From the Department of Cardiology of the University Hospital Maastricht
(J.L.R.M.S., L.-M.R., C.T., H.J.J.W.), the Netherlands, and The Bruce
Rappaport Faculty of Medicine (S.A.B.-H.), Technion-Israel Institute of
Technology, Haifa, Israel.
Correspondence to Joep L.R.M. Smeets, Department of Cardiology, University Hospital Maastricht, CARIM (Cardiovascular Research, Institute Maastricht), P. Debeyelaan 25, PO Box 5800, Maastricht, Netherlands. E-mail j.smeets{at}cardio.azm.nl
Methods and Results—Fifteen patients were studied. Accuracy
measurements were performed in 5 of them (patients 5, 6, 7, 8, and 14).
The distances between two subsequent catheter positions in the
inferior caval vein as determined by the nonfluoroscopic
mapping system were compared with measurements made with calipers by
four independent investigators using identification marks on the
catheter shaft. The difference between these two methods was
0.95±0.8 mm. In 15 patients, activation of the right atrium
and/or the right or left ventricle was recorded during sinus
rhythm. Three-dimensional activation maps were constructed in patients
with atrial and ventricular tachycardias and
Wolff-Parkinson-White syndrome.
Conclusions—With this new nonfluoroscopic mapping technique,
accurate positioning of the catheter tip is possible. A
three-dimensional activation map can be reconstructed during sinus
rhythm and during supraventricular and
ventricular tachycardias of different
compartments of the heart.
We describe a new nonfluoroscopic endocardial mapping technique using
catheters instrumented with a sensor in the distal tip to allow their
location in space using an electromagnetic field of low intensity
applied outside the body. The catheter position and orientation in
space are processed together with the intracardiac recordings.
A three-dimensional (3D) electroanatomic activation map is constructed
in real time and displayed on a graphic computer.
The purpose of this study was (1) to measure the accuracy of the
location of this catheter within the human body and (2) to report our
experience from the first 15 patients in whom this mapping method was
used.
Nonfluoroscopic Mapping System
The location pad generates a magnetic field of very low intensity (0.02
to 0.5 G). In the distal part of the steerable mapping (STAR) catheter,
a sensor is mounted. This sensor gives information about the position
(x, y, and z axes) and the rotation
(pitch, yaw, and roll) of the distal catheter
segment.11 The accuracy of the sensor position in
this low magnetic field is 0.8 mm and
5°.11
From the distal tip of the catheter, a unipolar or bipolar signal can
be recorded whose timing is related to a reference signal. In this
way, activation times are obtained in relation to the position of the
catheter in the heart.
Sequential recording of several points by dragging the catheter
along the endocardium allows a real-time construction of a 3D
activation map. An icon of the catheter is displayed together with this
3D map on the computer screen, which enables catheter manipulation in
relation to the 3D map.
A minimum of six points, three at the top and three at the lower border
of the compartment that is mapped, are needed to make a first 3D
image.
In addition to the mapping catheter, a second catheter is instrumented
with a sensor. The spatial information from this catheter is used to
detect small changes in intracardiac position due to respiration or
movement of the patient. In the computer, these small changes of the
REF catheter are used to correct the spatial information of the mapping
catheter.
Measurement Procedure
Measurements are incorporated in the 3D map when two criteria are met:
the stability criterion in space and the stability criterion in local
activation time (LAT). To check stability, two consecutive measurements
are compared. For the stability criterion, we used 4 mm; for the
LAT, 4 ms was used as a default.
The operator analyzed signals, and if the signals were accepted
as valid, they were brought into the 3D map. The 3D activation map was
updated with every accepted point.
Accuracy Assessment
Every step was measured by the CARTO system and by making an incision
with a surgical blade on the catheter shaft at the entrance of the
sheath. After the catheter had been removed from the sheet, the
distances between the markings on the catheter were measured with
calipers by four investigators and averaged. The difference between the
distances, as measured by the investigators and as measured with the
CARTO system, was calculated.
