A model of thorax conductivities and a model of the cardiac generator is required for the ECG inverse problem. 
ECG inverse problem
Comparison of minimum-norm estimation and beamforming in electrocardiography with acute ischemia.In the electrocardiographic (ECG) inverse problem, the electrical activity of the heart is estimated from measured electrocardiogram. 
minimum-norm estimation
Comparison of minimum-norm estimation and beamforming in electrocardiography with acute ischemia.In the electrocardiographic (ECG) inverse problem, the electrical activity of the heart is estimated from measured electrocardiogram.  In this work, we focus on two methods for solving the inverse problem of ECG in the case of acute ischemia: minimum-norm (MN) estimation and linearly constrained minimum-variance beamforming. 
beamforming