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4. Atrial Flutter (Ramanathan, Nature Medicine 2004; 10:22) 278 . ECGI reconstructed the

right atrium reentry circuit of typical atrial flutter and the atrial activation pattern driven by
this circuit. The maps were consistent with observations from direct mapping of typical
atrial flutter using intra-cardiac catheters.

5. Focal Atrial Tachycardia (Wang, Heart Rhythm 2007; 4:1081) 285 . ECGI located the focal
source on the roof of the left atrium, between the right superior pulmonary vein and atrial
septum. Invasive right and left atrial electroanatomic catheter mapping identified a focal
tachycardia originating from the superior left atrium between the right superior pulmonary

vein and atrial septum, confirming the ECGI determination. The tachycardia was terminated
with application of RF energy to this location.

Normal Excitation (Ramanathan, Nature Medicine 2004;10:22 278 and Ramanathan, PNAS

2006;18:6309 286 )

ECGI mapping of atrial and ventricular activation was conducted in 7 normal subjects under
complete physiological conditions. Results are in close agreement with those recorded directly in

7 isolated non-diseased human hearts in the classic study by Durrer et al 287 , including areas of early
activation, epicardial breakthrough sites, the general activation sequence and regions of latest
activation. The locations of epicardial breakthrough sites were in agreement with those observed
in an intraoperative study by Wyndham et al 288 . A later study of 20 normal volunteers combined

ECGI and tagged MRI (Andrews, Circ Arrhythm Electrophysiol. 2019;12:e007484) 289 to study the
electromechanics of the normal human heart. The ECGI maps in this study were consistent with
the previous studies referenced above.

5.3 Activation and Repolarization of the Normal Human Heart 278, 286, 289

Normal Atrial Activation

Figure 5.2 shows isochrones for normal atrial activation during sinus rhythm. Top: Non-
invasive ECGI reconstructed isochrones maps from two healthy volunteers. Bottom: Isochrones
recorded directly from an isolated non-diseased human heart, shown here for comparison.

Earliest activation (dark red) starts in the right atrium (RA) near the root of the aorta, at the
anatomic location of the sinoatrial (SA) node, where the impulse originates. It then propagates
radially to the rest of the RA and the left atrium (LA). The LA appendage is the last area to activate
(dark blue). The noninvasively reconstructed isochrones (top panels) are consistent with those

measured directly (bottom panel). Note that the anatomic location of impulse generation varies
between the two ECGI maps; it is more inferior in the map on the left. This observation is consistent
with the anatomical structure of the SA node, which extends inferiorly towards the atrioventricular
(AV) node.