From the Division of Cardiology, Hospital of Asti (F.G., R.R., L.C.,
M.S., L.G., F.L., E.R.); the Department of Physics, University of Trento
(R.A.); and CMBM (R.A., M.K.), Trento, Italy.
Correspondence to Fiorenzo Gaita, MD, Division of Cardiology, Hospital of Asti, Via Botallo 4, 14100 Asti, Italy. E-mail cardclin{at}provincia.asti.it
Methods and Results—Sixteen patients with idiopathic AF underwent
atrial mapping during AF and then RF ablation in the right atrium. The
atrial activation was simultaneously recorded in four
regions in the right atrium: high lateral wall (HL), low lateral wall
(LL), high septum (HS), and low septum (LS) and in the left atrium
through the coronary sinus (CS). In these regions, we evaluated
the atrial fibrillation intervals (FF) and the morphological features
of AF recordings by Wells' classification. No complications
occurred during RF ablation. Of the 16 patients, 9 (56%) without AF
recurrences during the follow-up (11±4 months) were considered
successfully ablated. These patients showed a significantly shorter
mean FF interval in the HS and the LS (122±32 and 126±28 ms,
respectively) than in the HL and LL (159±24 and 156±28 ms,
respectively). Moreover, the septum had more irregular electrical
activity with greater beat-to-beat changes in FF and a higher
prevalence of type III AF than the lateral region. The CS had similar
behavior to the septum. Conversely, patients with unsuccessful ablation
had an irregular atrial activity in the lateral wall, septum, and CS
with no significant differences between the different sites.
Conclusions—Right atrial endocardial catheter ablation of AF is a
safe procedure and may be effective in some patients with idiopathic
AF. The atrial mapping during AF showed a more disorganized right
atrial activation in the septum than in the lateral wall in patients
with successful ablation.
The aim of this work was to evaluate in patients with idiopathic AF (1)
the electrophysiological features of atrial
activation, (2) the possibility of restoring sinus rhythm and
preventing recurrences of AF with RF catheter ablation
performed only in the right atrium, (3) the safety of this procedure,
and (4) the relationship between the results of catheter ablation and
atrial mapping. Because the ablation procedure was limited to the right
atrium to avoid the risk of thromboembolism, we selected patients with
idiopathic AF and, among these patients, those in whom the
arrhythmia seemed to be induced by a vagal trigger because in
these patients the right atrium might be more directly involved in AF
initiation and perpetuation.12 13 14
Electrophysiological Study
Electrophysiological Parameters
Two different types of analysis were performed. First, AF
intervals (FF) were simultaneously measured in the
different sites for the same period of 10 seconds (epoch a). Forty
seconds after the end of this interval, a second period of 10 seconds
was selected, and the measurements were repeated to assess the
reliability of the results in different moments of AF (epoch b). The
measurements were performed manually on the Cardiolab system at a
screen speed of 200 mm/s by use of on-screen calipers, and the FF
intervals were measured as described by Kalman et
al.17 We considered as different F waves the
presence of two distinct electrograms clearly separated by an
isoelectric space of at least 50 ms. The choice of the limit of 50 ms
for the shortest FF interval, which is similar to that used in other
studies,18 and the simultaneous
evaluation of the atrial electrograms in the sites adjacent to those
analyzed were aimed to reduce the interference of double or
fragmented and long-duration electrograms. Both the FF interval
durations and the beat-to-beat changes in FF intervals were evaluated.
The latter was expressed as the absolute value of the percentage
difference to the preceding interval:
abs[(FFi-FFi-1)/FFix100].
Second, to grade the higher or lower regularity of the atrial
electrograms, we used the classification suggested by Wells et
al19 applied to the periods of 60 seconds used
for analysis of FF intervals. The presence and duration of the
three different types of AF in each site were expressed as a percentage
of the total duration of the analyzed period. This qualitative
analysis, although questionable and slightly approximate, was
performed to evaluate the presence of a more regular (type I) or more
irregular (type III) AF in the different atrial regions and to extend
the analyzed period of AF to reduce the bias of the spontaneous
fluctuation of AF activation.
The electrophysiologists who evaluated these data were unaware of the
part of the atrium analyzed and the results of the ablation.
