Multielectrode mapping may be more effective than point-by-point mapping for VT substrate ablation

Ventricular Arrhythmia Research Group (from left to right): First row: José Ortiz, Elena Arbelo, Antonio Berruezo, Mario Cabrera. Second row: Francesca Vassanelli, David Soto, Mikel Martinez , Juan Acosta. Third row: Diego Penela, Markus Linhart.

Results from the first randomised study comparing multielectrode mapping vs. conventional point-by-point mapping for ventricular tachycardia (VT) substrate ablation procedures have shown that a multielectrode mapping strategy allows better discrimination of local abnormal electrograms and conducting channels, which may be considered key elements for successful VT substrate ablation.

The study, recently published in Europace by the Ventricular Arrhythmia Research Group, Barcelona, Spain, led by Antonio Berruezo (Hospital Clinic and IDIBAPS, Barcelona, Spain), also found that ablation guided by multielectrode mapping was associated with a shorter radiofrequency time.

“Current VT substrate ablation strategies aim to completely abolish abnormal local electrograms identified within the scar region. Therefore, substrate-based approaches are highly dependent on accurate delineation of scar architecture and identification of abnormal local electrograms,” write the researchers. Point-by-point electroanatomical mapping is the “conventional strategy” used to identify slow conducting channels that are ablation targets; however, this strategy is “time consuming and operator dependent” as it requires a very detailed and accurate electroanatomical map, the authors comment.

Multipolar catheters with smaller electrodes and shorter interelectrode distances “may facilitate” the detection of such areas of slow conduction, the researchers argue; therefore, they sought to compare multielectrode mapping using the PentaRay catheter (Biosense Webster) vs. conventional point-by-point mapping using the open irrigated 3.5mm tip Thermocool Navistar catheter (Biosense Webster) in a first-of-its-kind randomised study.

From September 2013 to December 2015, 20 consecutive patients (95% male, 67.3±10.3 years old) with ischaemic heart disease undergoing VT ablation were enrolled at Hospital Clinic and IDIBAPS, Barcelona, Spain. The patients were randomised into two groups. In group A (10 patients), substrate mapping was performed first by point-by-point mapping (PPM) and second by multielectrode mapping (MEM), ablation was guided by PPM. In group B (10 patients), substrate mapping was performed first by MEM and second by PPM, ablation was guided by MEM.

The researchers identified that by using MEM the far-field/late potential ratio was significantly lower compared to PPM (0.58±04 vs. 1.64±1.1; p=0.01), which provided better discrimination of local abnormal electrograms and conducting channels. “Multielectrode catheters (such as PentaRay) with smaller electrode size and closer interelectrode distance may provide a better resolution of intracardiac electrocardiograms than conventional mapping catheters, allowing more accurate assessment of the activation sequence within the conducting channels and better identification of the conducting channels entrance,” the authors note.

Results also showed that scar dechanneling guided by MEM was associated with a shorter radiofrequency time (median 12 vs. 22 minutes; p=0.023). This could be due to a “better identification of appropriate ablation targets” with this strategy, the researchers highlight.

“It should be noted that the ablation technique used in this study (scar-dechanneling) aims complete arrhythmic substrate elimination by selectively targeting conducting channel entrances. Thus, the appropriate identification of ablation targets becomes a key point when using this ablation approach,” the Ventricular Arrhythmia Research Group write.

Amongst other results the researchers found that substrate mapping time was similar with MEM and PPM (19.7±7.9 minutes vs. 25±9.2 minutes p=0.222) and that there were not differences in the number of late potentials identified within the scar by MEM vs. PPM (73±50 vs. 76±52 late potentials per patient, p=0.965). They also found no differences in VT inducibility after procedure.

The researchers note that it remains “unknown” whether these results could be reproduced in non-ischaemic patients and/or with other ablation approaches.