Rhythm during voltage assessment
The majority of VGA studies have undertaken substrate assessment in
sinus rhythm. It remains uncertain how adequately voltage mapping in
regular rhythms highlight areas involved in AF perpetuation. For
example, both LVAs and regions harboring electrogram fractionation when
mapped in AF, often display more normal parameters when reassessed in SR
(115). This rhythm-dependent variability in electrogram size and
morphology likely represents functional properties of the tissue, which
may harbor arrhythmogenic potential. At lower rates of activation in
regular rhythms, such diseased tissue may not be under sufficient
physiological stress, and appear ‘normal’. Rapid activation, such as in
AF, may exceed the functional reserve of the tissue and manifest as
lower bipolar voltages and/or fractionated signals. These functional
properties may be exploited through pacing protocols to identify
arrhythmogenic sites, when mapping is performed in sinus rhythm or
coronary sinus pacing.