Ripple-AT Study: A multicenter and randomized study comparing 3D mapping techniques during atrial tachycardia ablations Short Title: Randomized Ripple AT Vishal Luther PhD MRCP 1 , Sharad Agarwal MD 2 , Anthony Chow PhD FRCP 3 , Michael Koa-Wing PhD MRCP 1 , Nuno Cortez-Dias PhD MD 4 , Luís Carpinteiro PhD MD 4 , João de Sousa PhD MD 4 , Richard Balasubramaniam MD 5 , David Farwell MD 6 , Shahnaz Jamil-Copley PhD MRCP 7 , Neil Srinivasan PhD MRCP 3 , Hakam Abbas BSc 3 , James Mason BSc 2 , Nikki Jones BSc 5 , George Katritsis MBChB BSc 1 , Phang Boon Lim PhD MRCP 1 , Nicholas S. Peters MD FHRS 1 , Norman Qureshi PhD MRCP 1 , Zachary Whinnett PhD MRCP 1 , Nick Linton PhD MRCP 1 , Prapa Kanagaratnam PhD FRCP 1 Institutional Affiliations: 1. Imperial College Healthcare, London, UK; 2. Papworth Hospital, Cambridge, UK. 3. Barts Heart Centre, London, UK; 4. Hospital de Santa Maria, Lisbon, Portugal; 5. Royal Bournemouth & Christchurch Hospital, Bournemouth, UK; 6. Essex Cardiothoracic Centre, Basildon, UK; 7. Nottingham University Hospital, Nottingham, UK Address for correspondence: Professor Prapa Kanagaratnam, Department of Cardiology, Mary Stanford Wing, St. Marys Hospital, Imperial College Healthcare NHS Trust, London W2 1NY, United Kingdom. Telephone: +44 (0) 203 312 3783 Email: [email protected]This abstract received the “Eric N. Prystowsky Fellows Clinical Research Award” at Heart Rhythm Society 2019. This abstract presentation also 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
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Ripple-AT Study: A multicenter and randomized study comparing 3D mapping techniques during atrial
tachycardia ablations
Short Title: Randomized Ripple AT
Vishal Luther PhD MRCP1, Sharad Agarwal MD2, Anthony Chow PhD FRCP3, Michael Koa-Wing PhD
MRCP1, Nuno Cortez-Dias PhD MD4, Luís Carpinteiro PhD MD4, João de Sousa PhD MD4, Richard
Balasubramaniam MD5, David Farwell MD6, Shahnaz Jamil-Copley PhD MRCP7, Neil Srinivasan PhD
MRCP3, Hakam Abbas BSc3, James Mason BSc2, Nikki Jones BSc5, George Katritsis MBChB BSc1,
Phang Boon Lim PhD MRCP1, Nicholas S. Peters MD FHRS1, Norman Qureshi PhD MRCP1, Zachary
of patients randomized to LAT mapping that did not meet the primary endpoint. The
cases in Figures 4 and 5 are from patients with prior surgical Atrial Septal Defect
repair, and illustrate issues related to LAT color interpolation. In Figure 4, several
early and late sites colored red and purple are seen on the final LAT display. As
these early and late sites were in close proximity, the operator applied the “early
meets late” tool to interpolate the colors between these sites and produce a uniform
pattern. When propagation was played, the operator observed continuous rotation
around scar on the anterolateral wall suggestive of small loop re-entry. However,
split potentials were identified along the circuit, implying wave-front collision, not
observed on the propagation display. Given this uncertainty, the operator crossed
over to RM. The Ripple Map demonstrated that a line of conduction block prevented
small loop re-entry. Thus, the appearance of re-entry was false, and a consequence
of over-interpolation creating the impression of re-entry.