Some months later, the measurements in eight patients were repeated
blindly by a second physician to assess the interobserver variability,
and in the other eight, the measurements were repeated by the same
electrophysiologist to evaluate the intraobserver variability.
Comparisons of the two analyses were performed by use of the
same chunk of recordings with unpaired t test
analysis.
Catheter Ablation
To exclude the presence of pericardial effusion, an echocardiogram was
performed after the procedure, 24 hours later, and during the day in
which the patient was discharged; intravenous heparin was
administered for 24 hours after the procedure, and then aspirin or
warfarin was administered, depending on the clinical situation, in each
patient for at least 1 month.
The ablation was considered successful if no recurrences of AF
lasting >30 seconds were present either with or without previously
ineffective drugs during the follow-up.
The patients were then followed up at 1, 3, 6, 9, 12, and 18 months or,
in the case of symptom recurrences, with ECG, clinical
examination, Holter, and echocardiography; all the
patients were taught to use a transtelephonic monitoring device for the
first 6 months. The presence of left and right atrial contraction was
evaluated with an echocardiogram at the follow-up examinations.
The results of atrial mapping in the patients with the different
results of catheter ablation were retrospectively analyzed. For
this purpose, the patients were divided into three groups: group A,
successful ablation; group B, unsuccessful ablation owing to AF
recurrences; and group C, unsuccessful ablation without AF
recurrences but with the appearance of new atypical atrial
flutter.
Finally, to evaluate a possible injury of vagal innervation, we
retrospectively evaluated heart rate variability in a time domain
analysis in the nine patients with successful ablation. Using a
Del Mar Avionics Strata-Scan 563, we calculated the SD of the NN
intervals, considering day (8 AM to 8 PM) and
night (midnight to 6 AM)
separately.
Statistical Analysis
Electrophysiological Findings
In the lateral right wall, type I and type II AF generally was
present (40.1% and 41.7% in the HL and LL for type I and 34.6%
and 34.2% in the HL and LL for type II), interrupted by briefer
periods of type III AF (HL, 25.3%; LL, 24.1%). Conversely, type II
and type III were mostly present in the septum (44.4% and 47% in
the HS and LS for type II and 42.4% and 46.3% in the HS and LS for
type III) and in the CS (37.5% and 48.5%, respectively), while type I
was present for shorter periods (HS, 13.2%; LS, 6.7%; and CS,
14.0%, respectively). In the HL and LL, type I was significantly
different with respect to the HS (P<0.01), LS
(P<0.01), and CS (P<0.05). Type III AF was
present for a shorter period in the HL than in the HS
(P<0.05), LS (P<0.05), and CS regions
(P<0.05) and in the LL than in the HS (P<0.01),
LS (P<0.01), and CS (P<0.05).
Ablation Results
The heart rate variability analysis performed after ablation in
the nine patients with successful ablation shows a greater mean RR
interval and SD of the NN interval in the night than in the day
(897±209 versus 785±124 ms and 90±44 ms versus 66±16 ms,
respectively); however, the difference did not reach statistical
significance, probably because of the small number of patients.
During follow-up (mean, 11±4 months; range, 4 to 19 months), nine
patients (56%) (group A) had stable sinus rhythm, four without any
antiarrhythmic drugs and five with a previously ineffective drug (Table 2
All the nine patients with stable sinus rhythm showed preserved atrial
contractility evaluated with
echocardiography in all the examinations during
follow-up. We did not observe any significant difference between the
group of patients with successful AF ablation and those in whom the
ablation was unsuccessful with regard to the ablation procedure
(duration of the procedure, fluoroscopic time, and number of RF
pulses). Moreover, echocardiographic findings and
clinical characteristics of AF (paroxysmal or persistent) did not
present any significant relationship with the results of AF
ablation and atrial mapping.
