Impact of Electrode Type on Mapping of Scar-Related VT : Mapping of Scar-Related VT

Patients with nonischemic left ventricular cardiomyopathy (LVCM) and ventricular tachycardia (Vt) have complex 3-dimensional substrate with variable involvement of the endocardium (ENDO) and epicardium (EPI). The purpose of this study was to determine whether ENDO unipolar (UNI) mapping with a larger electric field of view could identify EPI low bipolar (BIP) voltage regions in patients with LVCM undergoing Vt ablation. The reference value for normal ENDO unipolar voltage was determined from 6 patients without structural heart disease. Consecutive patients undergoing Vt ablation over an 8-year period with detailed (>100 points) LV ENDO and EPI mapping and normal LV ENDO BIP voltage were identified. From this cohort, we compared patients with structurally normal hearts and normal EPI BIP voltage (EPI-, group 1) with patients with LVCM and low LV EPI BIP voltage regions present (EPI+, group 2). Confluent regions of ENDO UNI and EPI BIP low voltage (>2 cm(2)) were measured. The normal signal amplitude was >8.27 mV for LV ENDO UNI electrograms. Detailed LV ENDO-EPI maps in 5 EPI- patients were compared with 11 EPI+ patients. Confluent ENDO UNI low-voltage regions were seen in 9 of 11 (82%) of the EPI+ (group 2) patients compared with none of 5 EPI- (group 1) patients (P<0.001). In all 9 patients with ENDO UNI low voltage, the ENDO UNI low-voltage regions were directly opposite to an area of EPI BIP low voltage (61% ENDO UNI-EPI BIP low-voltage area overlap). EPI arrhythmia substrate can be reliably identified in most patients with LVCM using ENDO UNI voltage mapping in the absence of ENDO BIP abnormalities.

The resolution of mapping is influenced by electrode size and interelectrode spacing. Smaller electrodes with closer interelectrode spacing may improve mapping resolution, particularly in scar. The aims of this study were to establish normal electrogram criteria in the atria for both 3.5-mm electrode tip linear catheters (Thermocool) and 1-mm multielectrode-mapping catheters (Pentaray) and to compare their mapping resolution in scar-related atrial arrhythmias.

The risk and success of epicardial substrate ablation for ventricular tachycardia (VT) support the value of techniques identifying the epicardial substrate with endocardial mapping. The purpose of this study was to test the hypothesis that endocardial unipolar voltage mapping in patients with right ventricular (RV) VT and preserved endocardial bipolar voltage abnormalities might identify the extent of epicardial bipolar voltage abnormality. Using a cutoff of < 5.5 mV for normal endocardial unipolar voltage derived from 8 control patients without structural heart disease, 10 patients with known ARVC/D (group 1, retrospective) and 13 patients with RV VT (group 2, prospective) with modest or no endocardial bipolar voltage abnormalities underwent detailed endocardial and epicardial mapping. The area of epicardial unipolar voltage abnormality in all 10 group 1 patients with ARVC/D (62 ± 21 cm²) and in 9 of the 13 group 2 patients (8 with criteria for ARVC/D) (53 ± 21 cm²) was on average three times more extensive than the endocardial bipolar abnormality and correlated (r = 0.63, P <.05 and r = 0.81, P <.008, respectively) with the larger area epicardial bipolar abnormality with respect to size (group 1: 82 ± 22 cm²; group 2: 68 ± 41 cm²) and location. In the remaining 4 group 2 patients and 3 additional reference patients without structural heart disease, endocardial bipolar, endocardial unipolar, and, as predicted, epicardial bipolar voltage all were normal. Endocardial unipolar mapping with cutoff of 5.5 mV identifies more extensive areas of epicardial bipolar signal abnormalities in patients with ARVC/D and limited endocardial VT substrate. Copyright © 2011 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.