1) Plasma mediated ablation (PMA) uses plasma created by applying energy to electrodes to break down intramolecular bonds in soft tissue without high temperatures.
2) PMA shows potential for recanalizing chronic total occlusions (CTOs) in an antegrade approach using streamers to penetrate distal caps.
3) A representative case demonstrated successful penetration of a distal CTO cap using an antegrade PMA approach with dual wires to create streamers and ablate tissue.
2. Plasma mediated ablation system
What is plasma…
When given energy, electrons will enter “excitation“ state, in which their
gyration radius became larger and easier to leave atoms. They will eventually
pop out from the bonding , “ionization”. These protruding electrons, so called
"free electrons“, left behind the particles as "ions". This state, in which
electrons and ions became flutter (nuclei and electrons are not properly
coupled and stabilized), are called “Plasma".
A state in which free electrons and ions are moving
freely (nuclei and electron are not coupled, unstable)
Under this environment, plasma can be simultaneously
created by vigorously moving the electrons.
5. Plasma mediated ablation (PMA）
K. Katsanos, “Overview of Thermal Ablation: Plasma-Mediated Ablation“ Springer, 2012
Excitation of electrolytes in conductive medium
(such as saline solution) using bipolar RF energy
Precisely focused plasma ion field created.
Plasma breaks down intramolecular bonds by
cavitating or dissolving soft tissue at relatively
low temperature
*Also referred to as radiofrequency ionization, plasma-radiofrequency or plasma-RF ablation,
controlled ablation or cold ablation.
6. Mechanism of retrograde PMA
dense calcium
channel
in calcium
Formation of plasma between two electrodes (distal of guide wires).
Channel between two electrodes electrically created.
7. Mechanism of retrograde PMA
Streamer
• Randomly occurred
between electrodes
• Low reactivity
• Low temperature
• Create channel to
connect electrodes
• High reactivity
• High temperature
Arc
• Create channel to
connect electrodes
• High reactivity
• Low temperature
Spark
SparkStreamerVoltage(V)
Current(A)
Time (s)
Plasma created on PMA
8. 9
Characteristics of plasma discharges
Under atmospheric pressure
streamer
Dielectric
breakdown
A. Descoeudres, “Characterization of electrical discharge machining plasmas”, Ph.D. thesis, 2006
Corona discharge
Dielectric breakdown
Spark
Arc discharge
Dark region
Streamer
9. Channel creation using streamer-spark model
10
Mechanism:
Step1： Vapor layer formation
• Liquid near electrode vaporized from Joule
heating.
Step2：Plasma region formation
• Plasma formed inside vapor layer.
• Vapor layer fulfilled with plasma.
Step3：Vapor layer expansion
• New vapor layer formed again by Joule
heating, shock wave, etching at boundary
layer. (Exact mechanism is yet to be known.)
Step4：Plasma region expansion
• Plasma region expands along with expanded
vapor layer.
Vapor layer
New vapor layer
Plasma region
AC Power
AC Power
AC Power
AC Power
10. 11
Obsevation:
Step1： Vapor layer formation
• Liquid near electrode vaporized from
Joule heating.
Step2：Plasma region formation
• Plasma formed inside vapor layer.
• Vapor layer fulfilled with plasma.
Step3：Vapor layer expansion
• New vapor layer formed again by Joule
heating, shock wave, etching at boundary
layer. (Exact mechanism is yet to be
known.)
Step4：Plasma region expansion
• Plasma region expands along with
expanded vapor layer.
Channel creation using streamer-spark model
Streamer
Spark
Repetition of
streamers
Vapor layer expansion
Spark occurrence
11. 12
Obsevation:
Step1： Vapor layer formation
• Liquid near electrode vaporized from
Joule heating.
Step2：Plasma region formation
• Plasma formed inside vapor layer.
• Vapor layer fulfilled with plasma.
Step3：Vapor layer expansion
• New vapor layer formed again by Joule
heating, shock wave, etching at boundary
layer. (Exact mechanism is yet to be
known.)
Step4：Plasma region expansion
• Plasma region expands along with
expanded vapor layer.
