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\begin{document}

\title{Selection of Patients for Hybrid Ablation Procedure}



\author[1]{David DeLurgio}%
\affil[1]{Emory Saint Joseph's Hospital}%


\vspace{-1em}



  
  \date{May 27, 2024}


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\selectlanguage{english}
\begin{abstract}
Catheter ablation for treatment of symptomatic non-paroxysmal atrial
fibrillation remains challenging. Clinical failure and need for
continued medical therapy or repeat ablation is common, especially in
more advanced forms of atrial fibrillation. Hybrid ablation has emerged
as a more effective and safe therapy than endocardial-only ablation
particularly for longstanding persistent atrial fibrillation as
demonstrated by the randomized controlled CONVERGE trial. Hybrid
ablation requires collaboration of electrophysiologists and cardiac
surgeons to develop specific workflows. This review describes the Hybrid
Convergent approach in the context of available ablation options and
offers guidance for workflow development and patient selection.%
\end{abstract}%



\sloppy


Selection of Patients for Hybrid Ablation Procedure

David B. De Lurgio, MD

David B. De Lurgio, MD Emory University Emory St. Joseph's Hospital

Suite 300 5671 Peachtree Dunwoody Rd Atlanta, GA 30342 Email
ddelurg@emory.edu

\textbf{Disclosures:} Dr. De Lurgio is a consultant and speaker for
AtriCure and Boston Scientific, as well as a consultant to Medtronic.

\textbf{Word Count:} 4364

\textbf{Sources of Funding:} None



\textbf{Abstract}

Catheter ablation for treatment of symptomatic non-paroxysmal atrial
fibrillation remains challenging. Clinical failure and need for
continued medical therapy or repeat ablation is common, especially in
more advanced forms of atrial fibrillation. Hybrid ablation has emerged
as a more effective and safe therapy than endocardial-only ablation
particularly for longstanding persistent atrial fibrillation as
demonstrated by the randomized controlled CONVERGE trial. Hybrid
ablation requires collaboration of electrophysiologists and cardiac
surgeons to develop specific workflows. This review describes the Hybrid
Convergent approach in the context of available ablation options and
offers guidance for workflow development and patient selection.

\textbf{Keywords:}

Longstanding persistent atrial fibrillation

Hybrid ablation

Convergent procedure



\textbf{Introduction}

Atrial fibrillation (AF) is the most common cardiac arrhythmia, with
estimates that over 37 million people were impacted globally in 2017 and
that number is expected to continue to rise. Future estimates of AF
burden predict an increase of over 60\% by the year 2050, with 6-12
million patients in the US alone.\textsuperscript{1} Not only is AF a
major risk factor for ischemic stroke, but it also causes economic
burden, significant morbidity, and
mortality.\textsuperscript{1}Non-paroxysmal AF, or continuous AF
sustained longer than 7 days, is associated with higher rates of
thromboembolism (TE) and mortality compared to paroxysmal AF based on a
meta-analysis of 12 studies.\textsuperscript{2} Treatment options for
paroxysmal AF include antiarrhythmic drugs (AADs), cardioversion, and
ablation.\textsuperscript{3} While the first line of therapy for
paroxysmal AF is often AADs, a meta-analysis of 6 trials indicated that
ablation was more effective and reducing arrhythmia recurrences and
hospitalizations with a similar safety profile as that of
AADs.\textsuperscript{4} Unfortunately, AAD and ablation options for
non-paroxysmal AF have lesser and varying levels of success such that
many patients find themselves with long durations of AF or experience
recurrent AF that has to be re-addressed.\textsuperscript{5,6}Trials
have demonstrated improved quality of life with ablation versus only
AADs in patients with non-paroxysmal AF\textsuperscript{7}, who are
typically patients that have failed AAD treatment, thus leading to
decisions on the type of ablation based on the individual patient's
clinical history and current clinical picture.

Collaborative heart teams must discuss the individual characteristics
and specifics surrounding each patient with AF seeking care to determine
the best course of treatment.\textsuperscript{8} With this approach, the
role of the collaborative heart team is to determine patient selection
based on their need or lack of need for concomitant surgery,
risk/benefit, compliance, and other patient specific factors. Although
AADs are still often the first line of defense, they are frequently
ineffective or poorly tolerated. Options for cardiac ablation to treat
AF have expanded over time, with both approved and emerging catheter,
surgical, and hybrid epicardial-endocardial techniques supported by
clinical evidence. Determining the patient groups most likely to benefit
from each of these approaches allows the multi-disciplinary team to
select the best treatment option for a particular patient. The focus of
this review is on Hybrid Convergent ablation, a minimally invasive,
closed chest combined epicardial-endocardial approach, and the selection
of patients most appropriate and most likely to benefit from this
procedure.

