Fitting the foot current

See code in GitLab.
Author: Cristian Barrios Espinosa cristian.espinosa@kit.edu

Finding Ifoot Parameters

Reaction eikonal simulations in openCARP are used to fit the parameters for the Ifoot current, which is essential to trigger the action potential [Neic2017]. The choice of parameters depends on the ionic model used, offering a computationally efficient way to calculate activation times from electrical wave propagation in cardiac tissue. These simulations do not model transmembrane voltage dynamics, making them ideal for fast approximations or pre-analysis steps.

To run the experiments described in this tutorial, navigate to the following directory:

cd ${TUTORIALS}/03_Eikonal/04_Fit_Ifoot

Simulation Setup

To find the best fit for the Ifoot parameters, a monodomain simulation is first run using the desired ionic model and its parameters in a 3D block. The threshold voltage, V_th, must be provided. This threshold represents the minimum transmembrane voltage required to trigger an action potential, typically linked to the sodium channels' activation threshold, although more phenomenological models may adopt a simplified formulation.

python3 ./run.py --help
...
Tutorial specific options:
--imp IMP              Ionic Model to optimize. (default: Courtemanche)
--model_par MODEL_PAR   Ionic Model parameters. (default: )
--V_th V_TH             Voltage threshold for the cutoff of the foot current (mV). (default: -30)

Experiments

Experiment 1: Find the Ifoot parameters for the Courtemanche model (default)

The first experiment finds the Ifoot parameter for the Courtemanche model with default parameters [Courtemanche1998].

python3 run.py

The output will provide the fitted parameters for the Ifoot model corresponding to the ionic model used, as well as the error of the fit:

Fitted A_F: 2.464218456421841
Fitted tau_F: 0.43917740479584627
RMSE: 0.687515024630087

Experiment 2: Find the Ifoot parameters for the OHara-Rudy model

In this case, we change the ionic model and find the Ifoot parameters for the default set of parameters of [OHara2011].

python3 run.py --imp OHara

The result should provide the fitted parameters as well:

Fitted A_F: 3.007586177286489
Fitted tau_F: 0.3141233370949477
RMSE: 2.3670844102567106

Experiment 3: Change model parameters

Modify the parameters of the Courtemanche model to simulate atrial fibrillation, as described by [Loewe2016].

run.py --model_par 'GCaL*0.45,GK1*2,GNa*1,factorGKur*0.5,Gto*0.35,GKs*2,maxIpCa*1.5,maxINaCa*1.6'

The output should give the following result:

Fitted A_F: 4.025919988860185
Fitted tau_F: 0.4572368218676241
RMSE: 0.821926533960846

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