Endocardial Activation Studies
Right Atrial Activation
Sinus Rhythm
Atrial Tachycardia
Activation of the Left Atrium
Activation of the Right Ventricle
Activation of the Left Ventricle
Patient 1 suffered from an anteroseptal myocardial infarction 4 years
before the present study. Ventricular
tachycardias that were hemodynamically well
tolerated were recorded for the first time 2 years after myocardial
infarction. Recurrent episodes of ventricular
tachycardia occurred in spite of antiarrhythmic drug
treatment.
The 12-lead ECGs obtained during sinus rhythm and
ventricular tachycardia are shown in Figure 5
The endocardial activation sequence of the left ventricle during
ventricular tachycardia is illustrated in
Figure 6
During sinus rhythm (Figure 7
Complications
In another patient (patient 5), right atrial and
ventricular activations were mapped. The patient was
heparinized. Subsequently, a standard RF catheter ablation of the slow
AV nodal pathway was performed for AV nodal reentrant
tachycardias. At the end of the procedure, the patient
complained of chest pain on movement and inspiration, suggesting a
pericardial origin. In the next 48 hours, progressive pericardial
effusion developed that required drainage. Sanguinolent fluid (150 mL)
was removed, suggesting a perforation. The perforation site (in the
right atrium or right ventricle) was not identified. The patient
recovered uneventfully.
The CARTO system, together with the STAR catheter, gives us the
opportunity to create an accurate geometric representation of
the endocardial electrophysiological
recordings. Although it does not allow direct recognition of
anatomic structures (such as the terminal crest or papillary muscles),
the CARTO system, using endocardial recordings, allows an
accurate geometric reconstruction. The CARTO system can be of help in
positioning of the catheter, especially when the normal anatomy
has been changed, as in myocardial infarction or corrected congenital
heart disease. The effect of maneuvering the catheter can be evaluated
(owing to the icon that represents the catheter tip) in
relation to the electroanatomic map.
Before this system can be routinely used in the diagnosis and treatment
of different arrhythmias in humans, the accuracy of the
positioning of the distal segment of the catheter should be known. For
this reason, we performed five ruler experiments. The purpose was to
measure what the overall accuracy would be when this system was applied
in the human situation. In bench testing as well as in animal testing,
accuracy was very high (0.25 and 0.3 mm,
respectively).11 The accuracy of positioning the
catheter within the inferior caval vein, during which time
the catheters are located within a sheath, was <1 mm. The
following possible sources of error are included in this assessment:
(1) system error (as in bench testing), (2) movement of the sheath
within the bloodstream, (3) slippage of the catheter in the rubber
stopcock in the sheath, and (4) reading errors by the investigators
using the calipers. Despite these possible sources of error, accuracy
is very high, especially in relation to the size (4 mm) of the tip
of a standard RF ablation catheter. For obvious reasons, these
measurements were made in the inferior caval vein. It is
possible that accuracy in catheter location is not the same in a
beating, non-tubelike environment such as the cardiac chambers.
We were able to reconstruct 3D electroanatomic maps during sinus rhythm
as well as during different arrhythmias such as atrial and
ventricular tachycardias. In sinus rhythm, the
right atrium and proximal part of the coronary sinus are
activated within 83.7 ms and the left atrium in 72 ms. This is
in agreement with studies in the explanted human
heart.19 Activation of the atria is sequential
and relatively slow because in the atria, no specific conduction tissue
is present. In contrast, the right as well as the left
ventricular endocardium is activated within 45 ms
owing to the presence of the intraventricular
conduction system. Similar observations have been made using
single-catheter mapping.20 Only endocardial
ventricular activation can be measured, and therefore
transmural conduction toward the epicardium cannot be recorded with
this system.
A 3D map of an atrial tachycardia showed that activation of
the atrium during tachycardia started
An advantage of this new system is the representation of the
actual catheter position within the 3D map during acquisition of the
data. The effect of movement of the tip of the catheter can be
evaluated immediately in relation to the 3D map. Directing the catheter
to a specific site will be easier and more reproducible. This may
facilitate catheter handling and may shorten procedure time. Because
catheter handling is largely done without fluoroscopy, x-ray exposure
for both patient and investigator should diminish considerably.
