the sodium current that significantly contributes to slowed conduction at high pacing rates, similar to rate-related bundle branch blocks. Thus, the best explanation for these phenomena is the cumulative inactivation of the sodium current.

Keywords

conduction velocity

action potential duration

calcium handling

sodium current

pacing rate