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Figure 5.4. Epicardial potentials during normal Before Breakthrough
ventricular activation. Data in A to D are from
one representative subject. A. At 5ms before
RV breakthrough. The cartoon (right) shows
the intramural activation wave front,
represented by a layer of dipoles approaching
the RV epicardium and generating positive
potentials (+). At this time, positive
potentials cover the RV epicardium (left; red).
B. RV breakthrough. The cartoon (right) shows
the wave front breaking on the RV epicardium.
The dipoles diverge, generating negative Right ventricular breakthrough
potentials on the epicardium (-). The ECGI
reconstructed epicardial potentials show a
localized intense negative minimum
(left; dark blue) at the breakthrough site.
C. Mid-QRS, 40 ms after QRS onset. Multiple
breakthrough minima are observed (dark blue,
marked 1 to 4). A broad maximum covers the
LV apex. D. Late QRS, 60ms after QRS onset.
RV is covered by negative potentials.
The LV maximum has extended toward
the posterolateral base. E. A summary of
breakthrough locations in seven subjects.
The numbers indicate how many subjects
had breakthrough at each site. Note that all
seven subjects had the earliest RV break-
through. From Ramanathan et. al. [286]
courtesy of Proceedings of the National
Academy of Sciences (PNAS).

Summary of Epicardial Breakthroughs