In figure 5, the full color coded spectrum was observed within a small area
collocating with an area of low voltage consistent with the lateral surgical cannulation
site. The propagation map demonstrated wavefront turning around this site, and
sampled EGMs were fractionated, leading the operator to again consider small loop
re-entry. This site was ablated without effect. The patient crossed over to RM, where
no rotational activity was seen, rather splitting of activation on either side of this
region of probable scar. Post procedure, a band of false color interpolation spanning
the full rainbow spectrum was appreciated on the LAT map between the apparent
early and late sites on the map. This created the appearance of a slowly moving
backward wave-front and this false appearance of wavefront turning on the
propagation display. As RM does not require a WOI and does not interpolate, this
error was avoided.
Figure 6 depicts an iatrogenic AT post extensive AF ablation where the LAT WOI
had been set equally around the CS reference EGM. The subsequent activation
pattern appeared focal in origin from within the LAA. Given the absence of EGMs of
interest, this diagnosis was uncertain, and entrainment revealed this site was outside
the circuit. RM did not demonstrate focal activation from the LAA, rather activation
breakout from probable scar near the posterior floor. Post procedure, after multiple
arbitrary post hoc adjustments of the LAT WOI, it revealed a similar activation
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pattern as seen with RM. This case highlights how setting the WOI is arbitrary and
can be misleading in complex cases. As RM does not require a WOI, this limitation
can be avoided.
Despite all attempts to optimise, the LAT map in figure 7 was considered
uninterpretable, with multiple early and late sites. This was mapped from a patient
with prior mitral valvuloplasty and extensive low voltage atrial tissue. EGMs sampled
within the map were frequently long duration and multicomponent. Despite being in
close proximity, sites have been labelled as early and late due to overlapping EGMs
spanning a large portion of the set WOI. This case highlights the challenge of having
to annotate a single LAT to represent multi-component fractionated EGMs. Ripple
Mapping does not annotate, rather it presents all EGM components in its entirety.
Following crossover to RM, a breakout of activation from an extensive area of low
voltage along the posterior roof was appreciated and a decision to perform a
posterior box lesion resulted in AT termination.
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DISCUSSION
This study is the first prospective, multicenter and randomized study comparing 3D
activation mapping techniques. We show that operators experienced with LAT
mapping on the CARTO3v4 CONFIDENSE™ platform had a higher rate of AT
termination using Ripple Mapping, and achieved this with less reliance on
entrainment support.
The effectiveness of mapping tachycardia activation using LAT is proven. Published
studies document ~85% success rates in AT termination using this approach1. LAT
mapping has seen recent advances, including automated annotation to the
maximum negative unipolar EGM derivative within the period of bipolar activation,
and its incorporation with high point density. However, most of these published
studies have combined LAT with entrainment mapping such that the efficacy of LAT
mapping in isolation remains unknown. Furthermore, these studies did not report
whether ablation had been delivered at multiple incorrect sites prior to eventual AT
termination. This is the first study to measure the efficacy of LAT mapping in
isolation, without entrainment, and following the delivery of only the first ablation set.
This study demonstrated acute AT termination with first lesion set in 71% with LAT
mapping, and in only 44% without entrainment. The figures highlight three sources
for error in relation to LAT mapping that likely explain this ~30% failure rate,
including: (1) incorrect color interpolation; (2) window of interest errors and (3) mis-
annotation.
Interpolation algorithms assign the average activation time between mapped points
in order to display an interpretable propagation pattern on the assumption that
activation is uniform; however, these estimates of timing can be misleading,
especially in areas of conduction delay or block, as seen in Figure 4. “Backward
wave-fronts” are a specific interpolation error observed in macro-re-entrant circuits,
and caused the problems demonstrated in Figure 5. These occur at sites where
“early” and “late” do not quite meet, and interpolation of colors between these
apparent early and late sites occur, resulting in a slowly moving wave-front in
reverse to the true direction of activation.
