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Dynamic origin of spatially discordant alternans in cardiac tissue
Hideki Hayashi1, Yohannes Shiferaw, Daisuke Sato
1Division of Cardiology, Cedars-Sinai Medical Center, Los Angeles, California, USA.
Biophysical Journal
|October 31, 2006
Summary
Spatially discordant alternans, a heart rhythm disturbance, can arise from dynamic processes, not just tissue differences. Mathematical modeling and optical mapping reveal how these alternans patterns pinpoint underlying mechanisms.
Area of Science:
- Cardiology
- Computational Biology
- Biophysics
Background:
- Alternans, characterized by beat-to-beat variations in cardiac cell electromechanical response, are linked to life-threatening ventricular arrhythmias.
- Spatially discordant alternans, where adjacent regions exhibit out-of-phase action potential durations, present complex patterns in optical mapping studies.
- The precise mechanisms initiating discordant alternans and their spatiotemporal dynamics remain incompletely understood.
Purpose of the Study:
- To investigate the underlying mechanisms of spatially discordant alternans using mathematical modeling.
- To determine if dynamic changes in alternans spatial distribution can identify causative mechanisms.
- To correlate theoretical findings with experimental observations in paced animal hearts.
Main Methods:
- Utilized mathematical modeling to simulate cardiac cell dynamics and alternans formation.
- Employed optical mapping techniques to record membrane voltage (V(m)) and intracellular calcium (Ca(i)) in paced rabbit hearts.
- Analyzed spatial patterns of alternans to identify dynamic versus heterogeneity-driven mechanisms.
Main Results:
- Mathematical models demonstrated that dynamic changes in alternans spatial patterns can effectively pinpoint underlying mechanisms.
- Optical mapping of V(m) and Ca(i) in rabbit hearts showed that rapid pacing-induced discordant alternans align with purely dynamical mechanisms.
- The study provides evidence that spatially discordant alternans can emerge from dynamical pattern formation without requiring tissue heterogeneity.
Conclusions:
- Dynamic pattern formation is a viable mechanism for generating spatially discordant alternans in the heart.
- Mathematical modeling combined with optical mapping offers a powerful approach to elucidate cardiac alternans mechanisms.
- These findings challenge the necessity of tissue heterogeneity for discordant alternans initiation, suggesting dynamical processes play a key role.
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