Atrial Mapping and Ablation Results
Group A patients had a longer mean FF interval in the lateral right
wall than group B patients, reaching statistical significance only for
the HL site (P=0.027) (Table 3
The beat-to-beat changes in FF intervals did not show any significant
difference between groups A and B for each examined region, even if the
right septal region had a higher variability in group A than in group
B. In group A, the beat-to-beat variability was lower in the lateral
region than in the other regions, but the differences reached
statistical significance only for the HL compared with LS
(P=0.01) and HS (P=0.007) (Table 3
In Table 5
Comparison Between Epochs a and b
In this study, performed in patients with idiopathic AF, we observed
during AF that different atrial regions showed different
electrophysiological behaviors with the
simultaneous presence of regions with relatively regular
activation and other areas with a completely disorganized atrial
activity. The AF pattern showed more regular and organized atrial
activity in the right lateral wall, as demonstrated by lower FF
beat-to-beat changes and by the higher percentage of type I and lower
percentage of type III AF compared with the other evaluated sites,
particularly the LS. These data are in accordance with what has been
reported by others in different experimental
situations.3 20 Morillo et
al3 observed longer intervals in the right free
wall than in the left free wall in dogs; however, no data are reported
for the interatrial septum. Similar results were found with only
qualitative analysis by Jais et al,20 who
evaluated, although not simultaneously, the regional
disparities of endocardial atrial activation in humans in a different
kind of population.
This nonhomogeneous
electrophysiological behavior may find an
explanation in the anatomy of the right atrium, which is a
rather complex structure, and in particular in the presence of the
crista terminalis. It is conceivable that this anatomic structure,
together with the tricuspid ring, may generally work as a functional
barrier, isolating the lateral and anterior wall from the other regions
of the right atrium and thus preventing the irregular spread in this
region of the multiple AF wavelets that have to follow a forced path,
forming an almost regular activation front, as suggested for atrial
flutter.23 Therefore, this area might be
protected from the appearance and/or perpetuation of multiple wavelets
and thus, at least in some patients, may not be a critical area for the
maintenance of AF but probably a bystander. On the other hand,
the more irregular atrial activity recorded in the LS may be
related to the finding of increased nonuniform anisotropic
characteristics observed in this region by Papageorgiou et
al.24 However, we must be aware that we cannot
exclude the possibility that the more irregular atrial activity
observed in the septum may depend on the fact that the catheter
positioned on the right septum may, to some extent, record the
wavelets circulating on both the right and left sides of the
septum.
Catheter Ablation
Few studies5 6 7 8 9 10 on AF catheter ablation in
humans are available, without any information on atrial mapping during
AF. Haissaguerre et al6 reported the results of
catheter ablation in patients with paroxysmal AF with and without
organic heart disease. Their success rate, including patients on
antiarrhythmic drugs, was 33% with a procedure limited to the right
atrium; the rate increased to 60% with additional ablation in the left
atrium.
Extensive ablation, however, especially in the left atrium, may be
related to an increased risk of complications such as thromboembolism.
To avoid these risks and because AF patients are a very
heterogeneous group, we selected patients with idiopathic
AF with the clinical characteristics of the so-called "vagal
AF."15 16 In fact, the increase in vagal tone
is considered the possible trigger of the arrhythmia, and the
effect of the vagal tone seems to be predominant in the right
atrium12–14; thus, we supposed that an ablation
limited to the right atrium might be effective.
The sites of RF lesions were decided on the basis of two observations.
First, some anatomic barriers are already present in the right
atrium; the septum is delimited by some of these (superior and
inferior vena cava, crista terminalis, CS os, tendon of
Todaro) and characterized by the presence in its center of a
nonhomogeneous structure, the fossa ovalis. Second, in our
experience from previous unpublished data, the septum was the region of
the right atrium in which more irregular and disorganized electrical
activity was recorded; assuming that this factor might be critical
for the maintenance of the AF, our ablation strategy considered
a linear lesion in the atrial septum to be the first step. The second
lesion was performed in the inferior vena cava–tricuspid
valve isthmus because the creation of a lesion from the superior to the
inferior vena cava could facilitate the reentrant circuit
of atrial flutter.23 25 The third transversal
lesion was performed in the first 12 patients in an attempt to
compartmentalize the right atrium as described by Haissaguerre et
al.8 However, considering the results of the
atrial mapping, the transversal lesion was not performed in the last 4
patients; in all of them, the ablation was successful.