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A windows of interest (WOI) is required to ensure that EGM LATs from the same
cycle are compared. However, the process of setting this window is arbitrary, with
different color coded activation patterns generated depending on the setting, as
shown in Figure 6. Whilst methods to standardise this approach around the surface
p-wave have been considered, they are only applicable in non-focal mechanisms,
which is not known at the start of the case.10 Furthermore, in diseased tissue with
prolonged conduction times, no matter how the window is set, being limited to a
single cycle can lead to very late activating sites being erroneously displayed as
early in the WOI with respect to the next cycle of activation, resulting in more than
one early site on the map.11 Ripple Mapping is the only contact-mapping system
which currently reviews more than a single tachycardia cycle length. The CARTO3v4
LAT maps used in this study present their WOI as a color bar. A WOI color wheel
has also been proposed to solve the challenges of setting a WOI. Rotation of this
wheel has the equivalent effect of sliding the WOI without causing a full map re-
compute. In principle, this can avoid some errors related to the WOI as considered
above. However, several studies have reported on a high prevalence of small
pseudo-re-entrant circuits from continuously rotating the wheel, some of which were
misdiagnosed as localized/small loop re-entry and inappropriately ablated.12, 13
Mis-annotation of LAT can lead to a complete change in the color coded pattern. The
advent of high point density acquisition with algorithms that filter out points with
inconsistent timings in relation to neighbouring LAT measurements have reduced
annotation errors. However, these errors remain prevalent, particularly in areas of
low voltage containing multicomponent EGMs as in Figure 7. Manual checking and
re-annotation of LAT when >2000points are collected is time consuming and
impractical during clinical procedures.
Whilst all 3D-mapping systems continue to develop algorithms to overcome these
limitations to LAT mapping, Ripple Mapping offers a completely alternative activation
mapping approach. RM presents activation information without the need for
annotation of activation time or setting of a window of interest, and does not
interpolate between unmapped sites.5 Patients randomized to RM in this study
achieved AT termination in 90% with the first ablation set (p=0.045).
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This superiority was partly attributable to avoiding these errors associated with LAT
mapping. It was also consequent to a unique means of studying activation in areas
of low voltage and scar. There remains no consensus on a voltage parameter to
differentiate between active and non-conducting tissue (i.e. either true scar from
fibrosis or areas of functional block dependant on the wave-front direction and atrial
rate) using endocardial mapping. LAT maps apply an arbitrary pre-set voltage
threshold to display scar, and display areas below this threshold as grey tags to
blank the color-coded map.14 With RM, displaying activation wave-fronts on a colored
voltage map enables a novel approach to defining this voltage parameter that
differentiates electrically active myocardium from non-conducting tissue (voltage
thresholding).8 The example in Figure 3 is a case where only the common isthmus of
the dual-loop tachycardia needed to be ablated. This was possible because of the
simultaneous display of activating and non-conducting myocardium during
tachycardia that helped determine the optimal site for ablation. This can be
particularly helpful in peri-mitral tachycardias in which conventional mitral isthmus
lines can be avoided.
Entrainment enhances our electrophysiological understanding of the AT circuit prior
to ablation, and this study does not advocate entrainment avoidance.15 However,
entrainment does have limitations in areas of low voltage due to pacing latency, non-
capture, and can cause degeneration to AF.16 In this study, patients randomized to
RM underwent significantly less entrainment than those in the LAT group (p=0.01),
as operators felt more confident to ablate the AT based on the Ripple Map alone.
Entrainment appears to be essential to LAT mapping to help overcome the core
limitations of this approach, whilst with RM it was more supportive by confirming a
diagnosis.
RM looks very different to conventional LAT activation maps. There is a learning
curve, and each operator (who had extensive experience in LAT mapping and
entrainment) received 2-3hrs of formal training in RM on a workstation with example
cases. This was followed by 4 consecutive clinical cases where operators made a
diagnosis with RM first, with the improved diagnostic efficacy of RM already apparent
at that stage.9 These operators did not need technical support from industry
representatives to make these diagnoses. We would consider similar training to be
essential for other operators aiming to replicate the results seen in this study.
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Whilst this study was specific to mapping EGMs within the atria, RM is also suited to
mapping EGMs within the ventricle. We and others have shown how RM can be
used to follow late potentials through channels of slow conduction that might support
re-entry.17, 18 Ripple Mapping to study VT and substrate during sinus rhythm has a
very different workflow due to the main challenge being differentiating local and far-
field EGMs.