However, randomized studies to compare fluoroscopy exposure with and
without use of the CARTO system must be performed.
Dr Ben-Haim is founder and director of Biosense Corporation, which manufactured the CARTO system and developed the concepts used in this study.
Received May 29, 1997;
revision received February 3, 1998;
accepted February 13, 1998.
© 1998 American Heart Association, Inc.
Clinical Investigation and Reports
New Method for Nonfluoroscopic Endocardial Mapping in Humans
Accuracy Assessment and First Clinical Results
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Background—Accurate mapping of the
site of origin and activation sequence of a cardiac arrhythmia
is essential for a successful catheter ablation procedure. To achieve
this, precise and reproducible catheter manipulation is mandatory. The
aim of this study was (1) to assess the accuracy of a new
nonfluoroscopic mapping system in humans and (2) to report the first
result of endocardial activation mapping with this system during sinus
rhythm and several types of supraventricular and
ventricular tachycardias.
Key Words: mapping • arrhythmia • ablation
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
Accurate mapping of
the site of origin or activation sequence of a cardiac
arrhythmia is essential for a successful radiofrequency (RF)
catheter ablation procedure. With the use of different kinds of plaque
and sock arrays, high-resolution epicardial and endocardial activation
maps of arrhythmias have been made during open heart surgery in
patients with Wolff-Parkinson-White syndrome,1
ventricular tachycardias after myocardial
infarction,2 3 4 5 atrial
tachycardia,6 7 and atrial
fibrillation.8 In the intact heart, endocardial
catheter mapping of an arrhythmia is difficult because only a
limited number of intracardiac electrodes can be introduced, allowing
simultaneous activation mapping from only a few
sites.9 During endocardial catheter mapping, the
relation between the intracardiac recording and the
anatomy of the heart is made by the investigator using
bidirectional fluoroscopy. Positioning of the catheter with the use of
fluoroscopy can be time consuming and is often poorly reproducible. For
this reason, several types of multipolar catheters (eg, basket) are now
being developed to make mapping more accurate and
faster.10
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
This study was performed in 15 patients (Table 1
) who were admitted for
electrophysiological evaluation and
subsequent catheter ablation of their arrhythmia. All
antiarrhythmic medication was stopped at least five half-lives before
the investigation. No patient was taking amiodarone.
View this table:
[in a new window]
Table 1. Sex, Age, Type of Arrhythmia, and Site of
Endocardial Map(s) in the 15 Patients
Studied
The system has recently been described in
detail.11 In short, the nonfluoroscopic mapping
system (CARTO) consists of a location pad positioned under the bed of
the patient, two catheters instrumented with a sensor and reference
(REF) catheter, a mapping system, and a graphic computer (Silicon
Graphics).
The mapping and reference catheters are positioned in the heart
under fluoroscopic guidance. The reference electrode is preferentially
positioned contralateral to the compartment that is being mapped. This
reduces the risk of dislodging the position of the reference catheter
because of manipulation of the mapping catheter. After six points are
acquired with the mapping catheter by use of fluoroscopy, a 3D map is
generated. Further catheter handling can now be guided by the 3D image
in which the icon is displayed. Fluoroscopy is only needed if the
mapping catheter slips outside the compartment that is being
mapped.
In five patients, two 9F sheaths (60 cm long) were advanced
under fluoroscopic guidance from the left and right femoral veins into
the inferior caval vein just below the right atrium. The
sheaths were positioned outside the heart to avoid movement by
contraction of the heart. The reference catheter was positioned in the
distal part of one sheath so that the tip of the catheter was within
the sheath. The mapping catheter was positioned in the other sheath at
the same level. This catheter was withdrawn in the direction of the
femoral vein in 14 to 19 steps.
