Page 153 - YORAM RUDY BOOK FINAL

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Figure 5.16. Activation maps
from two patients who have
not responded to CRT. Native
rhythm (top) and BIV pacing
(bottom) maps are shown for
each patient. Format is similar
to Figure 5.13. Pacing sites are
marked by asterisks. From
Jia et. al. [304] with permission
of Elsevier.

important observation is the completely normal activation of the RV. This suggests that CRT can

be achieved by LV pacing alone, through fusion between the normal RV native activation and the
paced LV activation. An example of this strategy is shown in Figure 5.17.

Evaluating Synchrony with ECGI 308, 308a

The spatial-temporal relationships between excitation in different regions of the ventricles deter-
mines the degree of cardiac synchrony. The body-surface ECG reflects global ventricular activation
and its ability to determine synchrony is limited. The ECG QRSd has been used as a measure of

synchrony with limited success. Unlike the ECG, ECGI maps regional activation in the heart and
the spatial-temporal relationships between activation of different cardiac regions. Hence, ECGI
can measure the degree of cardiac synchrony directly and noninvasively. Taking advantage of this

capability, we defined an electrical dyssynchrony index (ED) of LV activation as the standard