Limitations:The objective of this study was to assess the diagnostic efficacy of each mapping
technique in the acute setting, and does not consider the best approach to achieve
long-term freedom from AT. The analysis of long-term outcomes of patients
randomised to each mapping arm would require a different protocol that prohibited
crossover to the other mapping arm during the entire case, and mandated post-
ablation inducibility testing (which was performed at operator discretion in this
protocol) and treatment of any subsequent ATs using the same mapping approach.
These cases were all performed on the CARTO3v4 CONFIDENSE™ platform, and
some of the findings might not apply to other mapping software.
Approximately 20% of patients recruited were not included in the study analysis due
to tachycardia termination before mapping was started/completed. We excluded
these patients as the ATs were not stable and therefore our endpoint of acute
termination during ablation would not have been robust. The best approach to
achieve acute success and long-term benefit in this group of patients needs further
study.
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CONCLUSION
This prospective, randomized and multi-center study demonstrates that Ripple
Mapping is superior to LAT mapping on the CARTO3v4 CONFIDENSE™ platform in
achieving acute atrial tachycardia termination using the first delivered ablation set,
with reduced reliance on entrainment to assist diagnosis.
Sources of Funding: The study was funded by a clinical study grant from Biosense Webster
and a British Heart Foundation Clinical Research Training Fellowship award (no. FS/15/12/31239).
Disclosures: Imperial Innovations holds Intellectual Property relating to Ripple Mapping on behalf
of PK and NL, who have also received royalties from Biosense Webster. PK, NL, SJC and VL have
received consulting fees with respect to Ripple Mapping from Biosense Webster. The remaining
authors have nothing to disclose.
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REFERENCES
1. Chae, S.; Oral, H.; Good, E.; Dey, S.; Wimmer, A.; Crawford, T.; Wells, D.; Sarrazin, J. F.; Chalfoun, N.; Kuhne, M.; Fortino, J.; Huether, E.; Lemerand, T.; Pelosi, F.; Bogun, F.; Morady, F.; Chugh, A., Atrial tachycardia after circumferential pulmonary vein ablation of atrial fibrillation: mechanistic insights, results of catheter ablation, and risk factors for recurrence. J Am Coll Cardiol 2007, 50, 1781-7.2. Zhang, X. D.; Gu, J.; Jiang, W. F.; Zhao, L.; Zhou, L.; Wang, Y. L.; Liu, Y. G.; Liu, X., Optimal rhythm-control strategy for recurrent atrial tachycardia after catheter ablation of persistent atrial fibrillation: a randomized clinical trial. Eur Heart J 2014, 35, 1327-34.3. Jais, P.; Shah, D. C.; Haissaguerre, M.; Hocini, M.; Peng, J. T.; Takahashi, A.; Garrigue, S.; Le Metayer, P.; Clementy, J., Mapping and ablation of left atrial flutters. Circulation 2000, 101, 2928-34.4. Del Carpio