Channel creation using streamer-spark model
Streamer
Spark
Repetition of
streamers
Vapor layer expansion
Spark occurrence
14. FIM 1
FIM
number
site date CASE Patient ID age sex
Targeted CTO
(intended
ablation site)
Intended use of
PlasmaWire
FIM-1 SCVC Oct. 21 KN 70412581 69 M
mid-RCA
(distal)
Ant + Retro
FIM-2 SCVC Oct. 21 FK 70424407 56 M
mid-RCA
(distal bifur.)
Ant + Ant
FIM-3 SCVC Oct. 22 YS 70459383 68 M
prox-LAD
(prox)
Ant + Ant
FIM-4 SCVC Oct. 22 KB 70453348 69 M
prox-RCA
(prox)
Ant + Retro
FIM-5 NHC Oct. 27 HS 00332239 64 M
mid-RCA
(mid)
Ant + Retro
FIM-6 THC Oct. 28 KY 691291 51 M
distal-RCA
(distal)
Ant + Retro
FIM-7 SCVC Dec. 2 TH 70471802 89 M
mid-RCA
(mid)
Ant + Retro
15. How can PMA recanalize distal cap in antegrade?
21. FIM of PlasmaWire
FIM-3 (planning)
target vessel contralateral
Guiding (planned) Hyperion SPB 3.75 with side hole 8Fr Hyperion JR no side hole 6 Fr
Access route Rt femoral Lt femoral
Planned fashion of Plasma wire
use
Antegrade + Antegrade
Retrograde route not planned (distal PD septal br for backup)
CTO wires for preparation Step-up from Gaia not planned
Procedure for preparation 1. Calcium pipe is negotiated by Gaia.
2. PlasmaWires exchange are done inside calcium pipe.
3. Super-selective injection in conus branch is mandatory.
4. The ablation site is CTO exit at the end of calcium.
PlasmaWires
22. FIM of PlasmaWire
FIM-3 (results)
Pre-PCI (simultaneous injection using super-selective injection through the conus br)
AP cranial LAO cranial
23. FIM of PlasmaWire
FIM-3 (results)
After the false channel was created, plasma ablation was attempted in the false lumen beside the proximal end of distal true lumen.
The large false lumen was created below the
distal true lumen by Gaia 2nd.
Ablation site (antegrade+antegrade)
24. FIM of PlasmaWire
FIM-3 (results)
After the false channel was created, plasma ablation was attempted in the false lumen beside the proximal end of distal true lumen.
During ablation
(antegrade+antegrade)
Position for ablation
(Both PlasmaWires are positioned in false lumen
so that the distal true lumen is being collapsed. )
(gap: 1.40 mm).
Total ablation duration: 1.8 sec
Total energy delivered: 1.06 J
25. FIM of PlasmaWire
FIM-3 (results)
Collateral injection immediately after activation showed the restored true lumen and shift of PlasmaWires from the false lumen to
the true lumen.
Shift of both PlasmaWires to true lumen
(re-entry)Immediately restored distal true lumen
Immediately after activation Immediately after activationJust before activation
(collapsed distal true lumen)
A SecondPatient with Electrical Re-entry
26. FIM of PlasmaWire
FIM-3 (results)
After connecting channel was visualized by tip injection, the channel was recrossed with a very floppy wire (SUOH03). Then IVUS
was done to check the channel.
Immediately restored distal true lumen
Successful crossing with a Plasma2 wire
However, the Plasma2 wire was spontaneously pulled out due to its
excessive lubriciousness. Then, tip injection was done to visualize
the created channel.
ablation point
IVUS was pulled back
from here
27. FIM of PlasmaWire
FIM-3 (results)
Immediately restored distal true lumen
Successful crossing with a Plasma2 wire
Pullback IVUS image
IVUS findings of connecting channel created by plasma ablation
Distal to connecting channel (in the
true lumen)
big subintimal lumen created by Gaia
2nd prior to ablation
distal true lumen
Connecting channel between false lumen and
true lumen
Distal end of calcium pipe
29. PMA: Antegrade V.S. Retrograde
“Spark” is considered to be effective for ablation on Retrograde approach.
