A Simulation Study of the Single Moving Dipole Representation of Cardiac Electrical Activity

A simulation study of the accuracy of the single moving dipole (SMD) cardiac representation was done using a realistic computer model of the human torso. This model included regions of different electrical conductivities such as the lungs and the intraventricular blood masses. Dipolar potential distributions generated on the surface of this model were sampled with different electrode arrangements and were subsequently contaminated with random noise. The location, magnitude, and orientation of the SMD which optimally fitted these potentials were then compared to those of the original dipole source in order to assess the errors in the SMD parameters. The SMD computations were based on a least squares estimation of a variable number of multipolar components recovered inside a torso model which was either finite and homogeneous or finite with lungs. The results showed that the SMD accuracy can be significantly improved by adding higher order multipolar components, e.g., with 120 electrodes and the absence of noise, the rms position error was 15.5 mm with eight multipoles and 0.6 mm with 24 multipoles when the same homogeneous model was used for both the simulation and the recovery. It was also shown that the addition of lungs in the recovery model permitted a higher accuracy when either the lungs, or the lungs with blood masses, were present when the dipolar potential distributions were generated; for these two cases, the rms position errors were thus 1.7 and 4 mm, respectively, using 120 electrodes and 24 multipoles in the absence of noise.