Electroanatomic mapping of the right atrium. The upper panels present the right lateral voltage map for each of the five patients. Voltage range is from 0.03/0.05 mV to 0.5 mV. Note that all five maps demonstrate an extensive LVZ occupying virtually the entire RA free wall from the crista terminalis posteriorly to the tricuspid annulus anteriorly. Superiorly the LVZ reaches the superior RA and inferiorly merges with the inferior vena cava. The purple and pink dots in the left most panel indicate sites of complex electrograms and the red dots in the middle panel indicate ablation points. The lower panels show representative electrogram examples from within the LVZ using either the pentaray (A–C panels) or the orion (D and E panels) mapping catheters. Recordings are made during sinus rhythm or atrial pacing with the exception of the middle panel (C), which demonstrates electrograms during an unstable atrial arrhythmia. Note the low amplitude, multi-component complex electrograms. There are also some channels with no recordable near field electrograms despite adequate tissue contact indicating regions of scarring. LVZ, low-voltage zone; HBE, His bundle electrogram; CS, coronary sinus; RA, right atrium.