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.