Model-based control of cardiac alternans on one dimensional tissue
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Garzon, Alejandro
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Abstract
When excitable cardiac tissue is electrically paced at a sufficiently
high rate, the duration of excitation can alternate from beat to beat
despite a constant stimulation period. This rhythm, known as alternans,
has been identified as an early stage in a sequence of increasingly complex
instabilities leading to the lethal arrhythmia ventricular fibrillation (VF).
This connection served as as a motivation for research into the control of
alternans as a strategy to prevent VF. Control methods that do not use a model
of the dynamics have been used for the suppression of alternans. However, these
methods possess limitations.
In this thesis we study theoretically model-based control techniques with the goal
of developing protocols that would overcome the shortcomings of non model-based
approaches. We consider one dimensional tissue in two different geometrical configurations:
a ring and a fiber with free ends (open fiber). We apply standard control methods for
linear time invariant systems to a stroboscopic map of the linearized dynamics around
the normal rhythm. We found that, in the ring geometry, model-based control is able to
suppress alternans faster and with lower current, thereby reducing the risk of tissue damage,
compared with non-model-based control. In the open fiber, model-based control is able to
suppress alternans for longer fibers and higher pacing frequencies in comparison
with non-model-based control. The methodology presented here can be extended to
two- and three-dimensional tissue, and could eventually lead to the suppression
of alternans on the entire ventricles.
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Date
2010-08-24
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Dissertation