\textbf{Surgical Ablation}

There are several cardiac ablation options for AF treatment that may be
considered: surgical, endocardial only, or hybrid ablation. While the
focus of this review is on hybrid ablation, surgical and endocardial
ablation are described briefly as relevant for patient selection.
Surgical ablation is typically utilized when there is a concomitant
open-heart surgery for a structural issue coupled with pre-existing AF.
It is done via a median sternotomy or a right thoracotomy, both of which
require the patient undergo cardiopulmonary bypass, which is why it is
typically reserved for those undergoing cardiac surgery for concomitant
structural heart issues. The surgical ablation technique that is
considered by many to be the gold standard is the Cox-Maze procedure,
which involves bi-atrial ablation including isolation of the pulmonary
veins and left atrial posterior wall as well as left atrial appendage
(LAA) exclusion.\textsuperscript{9}Published studies have reported high
long-term success rates to restore sinus rhythm and mortality benefits
of Cox-Maze surgical ablation. Other surgical ablation approaches may
utilize reduced lesion sets including those focused only on the left
atrium or epicardial only ablation, which may not achieve transmurality.
Several societies have designated concomitant surgical ablation as a
Class I recommendation to perform concomitantly during structural heart
procedures such as valve repair/replacement or
CABG.\textsuperscript{10-12} However despite these recommendations, a
study of almost 80,000 patients over three years from a 2014 Medicare
database indicated that an average of 22\% of patients had concomitant
AF surgical ablation, with rates varying by specific surgery
type.\textsuperscript{13} Badhwar et al report an increase from 52\% to
61.5\% of patients undergoing surgical ablation concomitant with AF at
the time of mitral valve repair in an analysis of the Society of
Thoracic Surgeons database.\textsuperscript{10}

\textbf{Endocardial Ablation}

Standalone endocardial catheter ablation is less invasive than surgical
concomitant ablation and involves a catheter being guided through venous
access points, entering the right atrium, and ultimately the left atrium
where the endocardial ablation is performed. Patients with paroxysmal AF
have higher success rates, such as freedom from atrial arrhythmias and
less recurrences of repeat ablations compared to those with
non-paroxysmal AF. After a secondary repeat ablation, paroxysmal AF
patients experienced over 92\% freedom from AF, whereas patients with
persistent AF and long-standing persistent AF had lower secondary
success rates of 88.1 and 80.9\%, respectively.\textsuperscript{14} In a
single center study, long-term success rates ranged from 28.4 to 51.1\%
recurrence-free rates after a single or three procedures, respectively,
leaving a large percentage of patients with failed
treatment.\textsuperscript{15} While contemporary trials have
demonstrated that radiofrequency catheter and cryoballoon endocardial
ablation may yield sufficient clinical outcomes for paroxysmal AF and
even non-paroxysmal AF without advanced substrate, there are patients
with advanced AF who tend to be more difficult to treat and have lower
success rates and consequently more subsequent procedures after
endocardial ablation.\textsuperscript{14} Recent studies of persistent
AF have demonstrated rates of effectiveness of 54.8\% to 61.7\% at 12
and 15 months, respectively, after a single ablation
procedure.\textsuperscript{16,17}Tsai et al. recently published longer
term follow up results from a Taipei hospital. After a single index
ablation procedure, 100 patients with non-paroxysmal AF were followed
very-long-term for over 5 years with a target follow up of 10 years.
Only 16\% of patients remained free of AF at 10 years, with the majority
of AF recurrence (61.9\%) at the one year mark, emphasizing the need for
more effective and enduring treatment options for non-paroxysmal
AF.\textsuperscript{18}

\textbf{Hybrid Ablation}

With such a large population undertreated or with failed treatment for
advanced AF, including long-standing persistent AF, there is still an
unmet need to find better treatment options that provide durable and
long-lasting treatment. Hybrid epicardial-endocardial procedures are
newer, minimally invasive ablation approaches that have shown promising
results compared to endocardial ablation techniques. The development of
hybrid ablation techniques seeks to combine the benefits of both
surgical and electrophysiological catheter ablation in a
multi-disciplinary care team approach, while minimizing the risks that
come with both of those procedures alone. Hybrid procedures target both
the endocardial and epicardial left atrium, seeking to ensure durable,
complete transmural lesions on the beating heart. In order to access the
pericardium without an open chest, access to the posterior left atrium
for epicardial ablation is either gained thoracoscopically or
endoscopically through a subxiphoid incision. The latter approach,
sometimes referred to as the Hybrid Convergent procedure, is the focus
of this review.