In our study, we obtained successful ablation in nine patients (56%);
however, only four of them did not use drugs, while the other five
still needed drugs to maintain sinus rhythm. The modification of the
effect of antiarrhythmic drugs that were ineffective before the
ablation may be a sign that the
electrophysiological substrate has been
modified by the RF lesions. It may be hypothesized that if the lesion
created is not continuous enough to block the conduction in that area,
it could be sufficient to reduce the number of wavelets sustaining the
arrhythmia; therefore, the drugs may cause a further reduction
of the number of wavelets,14 thus preventing the
maintenance of AF.
Although the success rate is not very high, is similar to or higher
than that reported in the literature for an ablation limited to the
right atrium in humans, and is lower than that reported with a combined
right and left approach,6 our data show that at
least in some patients, catheter ablation in the right atrium only may
be effective in the "cure" of AF with a low risk of complications;
in fact, in our small group of patients, no major complication
occurred.
Atrial Mapping and Ablation Results
When we analyzed the differences between the patients with
successful and unsuccessful ablation, we found some interesting
findings, particularly their relationship with right atrial mapping.
The parameters that we analyzed, which are an
expression of different
electrophysiological characteristics, are
indeed concordant in showing that patients with successful ablation
generally present a peculiar pattern characterized by a
nonhomogeneity of the atrial activation in different regions of the
right atrium; this was less evident in patients with unsuccessful
ablation. Considering that in this study, RF was delivered mainly in
the septal area and that catheter ablation was more frequently
successful in those patients in whom the septum was the region of the
right atrium with the shortest FF interval and with the most irregular
activation compared with the lateral wall, we might hypothesize that in
these patients the lateral wall might be a bystander. These preliminary
data suggest that catheter ablation of AF might be guided by the
localization of critical areas necessary for the perpetuation of AF, at
least in some patients with idiopathic AF. This is in agreement with
the hypothesis recently suggested by Konings et
al26 that although the atria as a whole
participate in the process of AF, not all the parts of the atria
contribute equally to the perpetuation of the fibrillatory process,
suggesting that selective ablation of the areas characterized by
abnormal conduction patterns may be effective in the treatment of AF.
Moreover, the importance of the septum in the perpetuation of AF has
been recently highlighted by Kumagai et al,27 who
showed in dogs that a reentrant circuit in the septum may be a major
factor in the maintenance of this arrhythmia.
On the contrary, in patients with unsuccessful ablation, both the
lateral and the septal regions showed similar irregular activations;
therefore, in this case, the lateral wall may be directly involved in
the perpetuation of the arrhythmia. Possible explanations of
the unsuccessful ablation in these patients may be the difficulty in
creating continuous linear lesions in the lateral wall because of the
anatomy of this area or the need for either more detailed
atrial mapping with the evaluation of more sites or more extensive RF
lesions, including the left atrium.
Study Limitations
Other limitations are the small number of atrial sites considered for
the analysis of FF interval and AF pattern, which excluded the
posterior and anterior wall of the right atrium, and the fact that the
activation data of the left atrium were recorded with the catheter
positioned in the CS; these activations do not necessarily reflect the
left atrial endocardial activation.
Moreover, the analysis of the differences in the
electrophysiological features between
patients with successful and unsuccessful ablation was only
retrospective, and no attempt was made to modify the ablation strategy
on the basis of the atrial mapping. The lack of significance of AF type
differences in group B might be due to a type B error because of the
small number of patients.
Several limitations, although similar to those of the other clinical
studies on AF, are present, particularly the difficulty in
performing precise measurements of the FF interval when the atrial
activation is very irregular and the atrial electrograms are
fragmented, as they are in many cases during AF. We were not able to
use automatic measurements, thus allowing the analysis of AF in
periods of longer duration.
Finally, we cannot exclude the possibility that successful ablation may
depend on the lesion of vagal nervous endings, considering the kind of
population examined, even if the analysis of heart rate
variability suggested a preserved vagal tone modulation as indicated by
the day/night difference in the mean RR intervals and standard
deviation.
Conclusions
A period of 10 seconds seems to be long enough to evaluate
nonhomogeneous activation between the different regions of
the atria. The qualitative analysis of Wells' AF type gives
concordant results with the measurements of FF interval; therefore, the
former analysis, which is much faster than the latter, might be
used in the clinical evaluation of atrial activation during AF.