Munoz, F.; Buescher, T. L.; Asirvatham, S. J., Teaching points with 3-dimensional mapping of cardiac arrhythmias: teaching point 3: when early is not early. Circ Arrhythm Electrophysiol 2011, 4, e11-4.5. Linton, N. W.; Koa-Wing, M.; Francis, D. P.; Kojodjojo, P.; Lim, P. B.; Salukhe, T. V.; Whinnett, Z.; Davies, D. W.; Peters, N. S.; O'Neill, M. D.; Kanagaratnam, P., Cardiac ripple mapping: a novel three-dimensional visualization method for use with electroanatomic mapping of cardiac arrhythmias. Heart Rhythm 2009, 6, 1754-62.6. Jamil-Copley, S.; Linton, N.; Koa-Wing, M.; Kojodjojo, P.; Lim, P. B.; Malcolme-Lawes, L.; Whinnett, Z.; Wright, I.; Davies, W.; Peters, N.; Francis, D. P.; Kanagaratnam, P., Application of ripple mapping with an electroanatomic mapping system for diagnosis of atrial tachycardias. J Cardiovasc Electrophysiol 2013, 24, 1361-9.7. Koa-Wing, M.; Nakagawa, H.; Luther, V.; Jamil-Copley, S.; Linton, N.; Sandler, B.; Qureshi, N.; Peters, N. S.; Davies, D. W.; Francis, D. P.; Jackman, W.; Kanagaratnam, P., A diagnostic algorithm to optimize data collection and interpretation of Ripple Maps in atrial tachycardias. Int J Cardiol 2015, 199, 391-400.8. Luther, V.; Linton, N. W.; Koa-Wing, M.; Lim, P. B.; Jamil-Copley, S.; Qureshi, N.; Ng, F. S.; Hayat, S.; Whinnett, Z.; Davies, D. W.; Peters, N. S.; Kanagaratnam, P., A Prospective Study of Ripple Mapping in Atrial Tachycardias: A Novel Approach to Interpreting Activation in Low-Voltage Areas. Circ Arrhythm Electrophysiol 2016, 9, e003582.9. Luther, V.; Cortez-Dias, N.; Carpinteiro, L.; de Sousa, J.; Balasubramaniam, R.; Agarwal, S.; Farwell, D.; Sopher, M.; Babu, G.; Till, R.; Jones, N.; Tan, S.; Chow, A.; Lowe, M.; Lane, J.; Pappachan, N.; Linton, N.; Kanagaratnam, P., Ripple mapping: Initial multicenter experience of an intuitive approach to overcoming the limitations of 3D activation mapping. J Cardiovasc Electrophysiol 2017, 28, 1285-1294.10. De Ponti, R.; Verlato, R.; Bertaglia, E.; Del Greco, M.; Fusco, A.; Bottoni, N.; Drago, F.; Sciarra, L.; Ometto, R.; Mantovan, R.; Salerno-Uriarte, J. A., Treatment of macro-re-entrant atrial tachycardia based on electroanatomic mapping: identification and ablation of the mid-diastolic isthmus. Europace 2007, 9, 449-57.11. Ju, W.; Yang, B.; Chen, H.; Zhang, F.; Gu, K.; Yu, J.; Li, M.; Yang, G.; Cao, K.; Chen, M., Mapping of focal atrial tachycardia with an uninterpretable activation map after extensive atrial ablation: tricks and tips. Circ Arrhythm Electrophysiol 2014, 7, 598-604.12. Luther, V.; Sikkel, M.; Bennett, N.; Guerrero, F.; Leong, K.; Qureshi, N.; Ng, F. S.; Hayat, S. A.; Sohaib, S. M.; Malcolme-Lawes, L.; Lim, E.; Wright, I.; Koa-Wing, M.; Lefroy, D. C.; Linton, N. W.; Whinnett, Z.; Kanagaratnam, P.; Davies, D. W.; Peters, N. S.; Lim, P. B., Visualizing Localized Reentry With Ultra-High Density Mapping in Iatrogenic Atrial Tachycardia: Beware Pseudo-Reentry. Circ Arrhythm Electrophysiol 2017, 10.
