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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3849_Библиотеки_им_академика_М_И_Перельмана
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D. T. Huang and T. Prinzi
along the ablation line. If block is not present, careful and detailed
activation mapping along the ablation line should show where
electrical activity is still sneaking through the line of block, and
this can serve as a guide to nish ablation. The voltage map of the
region can be used to observe where tissue along the line is still
active with a substantial voltage mapped and serve as another
guide to complete the ablation.
Validation can be more complex with atypical utter ablation
lines, but applying the same principle used in the criteria for typical utter ablation can be adopted to demonstrate bidirectional
block across the associated critical isthmus in atypical utter
cases. By placing catheters on either side of the created line of
block and pacing in both directions, bidirectional block across the
linear lesion can be conrmed with these additional activation
maps.
References
1. Granada J, Uribe W, Chyou PH, Maassen K, Vierkant R, Smith PN, Hayes
J, Eaker E, Vidaillet H. Incidence and predictors of atrial utter in the
general population. J Am Coll Cardiol. 2000;36(7):2242.
2. Wells JL Jr, MacLean WA, James TN, Waldo AL. Characterization of
atrial utter. Studies in man after open heart surgery using xed atrial
electrodes. Circulation. 1979;60:665.
3. Saoudi N, Cosio F, Waldo A, et al. A classication of atrial utter and
regular atrial tachycardia according to electrophysiological mechanisms
and anatomic bases; a Statement from a Joint Expert Group from The
Working Group of Arrhythmias of the European Society of Cardiology
and the North American Society of Pacing and Electrophysiology. Eur
Heart J. 2001;22(14):1162.
4. DePonti R. Treatment of macro-re-entrant atrial tachycardia based on
electroanatomic mapping: identication and ablation of the mis-diastolic
isthmus. Eur Secur. 2007;9:449–57.
5. Tada H, Oral H, Sticherling C, et al. Double potentials along the ablation
line as a guide to radiofrequency line as a guide to radiofrequency ablation of typical atrial utter. J Am Coll Cardiol. 2001;38(3):750.
A Practical Guide
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toCatheter Ablation
ofAtrial Fibrillation
JoshuaHaswell, TravisPrinzi,
andBurrHall
Abstract
Atrial brillation (AF) remains the most common cardiac
rhythm disturbance encountered in clinical practice, with rising prevalence over the past 50years (Lip Gregory etal. Heart
93:542-3, 2007; Kornej etal. Circ Res 127:4-20, 2020; Mou
etal. Circ Arrhythm Electrophysiol 11:e006350, 2018). With
antiarrhythmic drugs limited by efcacy and side effects, ablation via pulmonary vein isolation (PVI) has become an increasingly common and successful management strategy to control
patient symptoms and, in certain populations, lessen morbidity
and mortality (Marrouche etal., N Engl J Med 378:417–427,
2018). In this chapter we discuss appropriate patient selection
for PVI ablation, the present and upcoming energy modalities
used in clinical practice (namely radiofrequency, cryogenic,
and pulsed-eld), consideration of non-pulmonary vein targets
including isolation of the posterior left atrial wall or the vein of
Marshall, as well as common procedural complications and
strategies to mitigate them including management of periprocedural anticoagulation. We demonstrate a practical step-by-
8
J. Haswell · T. Prinzi · B. Hall (*)
University of Rochester Medical Center, Rochester, NY, USA
e-mail: Burr_Hall@urmc.Rochester.edu
© The Author(s), under exclusive license to Springer Nature
Switzerland AG 2023
D. T. Huang et al. (eds.), Cardiac Electrophysiology in Clinical
Practice, In Clinical Practice,
https://doi.org/10.1007/978-3-031-41479-4_8
147
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J. Haswell et al.
step guide to AF ablation including anatomical orientation,
transseptal puncture, pulmonary vein access, catheter manipu-
lation within the left atrium, and successful ablation guided by
intracardiac echocardiography (ICE), uoroscopy, three-
dimensional electro anatomical mapping, and additional
industry-specic tools.
Keywords
Atrial brillation · Pulmonary vein isolation · Catheter ablation
Radiofrequency · Cryoballoon · Intracardiac echo
Introduction
Atrial brillation (AF) continues to be the most common cardiac
rhythm disturbance encountered in clinical practice. In 2016, The
Global Burden of Disease Project estimated a worldwide prevalence of AF around 46.3 million individuals. It is estimated that in
the United States alone, there will be between 6 and 16 million
individuals with a diagnosis of AF by the year 2050. Based on
data from the Framingham Heart Study, the prevalence of AF has
increased three-fold over the last 50years. The lifetime risk estimates for atrial brillation are now 1in 3 for white individuals
and 1in 5 for black individuals [1–3].