Right atrial catheter ablation has been found to be safe because no
complications occurred in any patient. An improvement in atrial mapping
is recommended to characterize better this heterogeneous
type of arrhythmia and consequently to evaluate whether it is
possible to differentiate various type of AF and to identify different
ablation strategies.
Received October 24, 1997;
revision received January 5, 1998;
accepted January 30, 1998.
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© 1998 American Heart Association, Inc.
Clinical Investigation and Reports
Atrial Mapping and Radiofrequency Catheter Ablation in Patients With Idiopathic Atrial Fibrillation
Electrophysiological Findings and Ablation Results
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Background—Knowledge of the
electrophysiological substrates and the
cure of atrial fibrillation (AF) is still unsatisfactory. The goal of
this study was to evaluate the
electrophysiological features of idiopathic
AF and their relationship to the results of radiofrequency (RF)
catheter ablation of AF and the safety and effectiveness of this
procedure.
Key Words: fibrillation • catheter ablation • electrophysiology • mapping
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
Atrial fibrillation
is the most frequent supraventricular arrhythmia;
despite this, its therapy is still unsatisfactory, probably because of
the few data known about atrial mapping during AF in different clinical
situations in humans.1 2 Recently, some studies
on animals3 4 and a few in
humans5 6 7 8 9 10 have demonstrated that selective
endocardial lesions in the right and/or left atrium may be effective in
the prevention of AF. These studies considered a
heterogeneous population and used different ablation
techniques that consisted of multiple RF lesions in both the right and
left atria in most cases. However, the creation of extensive lesions in
the left atrium is associated with a theoretical increased risk of
thromboembolism.11 Also, to the best of our
knowledge, no data are reported concerning the relationship between
atrial mapping and the success of the ablation procedure in humans.
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
Study Population
Sixteen consecutive patients highly symptomatic for
idiopathic AF with a clinical history suggestive of a vagal form as
described by Coumel15 and Prystowsky et
al16 and refractory to drug therapy (number of
drugs, 3±2), including class III drugs in all patients, were studied
(Table 1
). Mean age was 52±10 years, all
but 1 were men, and a history of AF was present from 7±6 years. In
all patients, a close link between the onset of the AF and enhanced
vagal tone was present; at the beginning of symptoms, most of the
episodes started during the night, after meals, and during rest; no
demonstrable organic heart disease was present in any patient. Left
and right atria were normal in 9 and 6 patients, respectively, and
moderately enlarged in the others. Eight patients had long-lasting
episodes (>7 days) defined as persistent, and 8 had paroxysmal AF with
daily sustained episodes. Patients with the paroxysmal form had a mean
value of 10.5 (range, 2 to 92) episodes per day, and AF was present
for a mean of 43.5±16.4% (range, 17% to 55%) of time as evaluated
with ECG Holter monitoring.
View this table:
[in a new window]
Table 1. Clinical Characteristics of Study Population
All patients gave written informed consent. Antiarrhythmic
drugs had been discontinued for at least five half-lives, and no
patients had received amiodarone in the preceding 6 months. The
electrophysiological study was performed by
use of two standard halo catheters (Cordis Webster) with 20 electrodes
and an interelectrode distance of 2–8-2 mm positioned in the
right atrium to map the lateral region and the septum of the right
atrium. An octopolar catheter with 2-mm interelectrode distance (Cordis
Webster) inserted into the distal CS was used to map the region of the
lateral wall of the left atrium adjacent to it. Bipolar digitized
atrial electrograms from 20 to 24 endocardial sites and two surface ECG
leads were simultaneously recorded (1-kHz sampling
frequency, 30- to 500-Hz band-pass filters), displayed on a
multichannel recorder, and stored on magneto-optical disks
(Cardiolab, Prucka Engineering, Inc). If AF was not spontaneously
present, it was induced with either atrial extrastimuli or atrial
bursts.
The atrial electrophysiological
parameters were analyzed during spontaneous or
induced episodes of AF lasting >5 minutes, excluding from the
analysis the first and last minutes of AF. The analysis
was made for each parameter on readings from the same
simultaneous time period in four sites of the right atrium:
HL, LL, HS, and LS and in the epicardial lateral wall of the left
atrium through the CS.
