Antero (superopara) and mid-septal accessory pathway ablation

Antero (superopara) and mid-septal accessory pathway ablation.

NSW EP Meeting - August 2025.

1. ABLATION OF PARAHISIAN
& MID-SEPTAL ACCESSORY
PATHWAYS
Alejandro Paredes. MD, MSc, FESC.
03.09.2025

3. Supero-(para)septal
(Mid)-Septal
Infero-(para)septal

5. Nomenclature
•AnteroseptalAPsare localizedat theanterior (superior) septalsegmentof thetricuspidannuluswithin10 mm fromtheHisbundle, i.e. in thesegmentboundedbytheapexof thetricuspidannulussuperiorlyand Hisbundleinferiorly.
•Para-HisianAPsare AS APsforwhichbeforeorafterablation, a distincthigh-frequencyHisbundlepotentialwasrecorded.
•Mid-septalAPsare thosebetweenanteroseptaland posteroseptalregions.

9. Mappingof accessorypathway
•Mostof APsare thin(up to 3 mm) butrelativelylong(up to 10 mm). Don’tforgettheobliquedisposition.
•MappingtechniquesvarydependingonwhethertheAP iscapableof anterogradeand/orretrograde conduction.
•Retrograde conductingaccessorypathway
•Earliestatrial activation(theatrial insertionsite) eitherduringtachyorduringventricular stimulation.
•In cases of fastretrograde AVN conductionàVES withshort couplingintervals.
•Anterogradeconductingaccessorypathway
•Siteof earliestventricular activation(ie, precedingtheonsetof delta wave byat least0 to 10 ms in left-sideAP and 10 to 30 ms in right-sideAP.
•Unipolar signal: QS complex
•Atrial pacingfroma sitenearAP locationcan increasePE.

10. Radiofrequency
•A permanentdamageto theAV node
has beendescribedin up to 5% to 7% of thesecases.
•Low-powerRF settingàHigh
recurrence.
•Approachwilldependof experience
in eachcentre (IVC-SVC-NCC)
Cryo
•Effectiveand associatedwithno
permanentand significantdamageto thenormal AV conductionsystem.
•Cryomapping–cryoablation.
•Bestresultswithprecise mapping,
catheterstability, and aggressive
cryoablationwithfreezingat -75ºC up
to 480 s.

14. •18 ptsw/ PH-AP
•Mappingof retrograde
conductionas wellas
antegradeconduction(if
possible) in boththeright-
sidedHisbundleregionand
NCC regionwasperformed
beforeablation.
•Successfulablation: 10/10 (RS)
and 7/8 (NCC).

15. Incidenceof AV conductioninjury: 3 of 6 (50%)
at Site2, 4 of 13 (30.8%) at RMS, 7 of 34
(20.6%) at Site3, and 3 of 46 (6.5%) at Site1.ForRAS APs, successratebetweenIVC and
SVC approaches:76.6 vs. 73.3%, p = 0.63).

16. “Bump” analysis
•Cathetertrauma to AP recordedin
21 of 120 (17.5%) patientswithpara-HisianAP.
•Recurrencerateof directablationat
the”bumped” sitesare higherthan
theconventionalablationmethod
(37.5 vs 14.1%, p=0.036).
•Median recoverytime was29s
(range5-21 min) afterbumpblock.

17. •3D EAM allowedprecise catheter
visualizationwithmultiplesynchronous
and customizableviews.
•CF-enabledcathetersallowedthereal-
time visualizationof theamountand
directionof forceappliedto thetissue.
•Associatedto a reductionin numberof
RF pulses comparedto mappingand ablationwithstandard irrigatedtip
catheters.
•No complications

18. Cryo
RFA

20. Tips& Tricks
General
•EAM + tagsitesof interest(Hiscloud, mechanicalblock) + cont. recording& replay!.
•Bipolar and unipolar (QS) EGM.
•Long sheath(SR0 vs steerable)
•Ablationtarget more ontheventricular side.
•RespiratorygatingduringGA.
•Microelectrodes?, ICE?
Parahisian
•Visualizationof “His-cloud”
•RFA, ifdistanceto Hisis>10 mm.
•TitratedRF-energyapproach?
•No atrial pacingduringRFA.
•Stop ablation, if:
•Suddenimpedancerise(>10 ohms)
•PR prolongation, AV-block
•Anyjunctionalectopy
•A reverse curve technique.
•IVC –SVC -NCC
•Cryo–RF –Cryo+RF
•Ablationtarget more onthe
ventricular side.
•Sizeof a Hisisnotalwaysa
goodpredictor of AV-block à
AVN
Midseptal

21. Takehome messages
•Para-Hisianand mid-septalAPsare rarelyobservedin clinicalpractice, representing1.5% and 2% of allKent bundles, respectively.
•Ablationof RS and MS APsischallenging.
•Standard techniquesremainparamount. Don’tforgetthesignals!
•Precise and stablecathetertipmanipulationwitha steerablesheath.
•RecurrenceCryo> RFA / AcutesuccessRFA > Cryo.

22. ABLATION OF PARAHISIAN
& MID-SEPTAL ACCESSORY
PATHWAYS
Alejandro Paredes. MD, MSc, FESC.
03.09.2025