Progress in Catheter Ablation: Clinical Application of New Mapping and Ablation Technology

590 Pages·2001·2.49 MB·English

by  Ruben Coronel

218 Progress ni Catheter Ablation
monofocal origin of each beat ni the left ventricular apex at C .2-1 The bipolar
electrogram from these electrodes showed just a small presystolic potential
preceding the surface ECG signals by merely 20 .sm The subsequent spread of
activation from the earliest site was then radial with no indication of a macro›
reentrant return path. The underlying mechanism of the tachycardia was either
micro-entrant or abnormal automaticity. Exploration with na ablation catheter
confirmed that presence of a small pre-potential. Radiofrequency ablation of that
site resulted ni the inability ot reinduce the ventricular tachycardia. No clinical
recurrences or discharges of the patient’s defibrillator have occurred ni three
years of follow-up.
2.4 PATIENT #4
This 50-year-old woman had a surgical repair of an atrial septal defect at the
age of .21 Postoperatively the patient remained asymptomatic until age 26 when
she began to complain of increasingly frequent episodes of sudden onset irregular
palpitations lasting hours or days. During thcsc attacks the ventricular rate was
l30/min. Amiodarone and sotalol produced unacceptable side effects. ECG
documentation revealed an atrial flutter of atypical morphology. On the
presumption that the patient may have had an incisional atrial reentrant
tachycardia caused by either repair of her ASD or around the• site of her atrial
cannulation, basket catheter mapping of the right atrium was performed.
Figure 31 shows the fluoroscopic image of the basket catheter in position ni
the right atrium ni a (cid:176)03 right anterior oblique projection.
Figure 41 shows na isochronal map of her right atrial activation ni the upper
panel. Key local bipolar atrial electro grams are shown ni the lower panel.
During the atrial tachycardia earliest atrial activation occurred at the base of
spline D at D7-8. Activation then progressed counterclockwise around the base
of the right atrium and upwards along D ot reach sti tip at D 2-1 by 60 ms. From
there activation crossed over to the tip of the closely neighboring electrode E 2-1
and down strut E reaching its base at E 7-8 by 001 .sm The electrograms from D
and E clearly show this ni their sequential activation seen ni the lower panel.
This activation sequence si consistent with a conduction block between struts D
and ,E which anatomically corresponded to the lateral eerf wall of the right
atrium. At the base of E at E 7-8, there are double potcntials, the diminished
second component of which (indicated by arrowheads) gives rise ot a fully
developed electrogram on closely neighboring D 7-8, setting off the next cycle
D( 8-7 si shown at the top and bottom of the electrogram panel ot facilitate
orientation). nI the entire circuit of activation, the greatest delay of conduction
59( ms) occurs at a single location on E 7-8, suggesting this was the critical
portion of the return path. Although functional tests for concealed entrainment
were not performed, application of RF energy at this site resulted ni termination
Chapter 14 Mapping Using Basket Catheter 219
of the atrial tachycardia within five seconds. The patient has remained free of
clinical recurrences over the follow-up period of one year.
Figure .31 Fluoroscopic image of basket catheter in the right atrium in a 30(cid:176) right ant e rior oblique
projection of patient #4. See et x .t
022 Progress ni Catheter Ablation
A
\
c
G
D
.’
E
07-8
06-7
05-S
04 -5
03-4
02 -3
01-2
E1-2
E2-3
E3-4
E4-5
S-5E
SE -7
7E -8
07-8
II
500 sm
Figure .41 Upper panel: Right atrial activation during cht atrial tachycardia ofpaticnt #4 shown ni
lower panel. Lower panel shows selected bipolar atrial electrograms and surface lead II during
atrial tachycardia. Red arrowheads indicate second component of double potentials seen no E7-8.
