Imaging dispersion of myocardial repolarization, II - Noninvasive reconstruction of epicardial measures

Background-Dispersion of myocardial repolarization supports the development and maintenance of life-threatening arrhythmias. Current noninvasive appro aches for detecting substrates with increased dispersion based on ECG measu res (eg, QT dispersion) have shown limited success and inconsistencies. The companion article shows that, in contrast, epicardial potentials and deriv ed measures reflect local dispersion of repolarization. Here, using a recen tly developed ECG imaging method, we evaluate the feasibility of noninvasiv e reconstruction of such epicardial measures from body-surface ECG data. Methods and Results-Epicardial potentials were recorded with a 224-electrod e sock from an open-chest dog during control, regional warming, cooling, an d simultaneous adjacent warming and cooling to induce localized changes in myocardial repolarization and regions of increased dispersion. Body-surface potentials were generated from these epicardial potentials in a human tors o model. Realistic geometric errors and measurement noise were added to the torso data, which were then used to noninvasively reconstruct epicardial m easures of repolarization dispersion (activation recovery intervals [ARIs] and QRST integrals). Repolarization properties were accurately depicted by ECG imaging including (1) shortened ARIs and increased QRST integrals over the warmed region, (2) prolonged ARIs and decreased QRST integrals over the cooled region, and (3) high gradients of ARIs and QRST integrals over the adjacent warmed and cooled regions. Conclusions-ECG imaging can reconstruct repolarization properties accuratel y and localize areas of increased dispersion of repolarization in the heart noninvasively. Its clinical significance lies in the possibility of noninv asive risk stratification and in guidance and evaluation of therapy.