Catheter ablation was performed by use of either a standard
ablation catheter with a 4-mm electrode tip with thermistor (Blazer,
EPTechnologies) or special catheters with multiple 4-mm electrodes
(from four to six), each suitable for RF delivery with thermocouple
(Amazr Medtronic). Three linear lesions in the right atrium were
performed as described in Figure 1. On
the basis of our preliminary observations of the atrial
electrophysiological features during AF,
the third transversal lesion was not performed in the last four
patients. The fossa ovalis was localized with radiological landmarks
and transesophageal (Sonos 1000, 5-MHz Hewlett Packard)
or intracavitary echocardiography (ClearView Ultra,
20 or 10 MHz, Boston Scientific Corp), which were also used to check
the stability and tissue contact of the catheters. RF energy was
delivered with Atakr (Medtronic) or EPT 1000 (EP Technologies)
generators; RF energy was delivered setting the temperature to 60°C
for 60 seconds. No heparin was administered before or during the
procedure.
View larger version (39K):
[in a new window]
Figure 1. Diagram of the three linear lesions performed in
the right atrium. The first was a "septal" line from the superior
vena cava (SCV) to the fossa ovalis (FO) to the CS os and from this to
the inferior vena cava (ICV) (1). The second lesion was
performed in the inferior vena cava–tricuspid valve
isthmus (2). The third transversal lesion from the fossa ovalis through
the posterior wall to the lateral edge of the tricuspid annulus was
performed to compartmentalize the right atrium (3). T indicates
tricuspid valve.
Paired and unpaired t tests were used for statistical
analysis. Results were considered to be statistically
significant when P<0.05. All data, unless otherwise noted,
were expressed as mean±SD. All statistical analyses were
performed with the Statistica for Windows statistical program (Stat
Soft).
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
Intraobserver and Interobserver Variabilities
There were negligible intraobserver differences (1% to 2%) in
values of FF intervals. Also, no significant interobserver differences
were observed in duration of FF intervals (1% to 6%), Moreover, there
were no significant intraobserver and interobserver differences in the
duration of the three types of AF (2% to 5%).
We have analyzed 2 periods of 10 seconds, epochs a and b,
for a total of 13 785 AF beats measured. The following results refer
to epoch a. The mean FF interval was slightly longer in the HL and LL
(147±31 and 148±29 ms, respectively) compared with the HS and LS
(130±30 and 130±29 ms, P<0.05) and the distal CS (130±21
ms, P<0.05). The beat-to-beat changes in FF intervals were
lower in the lateral region (HL, 24±12%; LL, 24±12%) than in the
other regions (HS, 31±16%; LS, 33±14%; and CS, 30±15%), but the
statistical significance was reached only for the HL and LL compared
with the LS (P<0.05).
The procedure was performed during AF in 13 patients and
during sinus rhythm in 3 patients. At the end of the procedure, 4
patients (2 with paroxysmal and 2 with persistent AF) were in sinus
rhythm, and AF was no longer inducible. In these patients, the
interruption of AF occurred while performing the RF lesion in the
septum, and it was preceded by an organization of the atrial activity
in this region (Figure 2). In the other
12, the AF was still present or inducible. The results of RF
ablation are summarized in Table 2. The
mean duration of the procedure was 308±57 minutes with a mean
fluoroscopic time of 40±13 minutes. The mean number of RF pulses was
44±9. In 5 patients, two sessions were performed because of AF or
atypical flutter recurrences; another 2 patients refused the
second session. No complications occurred in any patients. In the 4
patients in sinus rhythm and no inducible AF, at the end of the
procedure, we were not able to demonstrate the presence of a block of
the conduction through the lines of lesion evaluated with atrial pacing
from different sites of the right atrium and CS; in all the patients, a
reduction in the amplitude and a fragmentation of the atrial
electrograms were generally observed in the sites where RF energy was
delivered.
