Limitations
This report was of a single operator’s practice, with analyses limited
to annotated LAPW sites of RF delivery in view of the risk of
atrio-oesophageal fistula resulting from excessive RF application at
this site. It is possible that RMA settings demonstrate greater
annotation concordance at alternative left atrial sites, however such
analyses were beyond the scope of this present report. The VISITAG™
Module filter preferences (force-over-time 100% minimum 1g, with 2mm
position stability), overdrive atrial pacing and steerable sheath use
towards achieving catheter stability and optimal ITD during continuous
RF application must be taken into account when considering these
experimental findings. If the more commonly employed force-over-time
30% minimum 4-5g CF filter was employed4,5,
intermittent catheter-tissue contact would only trigger per-site
annotation “end” if position data breached the chosen (position)
stability criteria at that time-point – i.e. the effect of RMA “on”
towards failure to identify sites of true catheter motion would be even
greater. We elected not to perform a complete re-analysis of exported
data with this different CF filter setting, since a site of stable
catheter-tissue interaction during RF by definition may only occur in
the setting of constant catheter-tissue contact (i.e. assuming no
catheter CF measurement error, force-over-time 100% ≥1g). Also, a
complete description of the effects of changing the position stability
filter setting is beyond the scope of this present report; this will be
the subject of a future manuscript.
Catheter tip motion characteristics following deliberate movement may
differ from unintentional events: due to the very high attainment of
target per-site RF delivery in this present report, a description of
position stability, CF and impedance profiles at sites of accidental
catheter motion is beyond the scope of this present report. However,
when deliberate catheter displacement events of up to
~5-7mm were not immediately identified when annotated
with RMA “on”, similar degrees of movement during unintentional
catheter displacement events are also likely to be missed.
The findings of this present report are only applicable to VISITAG™
auto-annotation guided PVI. However, EnSite Precision™ (Abbott) – the
only other system presently employing automated RF annotation, AutoMark™
– also routinely utilises respiratory motion “compensation”.
Accordingly, the findings of this present report should stimulate
investigations into the methodological rigour of “respiratory
compensation” during AutoMark™-guided AF ablation.
Finally, this report is based on analyses of just 8 PVI procedures.
However, RF annotation use provides a highly “data-rich” operative
environment for analysis, and each ~15s first-site
annotated RF application alone provided 3090 exported data points (i.e.
CF at 20Hz, impedance at 10Hz, and both position SD and position shift
at 60Hz): this present report represents a total analysis of
~165,000 mapping system-derived data points.