Antiarrhythmic drugs can reduce the number of AF episodes
and duration, but overall have limited efcacy and are often poorly
tolerated by a signicant percentage of patients. Pulmonary vein
isolation (PVI) is now considered to be a safe and effective therapy in patients with symptomatic atrial brillation. The primary
goal of AF ablation is to improve patient quality of life by eliminating or signicantly reducing the total burden of AF episodes
and discontinuing antiarrhythmic drug therapy when possible. AF
ablation can also signicantly reduce morbidity and mortality in
certain patient populations; most notably in patients with heart
failure and reduced ejection fraction where AF ablation may be
indicated regardless of the presence or absence of symptoms [4].
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In this chapter we describe how we have been performing ablation for AF over the past 18years at the University of Rochester
Medical Center. While AF ablation technique may vary across
medical institutions, we share our protocol as we have found that
the methods that we describe have served us very well from both
a safety and efcacy standpoint.
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Patient Selection
The primary indication for ablation of AF should be to improve
arrhythmia-related symptoms such as palpitations, fatigue, shortness of breath and exercise intolerance. There is little to no data to
suggest that AF ablation can reduce mortality in patients without
heart failure and reduced ejection fraction, and therefore symptom improvement should be the primary goal of AF ablation. We
have seen patients in our practice with asymptomatic AF who are
interested in proceeding with AF ablation as an alternative to
long-term systemic anticoagulation. The challenge with such an
approach is that many patients can have a high prevalence of
asymptomatic atrial brillation [5]. It has therefore always been
our practice not to discontinue systemic anticoagulation postablation in patients who have a high risk of stroke as determined
by their CHA2DS2-VASc score regardless of the patient reported
presence or absence of symptoms indicative of recurrent
AF. Patients who have a strong desire to discontinue systemic
anticoagulation should at the very least undergo longer-term monitoring looking for recurrences of atrial arrhythmias. In our practice, we utilize a combination of 14-day Holter monitors, 30-day
mobile cardiac outpatient telemetry monitors, and implantable
cardiac monitors that can record continuously for 3years or more.
Consensus indications for ablation of AF have been well
described in the 2019 AHA/ACC/HRS focused update expert
consensus statement [6]. While these guidelines are very helpful
in determining the appropriateness of AF ablation in a specic
patient cohort, it is also imperative that patient preference be carefully considered. AF ablation is a complex procedure with procedural risk, and the risk/benet ratio of performing such a procedure
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Table 8.1 Patient selection for AF ablation
Patient characteristic Better candidate Worse candidate
Symptoms Highly
Symptomatic
Failed Class I or III
antiarrhythmic drugs
AF classication Paroxysmal Long standing
Age at time of ablation Younger (<70) Older (>70)
Left atrial size <80cc >120cc
Concomitant cardiac disease No Yes
Pulmonary disease No Yes
Obstructive sleep apnea No Yes
Obesity No Yes
Prior stroke No Yes
>1 0
J. Haswell et al.
Asymptomatic
persistent
must be carefully considered for each patient. There are many
clinical and imaging-based variables that can be used to help
dene the efcacy and procedural risk of AF ablation in an individual patient, which are summarized in Table8.1.
AF duration is an important predictor of ablation success, with
persistent AF being a known independent predictor of AF recurrence post-ablation compared with paroxysmal AF [7], likely due
to the progressive nature of AF and associated electrical and structural substrate remodeling in the left atrium. Most trials demonstrating the efcacy of AF ablation were performed in the
“paroxysmal” patient population, with the quality and quantity of
data concerning outcomes of AF ablation in the non-paroxysmal
(i.e. persistent or longstanding persistent) patient population
being quite limited. The theory that progressive remodeling of the
left atrium in persistent and longstanding persistent AF leads to
vulnerable substrate for triggers or re-entry in previously-healthy
myocardium has led to multiple attempts to improve the efcacy
of persistent AF ablation by targeting additional non-pulmonary
vein areas for ablation (e.g. isolated complex fractionated atrial
electrograms [CFAEs], linear ablation along the left atrial roof,
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151
oor, or mitral isthmus, ethanol-based ablation of the vein of
Marshall, etc.). Unfortunately, despite numerous well-designed
studies attempting to identify additional ablation targets to consistently improve the efcacy in persistent or longstanding persistent
AF, the results have largely been mixed and PVI remains the cornerstone of therapy. A 2014 meta-analysis suggested that PVI
combined with linear ablation within the left atrium, but not
CFAE ablation, was the most effective strategy [8]. Unfortunately,
this was not borne out in the subsequent STAR AF II trial, which
randomized patients with persistent AF to PVI, PVI plus CFAE
ablation, or PVI plus linear ablation along the left atrial roof and
mitral isthmus and found no improvement over PVI alone [9].