Several single center studies have been published describing the
mid-term outcomes of the Hybrid Convergent
procedure.\textsuperscript{19,20}The CONVERGE clinical trial, a
multicenter randomized controlled trial that evaluated the safety of the
Hybrid Convergent combined ablation treatment and its effectiveness
versus standard endocardial ablation in the persistent and long-standing
persistent AF patients. Based on these results, the Hybrid Convergent
procedure using the EPi-Sense device (AtriCure, Inc.) for epicardial
ablation augmented by endocardial catheter ablation is the only
FDA-approved minimally invasive treatment for longstanding persistent
AF.

\textbf{Hybrid Procedure Overview and Lesion Set}

In the Hybrid Convergent procedure (Figure 1), a multidisciplinary heart
care team approach is utilized, first with a surgeon performing an
epicardial ablation and then with an electrophysiologist following with
an endocardial ablation. The minimum aspects of this lesion set involve
electrical isolation of the posterior wall and pulmonary veins, with
esophageal heating mitigated by device design and procedural best
practices. The epicardial ablation procedure is focused on the posterior
wall, utilizing a vacuum-assisted unipolar radiofrequency device
inserted through a cannula with an endoscope. A transdiaphragmatic or
more commonly a subxiphoid approach is used to access the pericardium.
Epicardial ablations are applied across the posterior wall of the left
atrium creating contiguous, parallel lesions. Current convergent
ablation relies on the homogenization of the posterior wall in a more
simplified manner complementary to the endocardial ablation as opposed
to prior versions that were more extensive to replicate a Maze-like
lesion set including a posterior wall box and bi-atrial
lesions.\textsuperscript{21} Following the epicardial ablation by the
surgeon, endocardial mapping guides the endocardial ablation performed
using an irrigated radiofrequency catheter by the electrophysiologist,
connecting any breakthrough gaps in lesions and thus completely
isolating the left and right pulmonary veins. Confirmation of isolation
is done by evaluating entrance and/or exit block to ensure the absence
of conduction. Most studies on hybrid convergent procedures relied on
commercially available radiofrequency endocardial catheters.
Retrospective single-center and registry analyses have reported the
safety and efficacy of endocardial cryoballoon catheters in the Hybrid
Convergent procedure.\textsuperscript{22-24}

\textbf{Single vs Staged Setting}

The Hybrid Convergent procedure relies on procedures performed both by a
surgeon and an electrophysiologist. These components can either be done
in a single setting in a hybrid OR-electrophysiology lab or separate OR
and electrophysiology lab, or in a staged setting with the two stages
usually at least 30 days apart. Whether single setting or staged, the
epicardial portion is always first, followed by the endocardial portion.
A robust comparison of the clinical outcomes of single versus staged
Hybrid Convergent procedures has not yet been performed, however the
choice may be influenced by physician and patient preferences,
institutional practices, and schedule feasibility.

The CONVERGE trial was a multi-center randomized controlled trial to
evaluate the safety and effectiveness of Hybrid Convergent versus
endocardial catheter ablation in advanced AF.\textsuperscript{24} With
no restrictions on duration of persistent AF at enrollment, this ensured
long-standing persistent AF patients were a substantial portion of the
enrolled subjects (42\%), which no other trial has done to date. The
primary endpoint was to determine the freedom from AF/atrial
flutter/atrial tachycardia off new or increased dose of previously
failed AADs through 12- months. In the Hybrid Convergent group, 67.7\%
of patients achieved the primary effectiveness endpoint compared to
50.0\% in the catheter ablation group, with a significant absolute rate
difference of almost 17.7\%, favoring Hybrid Convergent (risk
ratio=1.35, p=0.036). In various sub-analyses by AAD usage, Hybrid
Convergent had a higher success rate than catheter ablation in almost
all instances and was deemed clinically although not statistically
significant for patients off amiodarone. The Hybrid Convergent arm
consistently demonstrated significantly better AF burden reduction and
freedom from AF at 12 and 18 months compared to the Catheter Ablation
Arm.\textsuperscript{24}