13. Bradfield, J. S.; Huang, W.; Tung, R.; Buch, E.; Okhovat, J. P.; Fujimura, O.; Boyle, N. G.; Gornbein, J.; Ellenbogen, K. A.; Shivkumar, K., Tissue voltage discordance during tachycardia versus sinus rhythm: implications for catheter ablation. Heart Rhythm 2013, 10, 800-4.14. Kalman, J. M.; VanHare, G. F.; Olgin, J. E.; Saxon, L. A.; Stark, S. I.; Lesh, M. D., Ablation of 'incisional' reentrant atrial tachycardia complicating surgery for congenital heart disease. Use of entrainment to define a critical isthmus of conduction. Circulation 1996, 93, 502-12.15. Pathik, B.; Lee, G.; Nalliah, C.; Joseph, S.; Morton, J. B.; Sparks, P. B.; Sanders, P.; Kistler, P. M.; Kalman, J. M., Entrainment and high-density three-dimensional mapping in right atrial macroreentry provide critical complementary information: Entrainment may unmask "visual reentry" as passive. Heart Rhythm 2017, 14, 1541-1549.16. Vollmann, D.; Stevenson, W. G.; Luthje, L.; Sohns, C.; John, R. M.; Zabel, M.; Michaud, G. F., Misleading long post-pacing interval after entrainment of typical atrial flutter from the cavotricuspid isthmus. J Am Coll Cardiol 2012, 59, 819-24.17. Luther, V.; Linton, N. W.; Jamil-Copley, S.; Koa-Wing, M.; Lim, P. B.; Qureshi, N.; Ng, F. S.; Hayat, S.; Whinnett, Z.; Davies, D. W.; Peters, N. S.; Kanagaratnam, P., A Prospective Study of Ripple Mapping the Post-Infarct Ventricular Scar to Guide Substrate Ablation for Ventricular Tachycardia. Circ Arrhythm Electrophysiol 2016, 9.18. Xie, S.; Kubala, M.; Liang, J. J.; Yang, J.; Desjardins, B.; Santangeli, P.; van der Geest, R. J.; Schaller, R.; Riley, M.; Supple, G.; Frankel, D. S.; Callans, D.; Pac, E. Z.; Marchlinski, F.; Nazarian, S., Utility of ripple mapping for identification of slow conduction channels during ventricular tachycardia ablation in the setting of arrhythmogenic right ventricular cardiomyopathy. J Cardiovasc Electrophysiol 2019, 30, 366-373.
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Ripple Mapping of an Atrial Tachycardia – Diagnostic Steps
Mapping • Multipolar mapping - Lasso/PentaRay
• Colour threshold 5mm: point density = no grey areas (usually >2000points).
• Only “points projected” displayed (visualisation set-up)
• Annular points tagged and mitral/tricuspid annulus removed
Surface Voltage thresholding • Bipolar voltage map displayed - set empirically at to 0.3mV – 0.3mV on custom settings
• Play Ripple Map and reduce voltage limits in 0.05mV steps (i.e. 0.25mV – 0.25mV; continued down to 0.05mV – 0.05mV as required) until no ripple wave-fronts in red areas (non-activating tissue)
• Ripple bar wave-fronts should only visible in purple areas
Identifying mechanism • Study ripple activation in small patches of geometry. Use design lines with arrowheads to mark these wave-fronts throughout the entire chamber
• Follow the arrows backwards to identify focal source or re-entrant circuit.
• Reduce “Show bars above” to 0.03mV - study activation in areas of interest, to locate 1) earliest bar of focal source or 2) narrowest isthmus of re-entrant circuit.
Table 1: Protocol for Atrial Tachycardia diagnosis using Ripple Mapping
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Table 2: Baseline demographics and mapping details
RM - Ripple Mapping; LAT – Local Activation Time; RA – right atrium; LA – left atrium; PVI – pulmonary vein isolation; CFAE – complex fractionated atrial electrogram; AT – atrial tachycardia; denotes 3 missing values; denotes 4 missing values.
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Baseline CharacteristicsAssigned Group
p valueRM LAT
No of Patients 42 41
Prior atrial ablation or cardiac surgery (%) 83 85 1.00
Age (yrs) 65±9 65±10 0.78
Prior atrial ablation (%)(RA or LA) 76 80 0.80
Prior PVI (%) 71 71 NA
Prior LA substrate ablation (e.g. lines/CFAE) (%) 48 29 0.12
Prior RA ablation only (%) 5 10 0.43
Prior cardiac surgery without ablation (%) 7 5 1.00
AT cycle length/ ms, median 267* 260* 0.2
Pentaray use (%) 64 63 0.93
Collected Points, median 2681* 2219 0.44
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Figure Legends:
Figure 1: Study design and patient numbers
Figure 2: Results of acute ablation outcomes.
Figure 3: Randomized to Ripple Mapping. Voltage thresholding defines the critical
isthmus (See also supplementary video 1).
