Introduction:
A new automated vector-based mapping algorithm (AMA) for 3-dimensional electroanatomical mapping has recently been introduced to improve and facilitate ablation procedures for complex atrial tachyarrhythmias. AMA might have the potential to define additional ablation targets in patients with ventricular arrhythmias (VA).  The aim of this study was to present our initial experience using AMA to recognize additional catheter ablation targets in patients with VA’s.

Materials and methods:
A total number of 16 male patients with a median age of 66.1±12.4 years suffering from VA underwent catheter ablation in our hospital. The cohort consisted of six patients with history of ischemic cardiomyopathy (ICM) and ten patients with non-ischemic cardiomyopathy (NICM). Following bipolar voltage mapping under sinus rhythm or right ventricular pacing, the AMA algorithm was utilized to reveal zones of decelerated conduction velocity vectors (CVV)  based on manual thresholding enabling the dynamic view function. The threshold caliper for conduction velocity vector (Coherent® - visualization setup) was adjusted until the first slow conduction velocity vector (the bold arrows) appeared inside the electroanatomical map. Afterwards, the information from AMA was superimposed onto the endocardial reconstructions and compared to the presence of abnormal uni- and bipolar voltage suggestive for ventricular scar tissue or fibrosis. In case that slow CVV zones were located in a close relationship to areas suggestive for scarred myocardial tissue, we classified this as a match and potential ablation target (Figure 1.) 

Results:
A correlation between CVV deceleration zones from AMA and areas of abnormal low-voltage from endocardial bipolar mapping was documented in 37,5% of patients. In contrast, correlation between scar from unipolar voltage mapping and CCV deceleration zones was 94% (p=0,008). We observed no procedure related complications requiring intervention. After follow up (16±5.1 months) three patients from NICM group (30%) and two patients from ICM (33%) group had VT recurrence.

Conclusion:
The novel AMA may improve the understanding of individual VA substrates due to the visualization of decelerated CVV zones and their correlation with abnormal low voltage predominantly from unipolar mapping. The utilization of AMA in conjunction with evidence for scar tissue might result in detection of intramural or epicardial targets for VA mapping and ablation.

Figure 1. Endo- and epicardial LV reconstructions show correlation between scar tissue and deceleration zones from AMA in a patient with dilated cardiomyopathy. A – Endocardial bipolar voltage mapping (reference interval: 0.1-1.5mV) shows no evidence for an arrhythmia substrate but two deceleration areas. B – Endocardial unipolar voltage mapping (reference interval: 5-8mV) highlights a posterolateral arrhythmia substrate suggestive for epicardial scar tissue. Of note, the slow conduction areas are exactly at the border zones. C – Epicardial bipolar voltage mapping (reference interval: 0.1-1.5mV) reveals a huge scar correlating with the findings from endocardial unipolar map and AMA.