\textbf{Long-Standing Persistent AF}

The progression of AF from paroxysmal to long-standing persistent AF is
characterized by advanced substrate remodeling of the left atrium in a
stretch, inflammation, and fibrosis sequence leading to
fibrillation.\textsuperscript{25} Thus, in advanced AF, the predominant
triggers have evolved from the pulmonary vein to left atrial tissue,
particularly on the posterior wall, creating a need for treatment
options beyond endocardial ablation to effectively and comprehensively
treat long-standing persistent AF.\textsuperscript{26,27}Success rates
of endocardial ablation in this population have had limited
effectiveness, ranging from 35.6 to 43\% after a single
procedure.\textsuperscript{26,27}This is attributed to the lack of a
standardized lesion set, limited ability to produce transmural lesions,
and dissociation of electrical activity between the endocardium and
epicardium. A subgroup analysis examining the effectiveness of the
Hybrid Convergent procedure for long-standing persistent AF demonstrated
an absolute difference of 28.8\% (78\% improvement; p=0.022) in 12-month
freedom from AF in the Hybrid group over the endocardial only group and
was sustained through 18-months.\textsuperscript{28} The benefit of
Hybrid Convergent held when compared to the Catheter Ablation arm and
their respective impacts on AF burden reduction as well as freedom from
cardioversion and AF symptoms, through 18-months. Along with an
acceptable safety profile, these significantly improved outcomes
provided the collaborative heart team a new, effective approach for the
difficult to treat population of patients suffering from advanced AF.

\textbf{Other Considerations for Hybrid Convergent Patient Selection}

Recent studies have demonstrated that there are several clinical
characteristics of patients who may benefit from Hybrid Convergent over
AADs or endocardial ablation, absent an indication for a concomitant
surgical ablation or contraindication. These include those with forms of
advanced AF; patients in whom there is a desire to simultaneously manage
the left atrial appendage (LAA)/Ligament of Marshall (LOM); patients who
have failed prior catheter ablation; and others with specific
considerations such as esophageal risk.

\textbf{Advanced AF}

In addition to the CONVERGE post-hoc analysis for LSPAF, other studies
have demonstrated favorable success to eliminate atrial arrhythmia or
maintain normal sinus rhythm in patients with longstanding persistent
AF.\textsuperscript{23,29}Classification of AF by duration alone is
arbitrary and can be challenging based on incomplete patient history or
available rhythm monitoring. There is emerging evidence that other
factors associated with advanced AF may characterize patients who could
benefit from Hybrid Convergent ablation.\textsuperscript{23,29}

Left atrial (LA) size has been shown to be related to the recurrence of
AF after endocardial ablation.\textsuperscript{30} Most studies have
defined enlargement by atrial diameter although a meta-analysis of 22
studies that due to the asymmetry of the LA and thus LA dilation, LA
diameter may be an underestimate of size and LA volume is more accurate
in predicting AF recurrence and even new onset AF.\textsuperscript{31}
Because the imaging modalities vary in the precision of their estimates
of left atrial size, the mean difference in larger atria associated with
the risk of AF is actually quite small so this must be a consideration
in determining the accuracy of LA size measurements. Of the 22 studies
in the meta-analysis by Zhuang, et al, the mean LA diameter reported at
baseline was 34.3-49mm, partly beyond normal range. Only 3 studies were
identified that solely examined non-paroxysmal AF, for a total of 143
patients. The mean atrial size in those studies ranged from
45-49mm.\textsuperscript{30} The CONVERGE trial allowed patients with
left atrial diameter up to 6.0 cm, with the mean left atrial diameter in
the Hybrid Convergent arm of 4.4 cm (44mm).\textsuperscript{32} With an
increased risk of developing recurring AF, patients with enlarged left
atria might be best served by Hybrid Convergent ablation versus a
catheter ablation that may result in recurrences and repeat ablations.