These immediately preceeded start of next atrial cycle which started no .8-7D See .txet
Chapter 14 Mapping Using Basket Catheter 221
3. RESULTS
The cases presented ni the foregoing are clearly not comprehensive but rather
serve to illustrate the utility of basket mapping. The detail of underlying
arrhythmia mechanisms can sometimes be revealed in astonishing detail, which
may be critical ot the successful outcome of an ablation attempt. As already
discussed care has to be taken ot ensure that the basket si appropriate ni both size
and sti placement ni the correct cardiac chamber. Before placement it si
advisable ot first check that the clinical arrhythmia si inducible. Our total
experience includes 61 patients with ventricular tachycardia ni which II
underwent left ventricular mapping and 5 right ventricular mapping. The
mapping contributed to a successful ablation ni twclve patients. nI four patients
(two right ventricular and two left ventricular) ablation was unsuccessful. Failure
was attributed ot the target tissue being ni deeply intramural or epicardial ni 3
patients and ot a broadly diffuse return path with multiple exits ni one patient.
Thirteen atrial arrhythmias were mapped with a basket catheter - eleven ni the
right atrium and two ni the left atrium. Ablation of these arrhythmias was
successful ni eight of the right atrial cases. nI the two patients with left atrial
mapping the clinical atrial arrhythmia switched ot a right atrial flutter which
preempted evocation of the left atrial arrhythmia. Throughout the entire
experience there were no complications attributable ot the basket catheter. One
patient had a cerebro-vascular accident from a left ventricular mural thrombus
that was dislodged by manipulation of the ablation catheter. That patient had
undergone na extensive left ventricular ablation one week earlier at the referring
hospital and had not been covered by anticoagulants ni the intervening week.
After that experience, ti has been our practice ot try and avoid performing left
ventricular ablation within a month of a previously failed ablation attempt.
CONCLUSION
Basket catheter mapping has proved ot be effective ni guiding and achieving
successful catheter ablation in cases where conventional mapping has failed or si
unlikely ot succeed by virtue of the nature of the arrhythmia or sti hemodynamic
consequences. Refractory ventricular tachycardias and supraventricular
arrhythmias, particularly atrial tachycardia resulting from prior atriotomies
should eb considered for basket mapping.
In comparing basket mapping with alternative new mapping techniques such
sa the non-contact method, both advantages and limitations are apparent and
should be taken into consideration before deciding on one technique. These are
itemized ni Table .4 Electroanatomie mapping techniques are restricted ni their
applicability to arrhythmias that are electrically and hemodynamically stable
because they depend on sequentially collected data.
222 Progress ni Catheter Ablation
These very different new techniques should not be viewed sa competing
alternatives but rather as different tools ot be chosen from ot best address the
challenge of a particular arrhythmia. Future developments of the basket catheter
are likely to include an asymmetric electrode distribution to improve spatial
resolution ni a region of interest. Combination of the basket with intracardiac
echocardiography also promises high resolution true electrode-anatomic mapping
on a beat-by-beat basis. Utilization of actual electrograms from the basket
electrode to compute virtual electro grams ni the intervening space, theoretically
could also greatly enhance the electrical resolution of basket mapping.
TABLE .4 Comparison of Basket with Non-Contact Mapping Systems
Basket Non-Contact
- Spatial resolution limited to 64 electrodes. - Extremely high resolution> 3000 virtual
electrograms.
- Contact or close proximity necessary. - Contact unnecessary.
- Geometry of arra y restricted yb basket. - Geometric shell complies closely with
anatomy.
- Electrograms are real and without distorsion. - Virtual electrograms are computed - Despite
good correlation with real electro grams some
distorsions occur.
- Electrograms seen are at the anatomic position ofthe - Electrograms are projected onto endocardial
electrodes and are derived from electrically surface and assigned ot that specific site even
excitable myocardium at that site. ifthere is no electrically excitable
myocardium there e.g. dacron patch. This
may lead to misdirected ablation attempts.
- Movement of basket does not invalidate mapping - Movement of mapping balloon may
since basket array is self-referencing. invalidate spatial construct of mapping.
- Although interpretation may be complex, it is - Requires separate dedicated console rof
usually feasible using standard recording systems. display and analysis which may eb complex.
- Provided basket is sized appropriately even the - Comparatively "near-sighted": beyond 3 cm
largest cardiac chambers can be encompassed. may miss critically vital real electrograms.
