The LUMIPOINT™ software: are we just at the turning point?

The substrate analysis of both atrial and ventricular arrhythmias is a continuous challenge for the eletrophysiologists and the technology manufacturers.

The ability to detect very low-amplitude electrograms (EGMs), to discriminate near-field from the far-field signals, and the capability to record and annotate a high number of EGMs simultaneously by means of multipolar catheters are critical to the accurate definition of arrhythmia substrate;¹ above all, this has to be feasible on-line to help the ablation design and potentially impact the procedure outcome.

Nevertheless, its widely accepted that the simple recording of bipolar voltage amplitude is poorly specific to the evaluation of the arrhythmia substrate; the EGM characterization is nowadays focused on the signal complexity and timing, with the aim of describing the arrhythmia mechanism during tachycardia and the surrogate markers during sinus rhythm.

The LUMIPOINT™ software has been recently implemented to meet these specific demands. The analysis of a given map can be activated when the tool is switched on, and different features can be selected to provide a comprehensive overview of the mapping findings.

A first glimpse into the arrhythmia mechanism is provided by the SKYLINE™ tool. This helps to define whether a re-entrant or a focal mechanism is responsible for the tachycardia, showing a histogram of areas being activated at any given timeframe. A dome-shaped morphology would favour the focal mechanism, as long as homogenous high-density map is recorded.

A current challenge of activation maps is the proper annotation of near-field, low-amplitude EGMs since they are frequently hampered by higher-voltage far-field signals. Features of the LUMIPOINT™ tool show the activated areas irrespective of the system annotation, so the activation map could be easily optimized with different windows of interest, to scan diastolic activity during re-entrant tachycardias or late activation during sinus rhythm. Once the proper timeframe has been selected by the operator, the Group Reannotation tool automatically resets the annotation of the selected EGMs.

In the contemporary era of very complex arrhythmias treated by catheter ablation, like post-incisional tachycardias, re-entry involving both atria- or endo-epicardial isthmus extension and multiple propagating wavefronts, even a timing-based analysis still appears to miss important clues of the substrate mapping.

Long-duration EGMs recorded in scar areas are highly fragmented, frequently challenging a meaningful timing annotation. Indeed, continuous fragmented EGMs can have the same local timing of discrete late potentials, but they represent areas of slowdown conduction,² being late potentials the possible downstream effect of the conduction delay. Remote studies and recent experiences³ showed that fragmented EGMs are critical to the re-entry mechanism to occur; their characterization is then a primary goal of substrate mapping.

The complexity tool allows the system to highlight specific subset of EGMs (continuous, split potentials, and fragmented) and show their distribution on the map, according to the operator’s choice. This is not just a tool for the frequency domain analysis, but an index corrected for the baseline noise. Areas of conduction blocks can be also characterized on the sinus rhythm maps, to assess the residual conduction properties inside the low-voltage areas or the effect of previous ablation attempts.

This could be beneficial in multiple settings of complex arrhythmia analysis, and also in pulmonary veins isolation, with the prompt identification of the conduction gaps, or in the assessment of linear ablation efficacy, tracking the lines of double potentials. The consistency of the highlighted areas can be also proven, since a Trend tool is able to show pooled areas with the same EGMs configuration.

In our view, a step forward to the current mapping techniques would be to add a ‘further dimension’ in the electroanatomical mapping, to overcome the current ‘static’ interpretation of activation maps. Overall, the LUMIPOINT™ software features would contribute to this new mindset.

The propagation analysis during tachycardia would help to identify the effective critical isthmus vs. dead-end pathways (exhausting wavefronts), especially in post-surgical arrhythmias or complex scar architectures supporting unusual isthmus configurations. In these settings, indeed, multiple areas of diastolic activation often coexist, and the identification of the critical isthmus relies on the analysis of relationship in the relative timing of a given subset of EGMs as compared to nearby areas; the sequential spotlight on different timeframe and EGMs morphologies of the LUMIPOINT™ software has been developed to accomplish the task.

In the setting of ventricular tachycardia (VT) substrate mapping, the propagation analysis is expected to fill some of the current evidence gaps. Compelling data are needed to link the conduction properties during sinus rhythm to the re-entry circuits, since the markers that have been described over the last years, mainly LAVAs and LPs,^4,5 are not always mechanistically related to a given VT. Areas of slow conduction in sinus rhythm, instead, appear to be critically related to the isthmus location; the characterization of these areas would define new ablation targets and potentially improve the treatment of unmappable VTs. During a re-entrant tachycardia, areas with the maximum slowdown are frequently at the isthmus entrance, which represent an ideal target for the ablation, but the efficacy of this strategy has not been systematically assessed.

High-density mapping is essential for the treatment of post-incisional atrial arrhythmias, whenever multiple previous ablations or scarring process represent the milieu for very complex circuits. The LUMIPOINT™ tool, again, would allow a thorough characterization of propagation and local EGMs, with the extra value of recording very low-amplitude potentials which are frequently scattered in post-surgical atria.

In conclusion, the systematic implementation of LUMIPOINT™ in the field of electroanatomical mapping will provide an automatic tool that simplifies analysis of complex EGMs. When it comes to the reannotation of high-density maps with a huge amount of acquired signals (i.e. 20.000 points), the process is time-consuming and affected by post-operative factors. The introduction of a standard tool that prompt identification of EGMs with preset features is a step towards the availability of on-line, less-subjective interpretation of complex EGMs.

Funding

This paper was published as part of a supplement supported by a grant by Boston Scientific Italy.

Conflict of interest: C.B.: Consultant Fee (Abbott; Boston Scientific). All other authors declared no conflict of interest.

The opinions expressed in this article are not necessarily those of the Editors of Europace or of the European Society of Cardiology.

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