\textbf{AF Associated with Heart Failure}

The co-mingling of heart failure and AF was examined in a review of
patients in the Framingham Heart Study enrolled between 1980 and
2012.\textsuperscript{33} More than half of those with heart failure
also had AF, typically with AF preceding rather than following heart
failure. Of those with AF, more than a third had heart failure, which
typically developed after the onset of AF. Regardless of the temporality
between the two conditions, the increased morbidity and mortality when
present together is increased compared to individual
diagnoses.\textsuperscript{34}Patients in heart failure with a reduced
ejection fraction and concurrent AF have had also had low success with
medical therapy including AADs and rate control medications. CASTLE-AF
showed that catheter ablation for patients with paroxysmal or persistent
AF, HF, and left ventricular dysfunction significantly lowered composite
death and hospitalizations, improved left ventricular ejection fraction,
and reduced AF burden compared to medical therapy. However, the patient
population in the trial was highly selected, which potentially limits
the applicability to real world practice.\textsuperscript{35,36}Patients
with LVEF \textless{}40\% were excluded from CONVERGE and the mean LVEF
in the Hybrid Convergent arm was 55\%. Thus, patients with reduced LVEF
were thought to be out of bounds for Hybrid convergent treatment.
However, recently there has been interest in determining if a hybrid
approach could successfully treat AF and subsequently improve LVEF in
patients with reduced LVEF at baseline. Our multi-center retrospective
analysis of patients included those presenting with severely reduced
baseline LVEF ([?]40\%) and showed significantly improved LVEF after
Hybrid Convergent treatment. Kiankhooy et al. used a thoracoscopic
hybrid approach for patients with depressed EF and tachycardia mediated
cardiomyopathy, which demonstrated feasibility and significantly
improved ejection fraction after treatment at a mean of 3.5 years (\selectlanguage{ngerman}±1.9
years) follow-up and improvement in NYHA Class from
baseline.\textsuperscript{37}

\textbf{Left Atrial Appendage (LAA)/Ligament of Marshall}

As previously discussed, patients with advanced AF have more
non-pulmonary vein triggers, such as the posterior wall, and this can
also include the LAA and Ligament of Marshall (LOM).\textsuperscript{38}
Excluding the LAA at the time of the hybrid epicardial ablation stage
can address a site of AF triggers through electrical isolation as well
eliminating a predominant site of thrombus in AF.\textsuperscript{39}
The addition of LAA exclusion is often performed in hybrid thoracoscopic
ablation, which is the subject of several clinical trials (NCT01246466;
NCT02695277; NCT02441738). The LAA exclusion technique involves
epicardial clip exclusion of the LAA by a simultaneous left
thoracoscopic approach.\textsuperscript{39} In the absence of randomized
controlled trial data evaluating the effectiveness and safety of Hybrid
Convergent with LAA exclusion, multi-disciplinary care teams are using
the available evidence and determining patient selection for whom they
feel the benefit-risk profile is acceptable to proceed with this
approach.\textsuperscript{40} In a study over 6 years, 139 patients with
persistent AF and no history of prior ablation underwent a Hybrid
convergent procedure. In April 2016, LAA exclusion was added to the
study procedures. Of the 139 patients, 59 had only Hybrid ablation and
64 had the concomitant Hybrid ablation with LAA exclusion. Both groups
were similar with respect to age and gender as well as BMI, which was
elevated in both groups (\textgreater{}32). In the Hybrid plus LAA clip
group, the patients appeared to have a longer time since AF diagnosis
although not statistically significant (mean of 6.4 years vs 4.6 years;
p=0.15). Other baseline data and comorbidities were similar between the
groups. The Hybrid plus LAA exclusion group had a greater freedom from
AF recurrent compared to Hybrid ablation only group (77\% vs 58\%;
p=0.04).\textsuperscript{41}