REFERENCES
I. Downar E, Parson ,Dr Yao ,L Cameron DA and Waxman MB: Endocardial Catheter Mapping
of Unstable and Pleomorphic Ventricular Tachycardias, Circulation 1984;70(Supp :)II .8841
.2 Browne ,FK Chilson DA, Waller BF and Zipes :PD esU of a Spatially Distributed
Multielectrode Catheter ot Activation Map the Left Ventricular Endocardium Simultaneously
and Destroy Selected Areas, Circulation I 983;68(Supp III):84.
.3 Jenkins KJ, Walsh ,PE Colan ,DS Bergau DM, Saul jp and Lock :EJ Multipolar Endocardial
Mapping of the Right Atrium During Cardiac Catheterization: Description of a New
Technique, J Am Coil cardioI1993;22:II05.
.4 Eldar ,M Fitzpatrick AP, Ohad ,D Smith MF, Hsu ,S Whayne JG, Vercd ,Z Rotstcin ,Z Kordis
T, Swanson DK, Chin ,M Scheinman MM, Lesh MD and Greenspon :JA Percutaneous
Multielectrode Endocardial Mapping During Ventricular Tachycardia in the Swine Model,
Circulation 1996;94: .5211
Chapter 14 Mapping Using Basket Catheter 223
.5 Downar ,E Kimber ,S Harris ,L Mickleborough ,L Sevaptsidis ,E Masse ,S Chen TCK and
Genga :A Endocardial Mapping of Ventricular Tachycardia in the Intact Human Heart .II
Evidence for Multiuse Reentry in a Functional Sheet of Surviving Myocardium, J Am Coll
Cardiol 1992;20:869.
.6 Downar ,E Saito ,J Doig JC, Chen TCK, Sevaptsidis ,E Masse ,S Kimber ,S Mickleborough L
and Harris L: Endocardial Mapping of Ventricular Tachycardia in the Intact Human Ventricle
.III Evidence of Multiuse Reentry With Spontaneous and Induced Block ni Portions of
Reentrant Path Complex, J Am Coll CardioI1995;25: 1591.
retpahC 51
ENDOCARDIAL GLOBAL NONCONTACT MAPPING
(ENSITETM)
Bradley .P Knight, Fred Morady
Department of Internal Medicine, Division of Cardiology, University of Michigan Medical
center. Ann Arbor. Michigan. ASU
INTRODUCTION
Multisite epicardial activation mapping sah advanced our understanding of
arrhythmia mechanisms and has served sa a valuable tool during arrhythmia
surgery. Conventional endocardial mapping during percutaneous radiofrequency
ablation procedures generally si performed using 3-1 catheters, each with a
limited number of electrodes. In ,tcaf some arrhythmias, such sa V A nodal
reentrant tachycardia, can be diagnosed and cured with radiofrequency ablation
using only two quadrapolar catheters. However, current catheter-based mapping
techniques have significant limitations when attempts are made to ablate complex
arrhythmias, such sa ventricular tachycardia ni patients with a history of
myocardial infarction.
Noncontact mapping has been developed to permit high-resolution global
activation mapping of the endocardium without the need for endocardial
contact.’•2 The technique si based on the ability to compute far-field endocardial
electrograms from analysis of intracavitary potentials. This chapter reviews the
commercially available Ensite 3000 noncontact mapping system developed by
Endocardial Solutions, Inc. .tS( Paul, MN) and describes sti use during ablation
of cardiac arrhythmias. Because thc valuc of thc mapping system si hcavily
dependent on the accuracy of the virtual electro grams and locator signal, a
detailed review of published validation studies si also included.
522
.L Bing Liem and .E Downar .).sde( Progress ni Catheter Ahlation, 225-240.
' 200 I Kluwer Academic Publishers.
226 Progress ni Catheter Ablation
.1 DESCRIPTION OF EN SITE 3000(cid:153) NONCONTACT
MAPPING SYSTEM
The Ensite 3000(cid:153) noncontact mapping system derives information from
two sources - a multielectrode array (MEA) and a catheter locator signal. Data
from these two sources are used ot construct a high-resolution, three-dimensional
graphical representation of endocardial activation using dynamic isochronal or
isopotential color maps.
