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Noninvasive electrocardiogram imaging of substrate and intramural ventricular tachycardia in infarcted hearts

^a Cardiac Bioelectricity Research and Training Center (CBRTC) and the Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
^b Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah, USA

View larger version (36K): [in a new window]   Figure 1 (A) Estimated location and extent of electrophysiologically abnormal substrate due to infarction. The epicardium is displayed in three partially overlapping views, viewed from the right posterolateral, anterior and left posterolateral aspects of the torso. The right ventricle (RV) and left ventricle (LV) are labeled. The left anterior descending coronary artery (LAD) and posterior descending coronary artery (PDC) are shown as thick black lines. Gray regions outlined by solid lines define regions with pure Q-wave electrograms during right atrium (RA) pacing. Gray regions outlined by dashed lines define regions with Q-wave electrograms containing superimposed sharp deflections indicating islands of local activation. Representative electrograms during RA pacing are shown on the heart to illustrate the electrogram morphologies in each region. The horizontal dashed black line marks the estimated level of the tissue slice presented in Figures 2 and 4. Top row shows measured data. Bottom row shows noninvasively reconstructed data. (B) Shows electrograms from approximately corresponding locations measured by epicardial-sock electrodes in direct contact with the epicardium (left) and by rod-tip electrodes on the epicardial envelope (right). Numbers correspond to the numbered locations on the heart views in (A).

View larger version (63K): [in a new window]   Figure 2 Epicardial electrograms during right atrium pacing. A stained tissue slice is shown to orient sites A to L, where epicardial electrograms were directly measured and noninvasively reconstructed. The anterior, left, posterior and right labels are in reference to the heart oriented in the torso. The locations of the right ventricle (RV), left ventricle (LV) and infarct (light brown) are indicated. Measured electrograms are plotted in red and noninvasively reconstructed electrograms in blue.

View larger version (65K): [in a new window]   Figure 3 Activation isochrones for three consecutive cycles of ventricular tachycardia (VT). Isochrones are presented for each cycle, with the color legend (time in ms) displayed below (earliest activation is dark blue). White arrows indicate direction of wavefront propagation. Regions where no activation times were assigned because of small magnitude/–time of maximum negative derivative are shown as gray. Electrocardiogram lead II is shown with vertical blue lines indicating the time frames displayed for each cycle. (A) Isochrones from VT cycle 1. Top row shows measured isochrones. Bottom row shows noninvasively reconstructed isochrones. (B) Isochrones from VT cycle 2. (C) Isochrones from VT cycle 3. LAD = left anterior descending coronary artery; PDC = posterior descending coronary artery.

View larger version (58K): [in a new window]   Figure 4 Epicardial electrograms during reentry; same format as Figure 2. White arrows indicate direction of proposed wavefront propagation. Horizontal bars on electrograms mark activation times at each site for the measured (red) and noninvasively reconstructed (blue) signals. Green electrograms at the bottom are recorded from the epicardial sock at about the same locations as rod-tip electrograms G to J. LV = left ventricle; RV = right ventricle.

View larger version (86K): [in a new window]   Figure 5 Epicardial potential maps during epicardial breakthrough. Potentials are displayed as color-coded maps. In each panel, measured potentials are on the left, and noninvasively reconstructed potentials are on the right. (A) Potentials corresponding to right atrium (RA) pacing (simulated sinus rhythm). The numbers mark the locations of the three epicardial breakthroughs. (B to G) Potentials corresponding to ventricular tachycardia (VT) cycles 1, 2, 3, 5, 8 and 9, respectively. *Locations of epicardial breakthroughs for each VT cycle. The distances between the measured and reconstructed breakthrough sites (d) are provided.