But May be not on Antegrade approach.
?
So…
Can PMA really be useful for Antegrade?
Possible, by using “Streamer”.
(Similar to PEAK)
Electron avalanche
S. Xie et. al, J. Physics of Plasmas, 22 (2015)
30. Penetration on tissue by streamer
“Ablation with Streamer”
Mechanism:
D. Palanker, “Method and apparatus for pulsed plasma-mediated electrosurgery in liquid media.“ U.S. Patent No. 6,135,998. 24 Oct. 2000.
A. Vankov, D. Palanker. "Nanosecond plasma-mediated electrosurgery with elongated electrodes."
Journal of applied physics 101.12 (2007): 124701.
InsulatorElectrode InsulatorElectrode
De-ionized water Saline
streamer streamerstreamer
Electrode Insulator
Shock wave
PMA is possible by “Streamer” created from high electric field.
31. Penetration on tissue by streamer
Comparison with bench study:
Reference Bench Test
March 2, 2017 (0.05 Mfps)
April 14, 2017 (1 Mfps)
D. Palanker, “Method and apparatus for
pulsed plasma-mediated electrosurgery
in liquid media.“
U.S. Patent No. 6,135,998. 24 Oct. 2000.
Similar phenomena
Streamer: Shock wave:
Reference
I.P.Hoffer, “Shock waves generated
by corona-like discharges in water”,
Ph.D. thesis, 2014
April 14, 2017 (2 Mfps)
Bench Test
Shock wave
Shock wave
32. Penetration on tissue by streamer
Electric field simulation: DC mode, 2-electrodes model (Double wires)
1200V 0V0V 1200V
E field
Easier to form
plasma.
33. Penetration on tissue by streamer
Electric field simulation: DC mode, 2-electrodes model (Double wires)
When in contact with dielectric layer,
Plasma is easier to propagate onto
front direction.
Dielectric layer
Dielectric layer
Electric field is focused on
smaller area. Higher density
34. Penetration on tissue by streamer
Electric field simulation: DC mode, 2-electrodes model (Double wires)
When in contact with dielectric layer,
Plasma is easier to propagate onto
front direction.
Dielectric layer
Dielectric layer
Electric field is focused on
smaller area. Higher density
Direct wire
Indirect wire
36. Penetration on tissue by streamer
◆Total Pulse: 90 Pulses
0Pulses /90Pulses 33Pulses /90Pulses 64Pulses /90Pulses
Cow`s Aortic wall
Streamer occurred. Successfully penetrated
Direct wire
Indirect wire
37. Procedure of antegrade PMA by streamer
Sigle guide-wiring in CTO Lesion
Small balloon dilatation (if needed)
Advancement of guidewire at distal cap
WOTW catheter delivery
PMA to penetrate distal cap
38. Procedure of antegrade PMA by streamer
Sigle guide-wiring in CTO Lesion
Small balloon dilatation (if needed)
Advancement of guidewire at distal cap
WOTW catheter delivery
PMA to penetrate distal cap
45. A representative case in FIM2
target vessel Contralateral
Guiding (planned) Hyperion AL 1 with side hole 8Fr Diagnostic catheter JL3.5 6Fr
Access route Rt femoral
Planned fashion of PMA wire use Antegrade
CTO wires for preparation GAIA 2nd
Planned procedure for PMA 1. GAIA 2nd and Corsair are advanced to CTO body.
2. Corsair is exchanged to WOTW for introduce “direct” and “indirect” wires.
3. Manipulation of “direct wire”.
4. PMA is performed in CTO body if needed.
5. PMA is performed to penetrate distal cap.
55. Summary of antegrade PMA
PMA may be considered as 1st strategy in antegrade approach.
Guide wire with PMA can be advanced to the appropriate direction even
in the hard tissue.
PMA may simplify the penetration procedure at distal cap of the CTO.
Tissue ablation is occurred around the tip of not only “direct wire” but
also “indirect wire”. Therefore, the direction of both wires in CTO
segment is important to prevent complication.
