Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3849_Библиотеки_им_академика_М_И_Перельмана
.pdf
6 Wol-Parkinson-White (WPW) Syndrome
https://t.me/medicina_free
115
One of the biggest pitfalls with mapping in WPW is the possibility of fusion between pathway and nodal conduction, which
can occur when mapping in sinus, atrial paced, and ventricular
paced rhythms. This can be partially avoided by carefully adjusting the rhythm to promote pathway conduction, for example by
accelerating the pacing rate, changing the pacing site to be closer
to the pathway (best demonstrated by comparing the degree of
preexcitation in right vs left atrial pacing at the same cycle length),
or even administering medication (e.g. phenylephrine) to slow AV
nodal conduction. Mapping in AVRT completely eliminates this
concern. Mapping in orthodromic AVRT provides an additional
advantage of crisper ventricular electrograms (due to His-Purkinje
activation), sometimes resulting in more easily interpreted signals. Alternatively, differential pacing from either side of the pathway can be performed so that the electrical wavefront is from the
opposite direction from the presumed path of a slanted pathway.
This technique separates the local electrogram components
resulting in easier interpretation of electrograms and the resulting
map. This approach is also reported to often unmask accessory
pathway potentials, which are appealing targets for ablation.
Regardless of mapping strategy, it is critical to target the absolute earliest electrogram in the targeted chamber relative to a xed
reference point such as a coronary sinus bipole (for retrograde
mapping) or a surface lead with a clearly identiable deection
(for antegrade mapping). Although tempting, it can be quite misleading to target sites with short local A-V interval (for antegrade
mapping) or V-A interval (for retrograde mapping); while this
local “fusion” is frequently present at successful sites (see
Figs.6.10, 6.11c, 6.12b, 6.13c, 6.14a, 6.15, 6.16a), it can also be
present at distant sites where both components of the local electrogram are delayed to similar degrees. Similar to mapping PVCs,
the relevance of a suspected site can be conrmed independent of
the relative timing data by analyzing precocity relative to surface
QRS onset, and local unipolar electrogram timing and morphology.
Because almost all pathways are direct AV connections crossing the mitral or tricuspid annulus, interpretation of the maps is
usually straightforward, with the earliest area being a point (or a
116
https://t.me/medicina_free
J. M. Vinocur
Fig. 6.10 Surface and intracardiac electrograms at the site of successful
ablation from mapping earliest ventricular activation in sinus rhythm, note the
very early ventricular component recorded from the ablation catheter. Artifact
in CS7,8 and ABLd channels relates to onset of RF delivery
Fig. 6.11 (a) Right atrial activation map (RAO and LAO/cranial views) of
earliest atrial activation in AVRT of the patient in Fig.6.8 with an anteroseptal
pathway. Yellow markers indicate sites where His potential was recorded;
white/pink coloration indicates the area of earliest activation; blue markers
indicate site of successful cryoablation. (b) Corresponding uoroscopy (RAO
and LAO views) of catheter positions at the successful site. (c) Electrograms
from the surface ECG, His, coronary sinus, right ventricle, and ablation catheter at the successful site
6 Wol-Parkinson-White (WPW) Syndrome
https://t.me/medicina_free
a
b
117
c
118
https://t.me/medicina_free
J. M. Vinocur
a b
Fig. 6.12 (a) Right atrial activation map (LPO and LAO views) of earliest
ventricular activation in atrial pacing of a patient with a right posteroseptal
pathway. White/pink coloration indicates the area of earliest activation. (b)
Electrograms from the surface ECG, His catheter, coronary sinus catheter,
and roving/ablation catheter at the site indicated by the green marker.
Although only 16msec prior to QRS onset, early activation was well bracketed and unipolar tip recording showed a QS morphology. Ablation at this site
eliminated the pathway within 1s
small line running across the atrioventricular groove), and with
progressively later points to either side along the annulus (see
Figs.6.11a, 6.12a, 6.13a, b). A broad area of earliest electrograms
suggests (1) imprecise electrogram interpretation that may benet
from careful manual review or switch to a different mapping strategy, (2) fusion between pathway and nodal conduction if plausible in the rhythm being used, (3) fusion between multiple
pathways, and/or (4) that the true earliest area has not been
ab
6 Wol-Parkinson-White (WPW) Syndrome
https://t.me/medicina_free
c
119
Fig. 6.13 (a) Right atrial activation map (RAO view) of earliest atrial activa-
tion during ventricular pacing of a patient with WPW and two bidirectional
accessory pathways. The right anterolateral pathway’s antegrade conduction
was weak and prone to mechanical suppression but retrograde conduction
was readily mapped after change in strategy. (b) Right atrial activation map
(LAO/caudal view) of earliest atrial activation during orthodromic AVRT in
the same patient. Antegrade conduction was not readily mapped due to complex difcult-to-annotate electrograms through a large portion of the posterior annulus, but retrograde conduction was readily mapped after change in
strategy. (c) Electrograms from the same patient. First beat, site where ablation eliminated the anterolateral pathway within 1s. Remaining beats, site
where ablation eliminated the posterior pathway within 3s
120
ab
https://t.me/medicina_free
Fig. 6.14 Surface and intracardiac electrograms (a) before and (b) just after
successful ablation performed during ventricular pacing in a patient with
WPW via a left lateral accessory pathway. Note the change from eccentric
retrograde conduction (coronary sinus activation distal to proximal) to absent
retrograde conduction exposing V-A dissociated sinus rhythm. Displayed
channels are as in Fig. 6.15
J. M. Vinocur
explored, for example on the opposite side of the atrial septum, or
(rarely) within an atrial appendage or coronary sinus.
