chronaxie
Pronunciation: KRON-ax-ee
The minimum pulse width required to achieve capture at twice the rheobase voltage.
Full Definition
Chronaxie is a fundamental electrophysiological parameter that describes the relationship between stimulus strength and duration for cardiac tissue excitation. It represents the minimum pulse width needed to achieve consistent cardiac capture when the stimulus amplitude is set at twice the rheobase (the minimum voltage threshold for capture with an infinitely long pulse). Understanding chronaxie is crucial for optimizing pacemaker programming to achieve reliable capture while minimizing battery drain. Modern pacemakers typically use pulse widths between 0.4-1.0 milliseconds, which are generally well above the chronaxie values for healthy cardiac tissue. Changes in chronaxie over time can indicate lead maturation, tissue fibrosis, or other factors affecting the pacing interface.
Usage
Usage note: Often confused with rheobase; ensure proper distinction in technical documentation.
In Context
- "The chronaxie value increased from 0.3 to 0.8 ms over the first month post-implant due to lead maturation." — Clinical research paper
- "Determining the patient's chronaxie helps optimize pulse width settings for maximum battery longevity." — Device programming manual