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Figure 5.14. Guidance of CRT lead placement with ECGI. ECGI activation maps for five pacing
regimes Pre-CRT, CRT-OPT, CRT-NOM, ANT-P, POST-P are shown in two views, anterior (left) and
inferior (right). This patient is an eight years old male with hypoplastic left heart syndrome, mitral
atresia, and double outlet right ventricle, who had a DDD epicardial pacemaker implanted at the
age of three months for postoperative complete heart block. The pacing lead was placed in a right
posterior area (white asterisk, Pre-CRT panel). At four years of age, he had a fenestrated extra-
cardiac Fontan operation. Over the following several years, he developed worsening HF. His
Pre-CRT activation map (top panel) showed a severely elevated electrical dyssynchrony index
(ED =50 ms; see text below for ED definition), with severely delayed activation of the left anterior
basal and inferior basal areas of the ventricle (dark blue, Pre-CRT). These areas were designated as
suitable sites for the resynchronization lead. The patient underwent surgical implant of an
epicardial lead at the left anterior basal area. Repeated ECGI three months after implant and
onset of CRT pacing showed a dramatically improved synchrony during optimal BiV pacing, with
ED dropping to the normal range (ED =27 ms, CRT-OPT ). Improvement with nominal BiV pacing
(without optimization of interventricular pacing delay) was slightly less (ED =29 ms, CRT-NOM).
ANT-P and POST-P: single lead anterior and posterior pacing, respectively. White asterisks denote
sites of pacing leads. From Silva et. al. [307] with permission of Elsevier.

(dark blue, top row) that was present during native rhythm. LV activation was more synchronized
during CRT, with the latest activation reduced from 174 ms to 138 ms and covering a much smaller
region of the LV. In patient #3 (panel B) the lead placement was at the anterior LV. Activation from

the pacing electrode (asterisk in bottom row) captured the LV, eliminating the very late activation
region (173 ms, top row). A new line of block formed on the antero-lateral surface, forcing the wave
front to pivot around it and activate the lateral basal LV last, at 117 ms.