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
Accuracy Assessment
As discussed in the "Methods" section, the mapping electrode
in five patients was withdrawn 14 to 19 times (average, 16±1.9) per
experiment over a distance of 141.4±30.6 mm (range, 101.8 to
184.9 mm). Per step, the distance was 5.5 to 14.9 mm
(average, 8.73±1.61 mm; median, 8.8 mm) and 6.1 to 17.7
mm (average, 9.7±1.8 mm; median, 10.2 mm), as measured with
the CARTO system and calipers, respectively, by four independent
investigators. The difference between the distance as measured with the
CARTO system and the averaged catheter incision values was
0.95±0.8 mm (median, 0.86 mm).
In Table 2, information is given
about the number of points that were serially collected to construct a
3D map. In 27 maps, 50 to 170 points were recorded (mean,
88.9±29.7). It took 35.7±17.8 minutes to collect those points. In
patient 12, it took 97 minutes to record 170 points. It took so
long in this patient because the ventricular
tachycardia stopped frequently owing to catheter
manipulation and had to be reinitiated. The definite map, after
editing, was composed of 74.7±26.6 points. The main reason points were
skipped was a marginal stability in space, LAT, or both. The majority
of points were collected manually (not in the semiautomatic mode).
View this table:
[in a new window]
Table 2. Number of Points for Three-dimensional Map (Before
and After Editing) and Time Needed to Construct
Map
During construction of maps of the atrium, the REF catheter was
positioned in the coronary sinus.
Figure 1 shows the activation
sequence of the right atrium during sinus rhythm. The activation
sequence is color coded, starting with red and going to purple. The
anatomic orientation points are the superior caval vein,
coronary sinus, inferior caval vein, and tricuspid
valve. In the right atrium, the earliest endocardially
activated area is the transition of superior caval vein to the
right atrium. This represents the activation of atrial muscle
at the exit site of the sinus node (Figure 1, Top). Activation then
proceeds in a posterior direction where anatomically the crista
terminalis is situated, and spreads over the entire atrium (Figure 1, Bottom). In the 10 patients in whom right atrial endocardial activation
maps were recorded, the total right atrial activation time from the
sinus node exit to the AV ring and coronary sinus os ranged
from 64 to 110 ms (mean, 83.7±14.7 ms).
View larger version (75K):
[in a new window]
Figure 1. Activation map of the right atrium (RA) during
sinus rhythm. Top, Right anterior oblique view shows in red the
earliest area of endocardial activation, located at the anterior
entrance of the superior caval vein into the right atrium. The sinus
node region is located in this area. Activation proceeds toward the
lateral wall and inferior caval vein and posterolateral
along the crista terminalis in the direction of the tricuspid valve
(bottom, right posterior view).
Figure 2 (top) shows an activation
map of the right atrium during atrial tachycardia. In
contrast to the activation sequence during sinus rhythm, the earliest
activated site (red area) is in the anterolateral part of the
right atrium 1.5 cm above the tricuspid valve. Activation then spreads
radially in a superior and posterior direction opposite to the normal
activation sequence during sinus rhythm. During this atrial
arrhythmia, endocardial activation of the right atrium was
completed in 92 ms. Endocardial activation during sinus rhythm, after
successful RF ablation of the atrial tachycardia, is shown
in Figure 2, bottom.
View larger version (76K):
[in a new window]
Figure 2. Endocardial activation map during atrial
tachycardia. The right atrium is shown in a left anterior
oblique view. The superior part represents the superior caval
vein, the lateral part indicates the coronary sinus, and the
opening represents the tricuspid valve. Note that the
anterolateral part of the right atrium (RA) is activated first,
as indicated by the red color. Activation then proceeds to the
posterior and superior parts of the right atrium (top). Bottom, The
activation sequence is shown after successful RF ablation of the right
atrial focus. During sinus rhythm, first activation (red area) is found
as expected in the transition area between superior caval vein and
right atrium. LA indicates left atrium.
