Noninvasive ECG imaging of electrophysiologically abnormal substrates in infarcted hearts - A model study

Background-Myocardial infarction and subsequent remodeling create substrate s with altered electrophysiological (EP) properties that are highly arrhyth mogenic. Existing ECG methods cannot always detect the existence of such su bstrates nor provide any detailed information about their EP characteristic s. A noninvasive method with such capabilities is greatly needed for identi fying patients at risk of arrhythmias and for guidance and evaluation of th erapy. Recently, we developed a noninvasive ECG imaging modality that can r econstruct epicardial EP information from body surface potentials. We exten ded its application to hearts with structural disease and examined its abil ity to detect and characterize abnormal EP substrates. Methods and Results-Epicardial potentials were recorded with a 490-electrod e sock from an open-chest dog. Recordings were obtained from a normal heart and from the same heart 2 hours after left anterior descending coronary ar tery occlusion and ethanol injection to create an infarct. Body surface pot entials were generated from these epicardial potentials in a human torso mo del. Realistic geometry errors and measurement noise were added to the tors o data, which were then used to noninvasively reconstruct epicardial potent ials and electrograms (EGMs), with excellent accuracy. EP characteristics a ssociated with the infarct substrate were reconstructed, including (1) a ne gative region over the infarct, (2) EGMs with large predominant negative de flections (eg, Q-wave EGMs), (3) Q-wave EGMs with superimposed RS deflectio ns reflecting local activation of surviving myocardium within the infarct b order zone, (4) reduced magnitudes of EGM negative derivatives, and (5) neg ative QRS integrals of EGMs over the infarct. Conclusions-ECG imaging can noninvasively detect and map abnormal EP substr ates associated with infarction and structural heart disease.