Initially described by British surgeon John Marshal in the 1800s, the
LOM and Vein of Marshall (VOM) are remnants of the embryonic left
superior vena cava with the VOM enclosed within the
LOM.\textsuperscript{42,43}The cluster of nerve cells known as the
autonomic ganglionated plexi are found in abundance in the epicardial
fat, embedded along the Ligament of Marshall, near the pulmonary
vein-left atrial junctions. This composition of the epicardial fat
stimulates triggers, enabling the perpetuation of
AF.\textsuperscript{44}If the ablation procedure is expanded to include
targeting the GP specifically located in the LOM in addition to PVI,
this may improve the success rates in patients with paroxysmal as well
as persistent AF.\textsuperscript{45} These ganglionated plexi are also
implicated in left atrial remodeling and substrate changes, commonly
found in more progressive forms of AF.\textsuperscript{46} In a study
examining the effect of ethanol infusion added to the VOM during
catheter ablation in persistent and long-standing persistent AF,
patients receiving the combined catheter and VOM ethanol infusion had
higher rates of freedom from AF vs the catheter only group (49.2\% vs
38\%; p=0.04). Due to the LOM harboring the source of AF and AT
triggers, targeting this anatomical region rich with theses ganglionated
plexi during epicardial ablation along with LAA exclusion is of
increasing interest.\textsuperscript{47}

\textbf{Prior Failed Catheter Ablation}

Posterior wall isolation is part of the complex strategy of managing
advanced AF, in addition to PVI, however it is often difficult to
achieve safely with only endocardial catheter ablation. This is due to
the thickness of the roof of the posterior wall of the left atrium and
because of the need for long connection lines between the roof and the
floor of the atrium, to create the conduction block without a gap. The
lower linear lesion line at the floor of the posterior wall is more
difficult to create due to the proximity of the esophagus and risk of
esophageal damage.\textsuperscript{48} In a study of patients undergoing
left atrial posterior wall isolation concomitant with pulmonary vein
reisolation, feasibility of isolating the LAPW with endocardial ablation
was successfully demonstrated, despite no outcome differences in
improvement of freedom from atrial arrhythymias compared to pulmonary
vein reisolation alone. Of the 196 AF patients in the study, 103 were in
the LAPW plus PV reisolation group and 36 patients (35\%) required
additional ablation within the center ``box'' of the
LAPW.\textsuperscript{49}This brings increased risk to endocardial
catheter ablation but has potential to be easier and safer utilizing a
Hybrid ablation approach such as those with advanced AF presenting for
repeat ablation treatment. In patients with advanced AF and a need to
isolate the posterior wall, a hybrid ablation approach may have the
advantage of better access to completely and safely isolate it primarily
through epicardial ablation applying energy towards the heart followed
by endocardial touchup to address any gaps particularly near the
pericardial reflections. This provides a more comprehensive treatment to
prevent recurrence resulting from multiple triggers, including the
pulmonary vein, left posterior wall, and endocardial tissue.

While the CONVERGE trial excluded patients with prior ablations, in
routine clinical practice many patients with advanced AF have undergone
prior catheter ablation attempts yet are still experiencing AF
recurrences. A recent meta-analysis of Hybrid Convergent ablation
studies included three studies in which one-third of the total patients
had prior catheter ablation. Mannakkarra et al. recently reported their
single-center experience with Hybrid Convergent ablation, including 38\%
of patients who had received prior catheter ablation at
baseline.\textsuperscript{20} However, to date, only one study has
directly compared outcomes of patients who received Hybrid Convergent as
a de novo versus previous catheter ablation, finding there was no
difference in arrhythmia recurrence.\textsuperscript{22}Additionally,
there may be a cumulative benefit in that those with prior ablations
require less endocardial PV isolation and were more likely to convert to
sinus rhythm during the Hybrid procedure compared to those with no prior
ablation history.\textsuperscript{22} Kress et al. reported 75.0\% of
patients with prior ablation needed endocardial PV isolation, which was
significantly less than 97.9\% of patients who received hybrid ablation
as a first ablation procedure (p\textless{}0.001). Additionally, fewer
patients who had prior ablation needed cardioversions (26.7\%) to
achieve sinus rhythm intraprocedurally compared to those receiving
hybrid ablation as a first ablation procedure (45.8\%, p=0.038). With
few comparative studies or studies exclusively looking at hybrid
convergent ablation after previous catheter ablation patients, more
research as well as additional cumulative real-world evidence is
necessary to determine whether there are any significant differences in
procedural and treatment outcomes.\textsuperscript{19}