Instead, procedural time was signicantly shorter with a trend
towards increased efcacy in the PVI alone arm. A small randomized clinical trial in 2020 (VENUS) did show some improvement
in efcacy by adding ethanol-based ablation of the vein of
Marshall to standard radiofrequency ablation (PVI in all patients
plus additional targets at operator discretion) [10], but this also
added signicant procedural time and has not yet been sufciently
validated to become routine practice. At our institution, we typically begin with PVI alone and consider additional ablation targets, including posterior wall isolation with roof and oor lines or
less commonly vein of Marshall ablation or mitral lines, for repeat
or complex cases.
In our own experience, we have also found that left atrial volume is a major predictor of AF ablation success. In a subset of 88
patients with both paroxysmal and persistent AF at our institution
undergoing AF ablation, left atrial volume measured by CT
strongly predicted AF recurrence following ablation. The recurrence rate increased from 10% in patients with left atrial volumes
of less than 70cc and increased to over 33% in patients with left
atrial volumes between 110 and 129 cc. In patients with a left
atrial volume of 130cc or larger the recurrence rate after ablation
was more than 90% and appeared to function as a threshold for
failure [11] (Fig.8.1).
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100
CT volume < 70cc
CT volume 70 - 89cc CT volume 90 - 109cc CT vo lume 110 - 129cc CT volume 130cc
% of patients with AF recurrence after ablation
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90
80
70
60
50
40
30
20
10
0
J. Haswell et al.
Fig. 8.1 Failure rate after AF ablation depending on left atrial volume by
CT.As shown in the ROC analysis, the frequency of AF recurrence after ablation increases as left atrial volume increases. The recurrence rate increase
from 10% in patients with small atria with volumes <70cc and increases to
over 33% in patients with left atrial volumes between 110–129cc. A left atrial
volume of at least 130cc, as measured by CT, appears to function as a threshold. Failure rate in patients with a volume of 130cc or larger had an AF recurrence rate of more than 90%
Modalities ofAtrial brillation Ablation
The most commonly used energy sources for isolation of the pulmonary veins are point-by-point radiofrequency (RF) current,
which leads to cellular necrosis by tissue heating, and circumferential cryogenic energy delivered by balloon-based systems to
cause cellular necrosis by tissue freezing. RF ablation commonly
utilizes electro-anatomical mapping systems to decrease the overall uoroscopic time as well as provide additional data on the
underlying left atrial substrate, and offers the exibility of easily
targeting non-pulmonary vein AF triggers or concurrent arrhythmias (e.g. atrial utter) at the time of PVI. Cryoablation offers a
faster procedural time with a shorter learning curve, but is unable
to target non-pulmonary vein triggers and can be associated with
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higher radiation exposure due to commonly-utilized pulmonary
vein angiography to conrm adequate occlusion by the balloon
prior to delivery of cryogenic energy. There are also instances
where patients may have challenging pulmonary vein anatomy on
pre-procedural imaging such as very superior pulmonary vein
ostium or common ostium that may be better treated with radiofrequency ablation. In the case of common ostium, cryoballoon
ablation can still be very effective but may require segmental
freeze lesions on both the superior and inferior aspects of the
common ostium.
Overall safety and efcacy data suggest these two modalities
are similar, with one 2016 randomized trial showing 65% of
patients with symptomatic, drug-refractory paroxysmal AF
remained free from clinical recurrence over a 1.5year mean follow- up [12], and another 2019 study identifying a one-year
freedom- from-recurrence rate of 53% [13]. Both studies showed
no signicant difference with regard to overall safety outcomes.
The lower success rate seen in the latter study was likely driven by
subclinical or asymptomatic AF identied by implantable loop
recorder monitoring, which was employed universally in that
study while the former used periodic electrocardiograms and
Holter monitors to monitor for recurrence. This also highlights
one of the common pitfalls encountered when assessing ablation
success, as the more modest 53% freedom-from-rst-recurrence
rate seen in that study can easily obfuscate the more clinically
relevant decrease in overall AF burden that can be seen following
AF ablation (99% in that case).