1.1 Multielectrode Array (MEA)
The MEA si designed ot record cavitary potentials. The array si a mesh of
0.003-inch diameter polyimide-coated stainless steel wire that covers na
inflatable 7.5-ml balloon (Figure I). Sixty-four electrodes are created by
removing a small amount of the insulation from the wires at specific locations.
The MEA si mounted on a 9 -French lumenal pigtail catheter that can be
advanced percutaneously into any cardiac chamber over a 0.035 guidewire. Ring
electrodes are positioned on the catheter with one distal and three proximal ot the
balloon.
Figure .I The multielectrode array catheter. The 9 French pigtail catheter si shown with eht balloon
deflated and the protective sheath that has been advanced near eht end of eht catheter (Left). The
wire mesh of O.0003-inch diameter polyimide-coated stainless steel si visible on the surface of the
inflated balloon (Middle). A photomicrograph si shown of one of eht electrodes that are created by
removing the insulation with a laser (Right).
Chapter 15 Noncontact Mapping Using EnSite 227
2.1 Locator Signal
The tip of any standard electrode catheter can be located relative to the MEA
by use of the locator signal. A 5.68-kHz signal si emitted from the distal
electrode and is detected by the electrodes on the MEA. The location of the
mapping catheter is updated 001 times per second on the display. The locator
signal is used to define the geometry of the endocardial border and ot pinpoint
the position of the mapping/ablation catheter.
3.1 Determination of Chamber Geometry
After the MEA and mapping catheters are positioned in the heart, the chamber
geometry si determined. This permits construction of a three-dimensional model
of the endocardium on which the activation maps are displayed. Accurate
identification of the endocardial border as a reference si critical ot the accuracy
of the activation maps. The roving contact catheter si systematically moved
within the cardiac chamber to identify sa much of the endocardial border as
possible. The endocardial display si continuously updated sa more distant sites
are reached ot construct a multifaceted model. A smoothing process is applied ot
create a more realistic endocardial model (Figure .)2 This process takes
approximately 5 minutes to complete.
Figure .2 A three-dimensional model of the endocardium si constructed on which eht activation
maps are displayed. A multifaceted model si continuously updated during sti creation, sa more
distant sites are reached with the roving catheter (Left). A smoothing proccss si applied ot makc a
more realistic endocardial model (Right).
4.1 Generation and Display of Activation Maps
Low-amplitude, low-frequency, far-field cavitary signals era sampled at 1200
times per second from the 46 noncontact balloon electrodes. A custom-designed
amplifier si used and the potentials are filtered with a programmable bandwidth
between 1.0 and 300 Hz. The data si processed using a Silicon Graphics
228 Progress ni Catheter Ablation
workstation with custom software. A boundary-element method based on an
inverse solution to Laplace’s equation si used ot compute 3,360 unipolar
endocardial clectrograms from the cavitary potentials. Sophisticated algorithms
I
are also applied to the data ot minimize noise.
Isopotential or isochronal activation maps are displayed on a computer screen
(Figure .)3 A color range si used to define the voltage or the timing of onset.
The three-dimensional image of the heart chamber can be "cut away" and
interactively rotated using a mouse, to allow visualization from different angles
(Figurc .)4 The position of thc tip of the roving catheter si continuously
displayed on the virtual endocardial model. Local virtual electrograms can also
be selected using a cursor and displayed sa waveforms along with the contact
catheter and surface electrograms (Figure .)5
Figure .3 Shown si the Ensite 3000(cid:153) System and display with the multi electrode catheter ni the
foreground.
.2 ENSITE SYSTEM NOITADILAV
1.2 Validation of the Locator Signal
A validation study of the locator signal was performed using a saline-filled
tank to simulate intracardiac noncontact mapping. 2 Using this model, the
precision of the locator signal was found to be 0.33–0.45 mm at distances of <50
mm from the MEA balloon and 0.75–1.13 mm at distances of >50 mm. The