how do calcium and potassium conductance affect atrial fibrillation? fluctus (group 3) maisam t....

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: GCaL

• Potassium conductance: GKs

L Type Calcium Channels

• Generates inward Calcium current (ICaL).• Depolarizes cell.

Potassium Channels

• Generates outward Potassium current.• Hyperpolarizes cell.

• Includes slow outward Potassium current (IKs).

http://www.nature.com/nature/journal/v451/n7181/fig_tab/nature06799_F2.html

http://www.cvpharmacology.com/antiarrhy/cardiac_action_potentials.htm

Hypothesis

• Increasing GCaL would increase ICaL 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%

GCal

GKs

Results

Loop & Hook

GCaL= 65% GKs= 145%

Drift

GCaL= 125% GKs= 85%

Spin

GCaL= 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.