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How do Calcium and Potassium conductance affect atrial fibrillation? Fluctus (Group 3) Maisam T. Begum Joshua Finer Peter Valdez
Atrial Fibrillation • Over 2. 2 million people in the US have atrial fibrillation (8 - 9% of people over 80). • Blood clots can form, leading to a stroke. • Some symptoms include irregular heart beats, chest pain, and shortness of breath. • Still not well understood.
TNNP Model • Based on experimental data. • Attempts to more accurately represent the action potential than other models by including more than a minimal number of parameters. • Computationally tractable (especially with progress in GPUs).
Conductance • Calcium conductance: GCa. L • Potassium conductance: GKs
L Type Calcium Channels • Generates inward Calcium current (ICa. L). • Depolarizes cell. Potassium Channels • • • Generates outward Potassium current. Hyperpolarizes cell. Includes slow outward Potassium current (IKs).
http: //www. nature. com/nature/journal/v 451/n 7181/fig_tab/nature 06799_F 2. html
http: //www. cvpharmacology. com/antiarrhy/cardiac_action_potentials. htm
Hypothesis • Increasing GCa. L would increase ICa. L and make the spiral wave thicker. • Increasing GKs would increase IKs and make the spiral wave thinner.
Methods • Parameter Range: 25% - 185% • Parameter Increment: 20% GKs GCal
Loop & Hook GCa. L= 65% GKs= 145%
Drift GCa. L= 125% GKs= 85%
Spin GCa. L= 65% GKs= 65%
Discussion/Conclusion • Our hypothesis was wrong since many of the spiral waves looked very similar. • It is difficult to draw a conclusion since many of the spirals looked very similar. • We think there might be a well-defined pattern of the spiral wave tip path.
Future Work • Repeat simulations (with slight variations). • Change more than 2 parameters at a time. • Include the graphs of how membrane potential changes over time. • Look at single individual periods.
Acknowledgments • A special thanks to Dr. Griffeth, Dr. Fenton, Aron, Chuck, Rachel, Dan and CMACS.