Entrainment
Although WPW supports SVT via a reentrant mechanism, it can
be mapped like a focal tachycardia by following the activation
pattern towards the earliest site, which should correspond to
where the pathway crosses the atrioventricular groove. Thus,
entrainment maneuvers are not critical to mapping of
WPW. However, they can occasionally be useful diagnostically
(e.g. in evaluating whether an SVT is AVRT) or when there is
uncertainty about whether the pathway is left-sided or right-sided
(although usually this is evident from the retrograde atrial activa-
6 Wol-Parkinson-White (WPW) Syndrome
https://t.me/medicina_free
Fig. 6.15 Surface and intracardiac electrograms showing loss of preexcitation (between rst and second beats) due to ablation performed during atrial
pacing in a patient with WPW.Note the very early local ventricular activation
recorded from the ablation catheter on the rst beat, compared to the wellseparated atrial and ventricular electrograms on the later beats
121
tion sequencing, see Fig.6.17). When performed, the maneuvers
are comparable to those used for AVRT.
Ablation
Correct, precise mapping is the cornerstone of successful WPW
ablation. Most pathways are delicate and can be easily eliminated
with energy delivery at the correct location. However, there are
important considerations with regard to the rhythm in which
ablation is performed (see Table6.1). Because cardiac lling can
vary with heart rate and A-V relationship, the exact location of the
pathway may differ in different rhythms and therefore mapping
and ablation are ideally performed in the same rhythm.
Catheter stability can be an issue with abrupt rhythm changes
at the moment of ablation success, such as when AVRT breaks to
sinus rhythm with elimination of pathway conduction. This difculty can be minimized by mapping in AVRT and then ablating in
V-entrained AVRT. By carefully entraining just slightly faster
122
ab
https://t.me/medicina_free
J. M. Vinocur
Fig. 6.16 Surface and intracardiac electrograms (a) before and (b) just after
successful ablation performed during sinus rhythm in a patient with
WPW. Note again the very early local ventricular activation recorded from
the ablation catheter during preexcitation, compared to the well-separated
atrial and ventricular electrograms during nodal conduction. Unlike the previous gure, this patient has relatively subtle preexcitation so the changes in
surface PR interval and coronary sinus AV interval are less prominent than the
local change at the ablation site. Displayed channels are as in Fig. 6.15
than the tachycardia (often achieving sustained fusion in QRS
morphology), the map remains accurate, but at the time of pathway success there is only a small change in hemodynamics (from
fused tachycardia to fully paced tachycardia) and thus less chance
of catheter dislodgement. However, this precludes the possibility
of monitoring antegrade AV node function during ablation.
Conversely, catheter stability is less likely to be an issue when
6 Wol-Parkinson-White (WPW) Syndrome
https://t.me/medicina_free
Fig. 6.17 Orthodromic AVRT with LBBB aberrancy and earliest atrial activation at the His position, in a patient with an anteroseptal pathway
123
ablating in sinus or paced rhythm, except in the situation of V
paced rhythm with no retrograde nodal conduction, when V-A
dissociation can result in cannon A waves and intermittent sinus
capture beats. In this situation, quickly switching to simultaneous
V and A pacing can improve stability. Finally, when stability is a
persistent issue, cryoablation (with its ability to adhere to tissue)
can be helpful even if far from the normal conduction system.
Force- sensing catheters and intracardiac echo can both be helpful
in determining whether stability and contact are appropriate, particularly in challenging locations such as the right free wall.
When ablating near the AV node, antegrade properties of the
normal conduction system should be continuously monitored.
This is easy in orthodromic AVRT (see Fig.6.11c) as antegrade
conduction is exposed during both SVT and sinus rhythm after
successful termination. However, it is impossible during ventricular pacing (including V-entrained AVRT), except by alternating
between V pacing and A pacing in an attempt to monitor both
antegrade nodal and retrograde pathway conduction (a technique
124
https://t.me/medicina_free
J. M. Vinocur
that is much easier and safer with cryoablation, due to catheter
adherence and reversibility of effect). The normal conduction system can also usually be assessed during sinus or atrial paced
rhythm, as elimination of both nodal and pathway conduction
results in AV block, and elimination of nodal conduction alone
results in QRS widening (maximal preexcitation). However, when
preexcitation is maximal at baseline (due to rapid atrial pacing,
see Fig.6.1c, or when nodal conduction times are long or the pacing site is much nearer to pathway than node), it is possible to
injure the normal conduction without any outward sign.
Unfortunately, this results in a tradeoff between optimal mapping,
in which maximal preexcitation is helpful, and safest ablation,
where fused conduction is required.
Once a mapping strategy has been chosen and executed, an
appropriate site identied, and an ablation strategy selected, the
catheter is carefully positioned and energy is delivered. It is
important to anticipate which aspects of the rhythm need to be
monitored during ablation to assess effect and, potentially, AV
node conduction); usually success is obvious (see Figs.6.14 and
6.15) but occasionally it can be fairly subtle (see Fig.6.16). At an
optimal site, pathway conduction can frequently be eliminated
within a second or two of RF delivery. Ongoing ablation (beyond
5 or at most 10s) should be avoided at ineffective sites; although
“success” will sometimes be achieved late, this is often due to
partial heating from the periphery of the lesion, increasing the risk
of early recurrence either later in lesion delivery or immediately
after energy delivery is completed. Additionally, these lesions can
result in tissue edema and local electrogram fragmentation, both
of which can interfere with subsequent mapping and ablation.
Соседние файлы в папке Библиотека им академика М.И. Перельмана