During sinus rhythm, a mapping catheter was advanced transseptally
into the left atrium (Figure 3). Earliest
activation of the left atrium was recorded anterior from the
septum, where anatomically the bundle of Bachmann is located (the red
area). Activation then proceeds radially in the direction of the mitral
valve. The last part to be activated is the lateral wall of the
left atrium.
View larger version (148K):
[in a new window]
Figure 3. Right anterolateral view of the left atrium
showing the activation sequence during sinus rhythm. Earliest
activation starts in the anterior part of the left atrium,
corresponding to the site of insertion of Bachmann's bundle.
Activation spreads evenly in the anterior and superior direction. Total
left atrial endocardial activation time is 70 ms.
The activation sequence of the right ventricle during sinus rhythm
is shown in Figure 4. Note that in
contrast to the map of the right atrium during sinus rhythm, several
areas are activated early, as indicated by the red and yellow
areas. One red area is located 
1 cm distal to the site where the His
bundle potential could be recorded. A second early-activation area
is in the low inferoseptal area. This could represent the area
where the right bundle activates the right
ventricular endocardium. The part of the right ventricle
last activated is the inferior and posterobasal
area. In the seven patients in whom this was recorded, total
activation of the endocardium of the right ventricle during sinus
rhythm was completed within 37 to 52 ms (mean, 45.1±10.1 ms).
View larger version (144K):
[in a new window]
Figure 4. Activation of the right ventricle during sinus
rhythm in a right anterior oblique view. Early activation (red area) is
found in the basal region of the septum. The anterior wall and apex are
activated nearly simultaneously, as indicated by
the yellow color. The posterobasal and inferior part is
activated last, as indicated by the purple color. Note that
endocardial activation of the right ventricle is completed within 38
ms.
During mapping of the left ventricle, the reference catheter was
positioned in the right ventricular apex. This was done to
ensure correct and simultaneous movement with the roving
ventricular electrode even if AV dissociation was
present during ventricular tachycardia. . Analysis of the wide QRS
tachycardia suggests a location of the
tachycardia in the inferoseptal
region.12
View larger version (93K):
[in a new window]
Figure 5. Left side shows a wide QRS tachycardia
at a rate of 120 bpm. The QRS complex has a width of 160 ms, shows a
left axis, and has a right bundle-branch block shape with qR complexes
in leads V1 and V2. ECG during sinus rhythm
shows an old anteroseptal myocardial infarction. There are
respiration-induced QRS changes during sinus rhythm. . The map consists of 72
sequential points. Earliest endocardial activity was located in the
infero-apico-septal region at the base of the papillary muscle.
Endocardial activation then proceeded toward the lateral wall. Total
activation time of the endocardium of the left ventricle during
ventricular tachycardia was 69 ms. Parts of the
ventricle (especially anterior and basal) were not mapped. The
explanation for this incomplete map was twofold: (1) this was the first
patient in whom we made an electroanatomic activation map, and (2) the
first-generation catheter was relatively stiff at the tip, limiting
maneuverability in some parts of the ventricle.
View larger version (151K):
[in a new window]
Figure 6. Right anterolateral view of activation of the left
ventricle during ventricular tachycardia. Site
of earliest activation is at the septal endocardial surface.
Thereafter, activation proceeds along the anterolateral wall. The last
part of the left ventricle to be activated is the basolateral
wall (total activation time of 77 ms). Note that whereas it takes 160
ms to activate both ventricles, left ventricular
endocardial activation is completed within 80 ms. ), the
earliest activation was found in high anterolateral and
mid-inferoseptal locations. The two early-activated areas were
sites where anatomically the anterior and posterior fascicles are
situated. The apical part of the left ventricle could not be mapped in
detail during sinus rhythm.
View larger version (80K):
[in a new window]
Figure 7. Same patient as in Figure 6 
. Activation sequence
of the left ventricle during sinus rhythm in a left anterolateral (top)
and right lateral (bottom) view. Earliest endocardial activation of the
left ventricle is seen in the inferoseptal (bottom) and anterolateral
part (top), corresponding to the position of the posterior and anterior
fascicles of the conduction system. The apical part of the left
ventricle was not mapped during sinus rhythm.
