A Second Cryoballoon System- new and improved?
Wilber W. Su MD1,2
Banner-University Medical Center, Phoenix, AZ
Stanford University Medical Center, Palo Alto, CA
Disclosures: Dr Su has received consulting fees, honoraria, and
research grants from Medtronic and Boston Scientific.
Funding: None
Cryoballoon as a single-shot pulmonary vein (PV) isolation tool with the
Arctic FrontTM Cryoablation System has been
popularized world-wide, with over 700,000 cases performed to date and
vast clinical experience and expanded indications.1Technique, dosing, and best practices to avoid complications has also
improved with the Arctic Front Advance cryoballoon over the past 15
years.2,3 A second cryoballoon is now in clinical use
with initial approval in EU and ongoing IDE trial in the U.S. The design
similarities between the Medtronic Arctic Front
AdvanceTM versus the Boston Scientific
PolaRxTM are noticeable—similar delivery mechanism,
sheath size, cryoballoon shape, size, and refrigerant. Is the new Boston
Scientific system comparable or improved compared to that of the
existing Medtronic system?
Crete et al reports their first experience of the two cryoballoon
systems. Scope of the manuscript describes the procedural and clinical
outcome of AF ablation in a small cohort of 40 patients, but it does
offer the initial glimpse into the broad differences or lack thereof
between the two systems. While the initial experience and reported
outcome is generally good, with an acute procedural success and
complication rate. Importantly, either system was able to produce a near
100% acute PV isolation with a mean procedure time of 60 minutes.
Complications rate are minimal, and all are testament to the technology
that has become reproducible in different operator’s hands for a short,
successful, PV isolation with low risk.
Importantly, significant differences in the biophysical parameters
(i.e. rate of cooling, cryoballoon nadir temperatures, thaw
times) during cryoablation with the two technologies were reported.
Biophysical characteristics during ablation with the Arctic Front
Advance cryoballoon have been carefully evaluated via pre-clinical
studies, computational modeling, and randomized controlled trials over
the last 15 years and have been used to define dosing algorithms and
best practices.2-5 Despite the similarities between
the two cryoballoons, results from this study suggest the PolaRx balloon
has unique biophysical parameters and may need ongoing investigation to
optimize dosing.
Significant differences do exist
between the two system that is not discussed in detail, most noteworthy
is the cryoballoon ablation pressure: the Medtronic cryoballoon
inflation pressure is low(approximately 3 psi. After the initiation of
the ablation, pressure increases up to six-times the inflation pressure
and makes the cryoballoon more rigid/less-compliant and slightly
increases the cryoballoon size. Compared to the Boston Scientific
design, the inflation pressure of the cryoballoon stays fairly constant
and low even during the ablation phase. Aside from the minor differences
in the refrigerant flow rate at different phases of the ablation
process, this pressure difference does significantly change how the
end-user uses the cryoballoon to engages the pulmonary vein antrum: 1)
Cryoballoon-PV antrum contact does not change; what one see during
venogram is what one gets during ablation. There is no need for the
“relook angiogram”. This may lead to a more consistent and
reproducible result of single-shot PV isolation. 2) “Proximal-seal
technique” used to engage the antrum of the PV will yield a different
effect. Can the more compliant system inadvertently allow the user to
produce a less desirable lesion inside the PV? Could the transient
phrenic injury rate be different due to the balloon compliance
difference? 3) Segmental isolation needs may also be different, and the
ability to produce extra-PV antral lesion for large area modification
may also differ in efficacy. Larger studies will be needed to delineate
the differences between the two cryoballoon ablation pressure for PV
occlusion and single-shot PV isolation, while also establishing a safe
procedure with a more compliant cryoballoon.
Many consider the success rate to be the most important outcome of the
procedure. While the study groups are small in this study and can be
difficult to delineate any significant differences. I find patients and
myself to be more concentrated on the complication rate as the most
important outcome of the procedure– success story of a procedure of
course do focus on a great clinical outcome, but avoidance of major
complications for any of our AF treatment remains paramount. Compared to
studies of yesteryears, procedure time of 1-2 hours is now standard, and
many centers are now aiming for the same-day discharge for
straight-forward PV isolation. This speaks to the value of PV isolation
as the first-line therapy for paroxysmal and persistent AF.
New advancement such as variable cryoballoon size, compliance, and
refrigerant distribution will continue to make cryoballoon a more
successful, but more importantly safer, procedure for the treatment of
AF. As several companies are now working on their own cryo-platform
around the world, and this will continue to improve our success and
complication rate. As with any new procedure, what lingers on most
operator’s mind is ability to minimize the complication
rate—establishing dosing and handling technic that may be unique to
each of the cryo platform to maintain procedural safety.
REFERENCES
- Calkins H, Hindricks G, Cappato R, et al. 2017
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- Su W, Kowal R, Kowalski M, et al. Best practice guide for cryoballoon
ablation in atrial fibrillation: The compilation experience of more
than 3000 procedures. Heart Rhythm. 2015; 12(7): 1658-66.
- Su W, Aryana A, Passman R, et al. Cryoballoon Best Practices II:
Practical guide to procedural monitoring and dosing during atrial
fibrillation ablation from the perspective of experienced users. Heart
Rhythm. 2018; 15(9): 1348-1355.
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