Restitution of action potential duration during sequential changes in diastolic intervals shows multimodal behavior
1Center for Biomedical Engineering, University of Kentucky, Lexington, KY 40506-0070, USA.
Circulation Research
|January 31, 2004
Summary
Action potential duration (APD) restitution is critical for cardiac stability. New protocols reveal that sequential diastolic interval changes, unlike current methods, show multiple APDs for a single DI, impacting predictions.
Area of Science:
- Cardiovascular Physiology
- Electrophysiology
Background:
- Action potential duration (APD) restitution is crucial for understanding cardiac activation instability.
- Current methods for assessing APD restitution do not accurately reflect sequential changes in diastolic interval (DI).
Purpose of the Study:
- To explore APD restitution using a novel pacing protocol that allows sequential and independent manipulation of DI.
- To evaluate the impact of previous activation history on APD restitution.
Main Methods:
- Recorded transmembrane potentials from canine right ventricular endocardial tissue.
- Employed three DI patterns: oscillatory, random, and linear, to simulate different activation histories and compare with existing protocols.
- Developed a new protocol for sequential and explicit control of DI.
Main Results:
- Oscillatory DIs demonstrated a bimodal restitution trajectory, similar to hysteresis.
- APD changes during decreasing DIs were faster than during increasing DIs.
- With minimized prior activation history, multiple APD values were observed for a single DI.
- Restitution relationships derived from sequential DI changes were shallower than those from current protocols.
Conclusions:
- The new pacing protocol enables direct evaluation of memory effects on APD.
- Predicting APD using a unimodal relationship may be inappropriate when DIs change sequentially.
- Findings highlight the importance of considering activation history in APD restitution analysis.
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