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400,000 Americans die suddenly each year
from heart diseases |
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About every 29 seconds someone suffers
from a coronary event |
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Every 60 seconds, someone DIES!!!!! |
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Excitable medium |
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Limit-cycle oscillators |
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Catheter stimulation |
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Reentrant Tachycardia |
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MAIN IDEA: Building case to support new
model vs. old model of dynamics of healthy/dying heart |
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Could be useful in PREDICTING, have we
gotten to understanding? |
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Arrhythmias, tachycardias, flutters,
fibrillations |
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Idea that modeled fibrillation is chaotic
process |
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Feigenbaum-type period doubling |
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Erratic-looking |
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The dying heart is a periodic process |
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Healthy cardiac dynamics are chaotic
(variable) |
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“Sudden death, therefore, may be viewed
as a bifurcation out of, not into chaos.” |
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Inverse Bifurcation |
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Made from observations of a healthy human
heart |
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Broadband spectra from EKG data (1/f-like,
indicates activation of graphical fractal network) |
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Phase-space plots of heart rate/heart
rate delays indicate strange-like attractors |
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Observed characteristics from a dying
heart |
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Narrow spectra |
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Electrophysiological recording of inner
& outer surfaces = periodic |
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Low frequency oscillations |
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Phase-space plot of heart rate/heart
rate delay show not much variation |
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Determining if chaos can be applied |
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If yes, then apply it |
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Aim for unstable lower order rhythms |
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MAIN IDEA: Using experimental model,
simulate cardiac arrhythmias and use chaos theory to alter beats
and restore periodic beating. |
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Since chaotic systems are sensitive to
initial conditions, invokes big change |
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Interventricular septum cells from rabbit
in solution hooked up to monitor electrical impulses |
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Introduction of arrhythmias with ouabain
(creates oscillations in intracellular calcium & initiates
sporadic beating) |
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Develop model, identify parameters, tweak
parameters |
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Initially characterized by a constant
interbeat interval (period 1) |
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Moved to period 2 |
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Moved to period 4 |
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Aperiodic, but chaotic (set of points,
not space-filling) |
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Views arrhythmias at point in which interbeat
intervals are aperiodic |
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Line of indentity, fixed point |
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Divided into learning phase and intervention
phase |
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Equation |
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Control of scroll waves |
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Clinical control of spiral waves |
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Notes