\textbf{Other Considerations}

The risk of atrioesophageal fistula remains a major concern with
endocardial ablation involving the left atrial posterior wall.
Endocardial ablation of non-paroxysmal atrial fibrillation often
involves significant energy application in the vicinity of the
esophagus, particularly when complete isolation of the posterior wall is
a goal. Esophageal temperature monitoring is routinely used, but
guidelines for acceptable temperature deviation are lacking. Further,
evidence that temperature monitoring prevents esophageal injury is
limited, as evidenced by the continued incidence of this terrible
complication. The Hybrid Convergent procedure benefits from a unique
catheter design which directs energy away from the esophagus and toward
the epicardial left atrial posterior wall. In addition, the pericardial
space is irrigated with saline during energy application. Far less
endocardial ablation is required near the posterior wall to complete the
lesion set. These factors result in less esophageal heating, and
presumable a lower risk of esophageal injury. The ability of the
Convergent procedure to provide durable transmural left atrial posterior
wall isolation while minimizing risk of esophageal injury may be an
important consideration in patient selection.

\textbf{Relative Contraindications}

There are several groups of patients who may be contraindicated for
hybrid procedures or who may be deemed riskier and potentially have a
longer recovery time. As with other surgical procedures, patients with
gastroesophageal reflux disease, severe renal insufficiency, in ability
to tolerate anesthesia, acute infection such as sepsis/systemic
infection, endocarditis, and localized surgical site infections.
Additionally, there are several factors that disqualify a patient as a
candidate specific to Hybrid Convergent ablation. Patients with a prior
pericardiotomy have scar tissue formed around the heart and between the
heart and surrounding structure, including the lungs. This makes future
heart surgeries and procedures more challenging and thus are not
recommended for hybrid approaches. The presence of a left atrial
thrombus brings an increased risk of stroke and thromboembolism
surrounding catheter ablation procedures. Thus, these patients should be
treated with oral AADs for at least 3 weeks with a repeat
transesophageal echocardiogram or other non-invasive multimodality
imaging before considering a hybrid ablation
procedure.\textsuperscript{8}

\textbf{Future directions}

There are several factors that a multi-disciplinary hybrid team, led by
the partnership between the electrophysiologist and cardiac surgeon,
should consider when assessing a patient for potential Hybrid Convergent
treatment. First, the care team should ensure that it is comprised of
several specialists working together to promote a robust AF care team
model to optimize care of this patient population. There should be a
referral process in place that transitions patients from the single
electrophysiologist practitioner to this shared care team model that is
expanded to also include cardiac surgeons and cardiovascular
anesthesiologists, among others, where each member provides individual
expertise. The Hybrid Convergent procedure does not come without risks,
so several patient factors must be assessed, such as chronicity of AF,
left atrial size, and other comorbidities. If the efficacy of the
procedure is expected to be low and the risks high, other treatment
options may be considered first. If other treatment options have been
tried and were not successful or there has been a recurrence of AF, the
team may weigh the potential benefits of the Hybrid convergent procedure
greater than the potential risks of the procedure itself or the risks of
other or no treatment.

As previously mentioned, additional, larger studies could evaluate the
potential arrhythmia and thromboembolic benefit as well as any risks
associated with LAA exclusion in a hybrid convergent procedure. This
would be helpful to guide further procedural and patient selection best
practices for closing the LAA in the context of hybrid ablation. Matched
comparisons of patients who had prior ablation and those who received de
novo Hybrid Convergent ablation would help determine how successful the
procedure is for patients outside of the CONVERGE trial target
population. While CONVERGE allowed left atrial size up to 6.0 cm, the
enrolled patient population had mildly enlarged left atrium. Upper
limits for left atrial size have been established for open surgical
ablation based on the rhythm benefit achieved, however it is currently
unknown how Hybrid Convergent outcomes correlate with incremental
increases in left atrial size.

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\textbf{Acknowledgements}

Marcie Meador, PhD (AtriCure, Inc.) and Kristen Plasseraud, PhD
(AtriCure, Inc.) provided medical writing and editing assistance under
the direction of Dr. De Lurgio.

\textbf{Disclaimer}

The EPi-Sense Guided Coagulation System is intended for use in treating
symptomatic long-standing persistent atrial fibrillation when augmented
in a hybrid procedure with an endocardial catheter listed in the IFU, in
patients: 1. Who are refractory or intolerant to at least one Class I
and/or III antiarrhyhmic drug and 2. In whom the expected benefit from
rhythm control outweighs the potential known risks associated with a
hybrid procedure such as delayed post-procedure inflammatory pericardial
effusions.

\textbf{Figure 1} . Hybrid Convergent Epicardial and Endocardial Lesion
Pattern\selectlanguage{english}
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