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\begin{document}

\title{A Second Cryoballoon System- new and improved?}



\author[1]{Wilber Su}%
\affil[1]{Banner - University Medical Center Phoenix}%


\vspace{-1em}



  
  \date{May 22, 2024}


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\begin{abstract}
Generations of cryoballoon transformed the atrial fibrillation ablation
landscape. New advancements continue to make cryoballoon more successful
and safer treatment. A new cryoballoon PolaRx from Boston Scientific has
unique features compared to that of the Medtronic Arctic Front Advance
system. Comparison of the two available cryoballoons will require
ongoing larger trial and clinical experience.%
\end{abstract}%



\sloppy


\textbf{A Second Cryoballoon System- new and improved?}

Wilber W. Su MD\textsuperscript{1,2}

Banner-University Medical Center, Phoenix, AZ

Stanford University Medical Center, Palo Alto, CA

\textbf{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 Front\textsuperscript{TM} Cryoablation System has been
popularized world-wide, with over 700,000 cases performed to date and
vast clinical experience and expanded
indications.\textsuperscript{1}Technique, dosing, and best practices to
avoid complications has also improved with the Arctic Front Advance
cryoballoon over the past 15 years.\textsuperscript{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 Advance\textsuperscript{TM} versus the Boston
Scientific PolaRx\textsuperscript{TM} 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
(\emph{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.\textsuperscript{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

\begin{enumerate}
\tightlist
\item
  Calkins H, Hindricks G, Cappato R, et al. 2017
  HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and
  surgical ablation of atrial fibrillation. Heart Rhythm. 2017; 14(10):
  e275-e444. doi: 10.1016/j.hrthm.2017.05.012.
\item
  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.
\item
  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.
\item
  Kuck K, Brugada J, Albenque J. Cryoballoon or Radiofrequency Ablation
  for Atrial Fibrillation. N Engl J Med. 2016 Sep 15;375(11):1100-1.
  doi: 10.1056/NEJMc1609160. PMID: 27626535.
\item
  Getman MK, Wissner E, Ranjan R, Lalonde JP. Relationship between
  time-to-isolation and freeze duration: Computational modeling of
  dosing for Arctic Front Advance and Arctic Front Advance Pro
  cryoballoons. J Cardiovasc Electrophysiol. 2019 Nov;30(11):2274-2282.
  doi: 10.1111/jce.14150. Epub 2019 Sep 17. PMID: 31502304; PMCID:
  PMC6899473.
\end{enumerate}

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