IMPACT OF THE TORSO MODEL ON THE INVERSE LOCALIZATION OF ISCHEMIA

In this simulation study the accuracy of the inverse localization of an ischemic lesion was investigated if a patientadjusted general torso model and four different approximate heart models were used. Surface ECGs were simulated by a normal heart and by hearts with 18 different ischemic lesions in 7 realistic torso models. Position of each lesion represented by a single dipole was then searched by an inverse solution. Difference QRST integral maps reflecting differences between cardioelectric fields of the ischemic and normal hearts were used. With a standard heart model the mean error of the lesion localization was 3.4 cm. With a standard heart model shifted to an inversely estimated position this error was 3.9 cm, for an equally shifted and properly formed and rotated heart model the error was 2.4 cm and for a heart model properly shifted, formed and rotated the error was 1.1 cm. If realistic CT or MRI-based torso model was used the lesion localization error was 0.7 cm. From the results it can be concluded that use of adjusted standard torso model with properly positioned and formed standard heart model can lead to acceptable accuracy of the inverse localization of an ischemic lesion

Impact of the patient torso model on the solution of the inverse problem of electrocardiography

Cardiac diagnostics based on a solution of the inverse problem of electrocardiography offers new tools for visual assessment of cardiac ischemia. The accuracy of the inverse solution is influenced by fidelity of the patient torso model. As optimum, an individual torso model with real heart shape and position obtained from CT or MRI is desirable. However, imaging is not always available in clinical practice, hence we investigated, if a generic torso shape individually adjusted according to patient†s chest dimensions, with a simplified heart model placed to a vertical position obtained from inverse localization of the early ventricular activation can result in an inverse solution close to the result obtained with an accurate torso model. Simulated inverse localization of 18 ischemic lesions for 9 subjects showed that the use of individually adjusted generic torso instead of real torso shape led to an acceptable increase of the lesion localization error from 0.7±0.7 cm to 1.1±0.7 cm when accurate heart model was used. However, if simplified heart model was used and placed in a vertical position according to the V2 lead level, the lesion localization error increased to 3.5±0.9 cm. Moving the simplified heart model to a position estimated by the inverse solution decreased the vertical heart positioning error from 1.6±2.3 cm to 0.2±1.2 cm but without adjusting the heart shape and rotation the lesion localization error did not improve and reached 3.7±1.0 cm