A noninvasive imaging modality for cardiac arrhythmias

Abstract

Background: The last decade witnessed an explosion of information regarding the genetic, molecular, and mechanistic basis of heart disease. Translating this information into clinical practice requires the development of novel functional imaging modalities for diagnosis, localization, and guided intervention. A noninvasive modality for imaging cardiac arrhythmias is not yet available. Present electrocardiographic methods cannot precisely localize a ventricular tachycardia (VT) or its key reentrant circuit components. Recently, we developed a noninvasive electrocardiographic imaging modality (ECGI) that can reconstruct epicardial electrophysiological information from body surface potentials. Here, we extend its application to image reentrant arrhythmias.

Methods and results: Epicardial potentials were recorded during VT with a 490 electrode sock during an open chest procedure in 2 dogs with 4-day-old myocardial infarctions. Body surface potentials were generated from these epicardial potentials in a human torso model. Realistic geometry errors and measurement noise were added to the torso data, which were then used to noninvasively reconstruct epicardial isochrones, electrograms, and potentials with excellent accuracy. ECGI reconstructed the reentry pathway and its key components, including (1) the central common pathway, (2) the VT exit site, (3) lines of block, and (4) regions of slow and fast conduction. This allowed for detailed characterization of the reentrant circuit morphology.

Conclusions: ECGI can noninvasively image arrhythmic activation on the epicardium during VT to identify and localize key components of the arrhythmogenic pathway that can be effective targets for antiarrhythmic intervention.

Figure 1

Anterior view of activation isochrones during 2 cycles of VT. Isochrones are presented for each cycle, with color legend (time in ms) displayed below. The right ventricle (RV), LAD, and left ventricle (LV) are labeled. Lines of block are drawn in black. ECG lead II is shown, with vertical lines indicating time frames displayed for each cycle. Top, Isochrones from first VT cycle. Bottom, Isochrones from second VT cycle. Left, Measured isochrones. Right, Noninvasively reconstructed isochrones. Arrows indicate direction of wavefront propagation. An animated version of this figure can be found at www.circulationaha.org

Figure 2

Epicardial electrograms during 2 cycles of VT. Anterior and posterior views of heart are shown. Letters in boxes identify sites where measured and noninvasively reconstructed electrograms are displayed. Solid black lines estimate location of CCP. Electrograms are shown in pairs, with measured electrograms on left and noninvasively reconstructed electrograms on right. Sites A through C are from CCP, D through F are from anterior left ventricle (LV), G through I are from anterior right ventricle (RV), J and K are from the posterior left ventricle, and L is from posterior right ventricle. CC indicates correlation coefficient between noninvasively reconstructed and measured electrograms.

Figure 3

Potential maps during VT. Potentials are displayed as contour maps, with negative regions shaded red to green and positive regions shaded green to blue. Estimated wavefront locations are shown with arrows. A, 5 ms wavefront entering CCP. Left, Anterior view of torso. Middle, Anterior view of measured epicardial potentials. Right, Anterior view of noninvasively reconstructed epicardial potentials. Bottom, ECG lead II is shown, with arrow indicating time frame presented. B, 50 ms wavefront exiting CCP. C, 105 ms wavefront forming arms of reentrant circuit.