Pulsed-eld ablation (PFA) is a promising new ablation modality that may be the next major advance in the eld. Unlike RF or
cryoablation, which achieve cell death by delivery of thermal
energy, PFA is a non-thermal modality that uses high amplitude
pulsed electrical elds to ablate tissue via irreversible electroporation. In this process, the application of a local electrical eld leads
to increased plasma cell membrane permeability and eventual cell
death via induced apoptosis. It has the potential to be delivered
almost instantaneously, taking effect within a single heartbeat
instead of requiring seconds-to-minutes of prolonged contact for
delivery of thermal energy. Cardiomyocytes appear to be particu-
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larly susceptible to irreversible electroporation, whereas nearby
tissues of concern including the esophagus, phrenic nerves, pulmonary veins, and coronary arteries are relatively resistant to
injury [14]. This, combined with the cellular specicity and sparing of the extracellular matrix, has the potential to offer a faster
and safer ablation technology. Initial studies have indeed been
promising with favorable durability and safety outcomes [15], but
this data remains isolated to nonrandomized trials without adequate comparator groups at this time and larger multicenter,
randomized trials are needed before this can be adopted into routine clinical practice.
J. Haswell et al.
Complications ofAtrial brillation Ablation
Over the past decade, there have been signicant improvements in
catheter ablation techniques. Widespread use of intracardiac
echocardiography (ICE), 3-dimensional mapping, steerable
sheaths, contact force catheters and balloon-based technologies
have all played a role in reducing complications. Pericardial effusion, stroke, and atrioesophageal stula formation remain the
most serious complications related to AF ablation. The National
inpatient sample database showed a reduction in complication and
mortality rates from 2011 through 2014 as compared to the time
period from 2000 through 2010. However, this same database
again reported higher complication rates from 2011 through 2014.
This likely reects a larger number of newer and inexperienced
operators performing AF ablation and it is well known that complication rates are signicantly higher in lower volume, less experienced centers [16, 17]. It is encouraging, however, that serious
complications are rare in high-volume centers with extensive
operator experience over time. In an individual high-volume tertiary care referral center, serious complications related to ablation
of atrial brillation were<1% with zero deaths in over 10,000
patients undergoing ablation for atrial brillation. There were no
atrioesophogeal stulas seen in the entire cohort of over 10,000
patients [18].
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Complications associated with AF ablation may be related in
part to regional differences in left atrial transmural wall thickness.
To investigate this, we measured transmural left atrial wall thickness in 34 human heart specimens using calipers in ve anatomic
areas frequently targeted during AF ablation (anterior wall, septum, mitral isthmus, posterior wall, and roof). The roof was the
thinnest region measuring signicantly less than each other area.
The septum was the thickest area [19]. Signicant regional differences exist among the different anatomic areas within the left
atrium and lower power and temperature should be used in anatomic regions known to have thinner transmural wall thickness.
Patients undergoing catheter ablation of atrial brillation are at
increased risk of thromboembolic events during, immediately following, and for several days-to-months after their ablation [20].
The prothrombotic state associated with damaged left atrial endothelium will result in transiently elevated risk of thromboembolism, even in patients previously identied as low-risk for such
events prior to catheter ablation. Anticoagulation can effectively
diminish these risks but carries a prerequisite risk of increased
periprocedural bleeding including access-site complication, cardiac tamponade, or hemothorax. This can make periprocedural
anticoagulant management quite challenging. Patients with a
CHA2DS2-VASc score of at least 2 are generally started on therapeutic anticoagulation at least 3weeks prior to ablation. The use
of warfarin to target an INR 2.0–3.0 was historically a common
strategy for this but is increasingly uncommon at present, particularly after the 2019 AHA/ACC/HRS focused update on management of patients with atrial brillation specically recommended
the use of a non-vitamin K oral anticoagulant (NOAC) over warfarin in NOAC-eligible patients with AF (Class IA) [6]. When
warfarin is still utilized, periprocedural continuation without
interruption or bridging, provided the INR is within therapeutic
range, has become the most accepted practice. This, in part, follows from a large randomized 2014 trial that randomized patients
to uninterrupted warfarin therapy vs discontinuation 2–3 days
pre-ablation with enoxaparin bridging and demonstrated a signicantly higher risk of stroke or TIA in the bridged group compared
to the uninterrupted group (4.9% vs 0.25%) [21]. This same study
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