The STAR (type F-curve, first version) catheter has a rigid
segment due to implementation of the sensor into the distal part of the
catheter. This limits steerability and maneuverability. When we tried
to map the ventricle, problems occurred in two patients. In patient 8,
the ascending aorta was narrow compared with the long, stiff, distal
segment of the catheter, preventing retrograde passage of the aortic
valve, and the procedure was stopped.
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
Since the introduction of RF catheter ablation as a therapeutic
modality, many arrhythmias can be cured. In particular,
arrhythmias associated with Wolff-Parkinson-White syndrome, AV
nodal reentrant tachycardia, and ventricular
tachycardias in a structurally normal heart have been
successfully treated with this technique.13 14 15 16 17 18
Less satisfactory results are obtained in arrhythmias arising
in hearts with altered anatomy, as in ventricular
tachycardia after myocardial infarction. Under those
circumstances, catheter maneuvering guided by bidirectional fluoroscopy
can be difficult and time consuming and is poorly reproducible. This
may play a role in the lower success rate of catheter ablation in
ventricular tachycardia after myocardial
infarction. 1.5 cm above the
tricuspid valve. The site of origin of this arrhythmia could be
well localized with this new mapping system. RF application terminated
the atrial tachycardia abruptly. Although the mechanism of
the arrhythmia cannot be proved with this mapping system,
insight can be given in the role of anatomic structures, such as old
myocardial infarction and surgical scar, in relation to
arrhythmogenesis. In ventricular tachycardia
after myocardial infarction, reentry is the arrhythmogenic
mechanism.21 Interpretation of an early
endocardial breakthrough like the one shown in the map of Figure 7 is
difficult. It may be early endocardial activation over a bystander
pathway, whereas the reentry circuit is located intramurally or even
epicardially. Further studies must be performed to develop criteria
using this new tool to identify appropriate endocardial sites to which
RF energy should be applied to terminate the ventricular
arrhythmia. At this time, stimulation techniques need to be
performed to identify whether the earliest site of endocardial
activation is indeed incorporated in the
circuit.22
Footnotes
Guest editor for this article was Mark E. Josephson, MD, Beth Israel Hospital, Boston, Mass.
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
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S. Y. Ho and R. H Anderson Invited Commentary Asian Cardiovasc Thorac Ann, December 1, 1999; 7(4): 349 - 352. [Full Text] [PDF]
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F. X. Roithinger, J. Cheng, A. SippensGroenewegen, R. J. Lee, L. A. Saxon, M. M. Scheinman, and M. D. Lesh Use of Electroanatomic Mapping to Delineate Transseptal Atrial Conduction in Humans Circulation, October 26, 1999; 100(17): 1791 - 1797. [Abstract] [Full Text] [PDF]
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D. J. Callans, J.-F. Ren, J. Michele, F. E. Marchlinski, and S. M. Dillon Electroanatomic Left Ventricular Mapping in the Porcine Model of Healed Anterior Myocardial Infarction : Correlation With Intracardiac Echocardiography and Pathological Analysis Circulation, October 19, 1999; 100(16): 1744 - 1750. [Abstract] [Full Text] [PDF]
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C. Pappone, G. Oreto, F. Lamberti, G. Vicedomini, M. L. Loricchio, S. Shpun, M. Rillo, M. P. Calabro, A. Conversano, S. A. Ben-Haim, et al. Catheter Ablation of Paroxysmal Atrial Fibrillation Using a 3D Mapping System Circulation, September 14, 1999; 100(11): 1203 - 1208. [Abstract] [Full Text] [PDF]
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H. Sun, E. O. Velipasaoglu, D. E. Wu, H. A. Kopelen, W. A. Zoghbi, W. H. Spencer III, and D. S. Khoury Simultaneous Multisite Mapping of the Right and the Left Atrial Septum in the Canine Intact Beating Heart Circulation, July 20, 1999; 100(3): 312 - 319. [Abstract] [Full Text] [PDF]
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