Patient with an idiopathic left AT (262ms). (A). Upper panel - bipolar voltage map set
to 0.30mV– 0.30mV. Tissue with voltage <0.30mV is displayed in red, and >0.30mV
in purple. A large area colored red was seen on the anterior wall. Wave-fronts of
ripple bars (yellow circle) were seen in areas of the voltage map colored red. (B) The
surface voltage limits were reduced until 0.15mV-0.15mV (i.e. red=<0.15mV;
purple=>0.15mV) – here no Ripple bars were seen in areas colored red. At this
voltage setting, an island of red tissue was seen on the anterior wall with ripple bars
circumnavigating clockwise around it (marked out by white arrows). Middle panel –
Ripple markings were sampled around this island, and their corresponding EGMs
spanned the ATCL (3 consecutive EGM cycles shown). Shown in the accompanying
video is a second circuit travelling counter-clockwise around the mitral annulus. Both
circuits were dependent on a narrow isthmus between the inferior border of this
island and the mitral annulus. Lower panel - transecting this critical isthmus with
ablation terminated tachycardia.
Figure 4: Randomized to LAT mapping. Interpolation creates the false impression of
small loop re-entry (See also supplementary video 2).
Patient with a prior surgical ASD repair mapped in AT (260ms) in the right atrium. A)
LAT map (modified AP) with the WOI set either side of the reference signal (-130ms
to +130ms). More than one region of early and late were seen (labelled). B) The
“early meets late” tool was applied (80%-default) and color interpolation between
these early and late sites were filled (dark red). Scar was highlighted as areas with
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peak bipolar voltage amplitude ≤0.03mV and colored grey. All the colors of the LAT
spectrum were seen to progress around a patch of scar on the anterolateral wall
suggestive of small loop re-entry. However, split potentials were identified along the
circuit, implying wave-front collision in the circuit. C) The Ripple Map demonstrated
that a line of conduction block prevented small loop re-entry around this patch of
scar, as evident by a line of double potentials along it (double yellow lines). In fact,
ripple bars rotated around this line of block, creating a “larger loop” re-entry. The
pattern of activation is depicted by white design lines, and can be viewed in the
corresponding video. Entrainment supported this observation – the post pacing
interval was long within the interpolated false small loop circuit seen by the LAT map,
and shortened moving superiorly into larger loop circuit seen with the Ripple Map.
Figure 5: Randomized to LAT mapping. Interpolation creates a false backward
wavefront (See also supplementary video 3).
Another patient with prior surgical ASD repair was mapped in AT (270ms) in the right
atrium. A) The operator observed the full rainbow color spectrum around the lateral
RA corresponding to B) an area of low voltage <0.30mV on the bipolar voltage map
and considered this small loop re-entry based on C) the presence of long and
fractionated EGMs within the circuit and the appearance of wavefront
turning/curvature (although not a complete rotation) on the corresponding LAT
propagation map (see video). However, ablation at this site (red circular VisiTag
disks) was ineffective. D) There was no evidence of wavefront curvature on the
Ripple Map, rather splitting of wavefronts on either side of this region of scar. E) A
band of false color interpolation spanning the full rainbow color spectrum was
evident between the early and late sites on the LAT map (labelled) that created the
appearance of a slowly moving back ward wave-front and the impression of wave-
front turning.
Figure 6: Randomized to LAT mapping. Varying LAT activation patterns when
changing the window of interest (See also supplementary video 4).
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Patient with post AF ablation (PVI, Roof + Mitral isthmus lines, CFAE ablation) AT
(258ms). Upper panel: The WOI was set either side of the reference signal to span
90% of the TCL. The LAT map, seen in AP (A) and PA (B) depicts earliest focal
activation (red) within the left atrial appendage. C) The corresponding voltage map
(PA) demonstrates extensive substrate <0.1mV (colored red). Unlike the LAT map,
RM revealed a breakout of activation from probable scar near the posterior floor
(yellow star), considered the exit of a region of slow conduction supporting a macro-
re-entrant circuit around the mitral annulus (white design lines). D) Adjustment of the
LAT WOI to (-18ms) to (+201ms) revealed the same breakout activation pattern (red
isochrone collocating with yellow star) as suggested by RM, but considered the
mechanism focal rather than part of a macro-re-entrant circuit. AT terminated in the