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Figure 2. Example of AF interruption during RF delivery. A,
On the left, an irregular and disorganized atrial activity in the
septum is present, while the right lateral wall shows a rather
organized atrial activity. During RF delivery, on the right, the atrial
activity in the septum becomes more regular and organized with distinct
atrial electrograms. B, Some seconds later, continuing RF delivery,
interruption of AF occurs preceded by a further lengthening of the
atrial cycle. RF indicates artifact caused by RF delivery recorded
from the ablation catheter.
View this table:
[in a new window]
Table 2. Results of Radiofrequency Ablation 
and Figure 3). Of the other seven
patients (44%), five had AF recurrences (group B) and two
episodes of atypical atrial flutter (group C).
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[in a new window]
Figure 3. Follow-up results showing the number of patients,
expressed as a percentage, with successful ablation with or without
previously ineffective drugs and those with unsuccessful ablation. The
number of evaluated patients is indicated for each follow-up
period.
Patients with successful ablation (group A) showed different
electrophysiological features of the AF
compared with group B patients in whom the ablation was unsuccessful.
The two patients of group C were not considered for this
analysis because the group was too small. ). No differences in the FF intervals
were found between the two groups with respect to the other sites. In
Figure 4, the typical pattern of atrial
activity in a group A patient is presented and shows more
disorganized atrial activity in the septum and more organized activity
in the lateral wall where a craniocaudal or caudocranial activation
sequence is often recorded. Separate analyses of the two
groups showed that in group A, the FF intervals in the lateral right
wall were significantly longer than in the other sites, whereas this
finding was not observed in group B (Tables 3 and 4). Figure 5 shows the usual pattern of the
histograms of FF intervals in a group A and a group B patient.
View this table:
[in a new window]
Table 3. Mapping Results: FF Durations and Their Beat-to-Beat
Changes
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[in a new window]
Figure 4. Example of endocardial mapping during AF in
patient 1 showing the surface ECG in lead II and 11 bipolar endocardial
leads. The typical pattern of activity found in patients who underwent
successful ablation is evident, showing more disorganized activity in
the septum and more organized activity in the lateral wall with a
craniocaudal activation sequence; after some cycles there is an
inversion of the sequence with a caudocranial activation.
View this table:
[in a new window]
Table 4. Differences in FF Durations Between the Mapped Sites
in the Group With Successful Ablation (Group A) and the Group With
Unsuccessful Ablation (Group B)
View larger version (42K):
[in a new window]
Figure 5. Histograms of FF durations and time series of
beat-to-beat changes of FF intervals for all mapped sites. Shown on the
left is a representative successful ablation patient
(patient 4); on the right, a representative
unsuccessful ablation patient (patient 12). In the patient with
successful ablation, there is a marked difference between the
measurements in the lateral wall and the other sites. The lateral wall
histograms show an evident peak with a long average FF interval (HL,
161 ms; LL, 173 ms), whereas in the other sites, the histograms are
broader with a significantly lower average FF interval. The time series
of the lateral wall show reduced beat-to-beat changes compared with the
other sites. Whereas these differences between the lateral wall and the
other sites are evident in the patient with successful ablation, in the
patient with an unsuccessful ablation, there is no evident difference
in the various sites in either the average FF interval or beat-to-beat
variability. ). No
difference was observed for each analyzed site in group B.
Figure 5 shows the time series in a group A and a group B patient. , the mean duration (expressed
as a percentage) of the three types of AF in groups A and B for each
site are given. Groups A and B did not show any statistically
significant difference with regard to the types of AF, except for type
III, which was greater in group B than in group A in the HL region
(P<0.05), and type I, which was present mostly in the
HL region (P<0.05) in group A. As seen with the
analysis of the FF interval duration and the beat-to-beat
changes in FF interval, group A showed greater organization in the
lateral region than in the septum and CS, whereas group B showed no
significant differences in the mapped regions (Figure 5). In group A,
type I was more present in the HL and LL regions compared with the
HS, LS, and CS; however, this is statistically significant only for the
HL and LL compared with the HS (P<0.01) and LS
(P<0.05) (Figure 6). No
significant difference was observed for type II AF. In group A, type
III AF was more rarely present in the HL and LL than in the HS
(P<0.01) and LS (P<0.01). Only the HL showed a
significant difference for type III when the different sites were
compared with the CS (P<0.01). In group B, the types of AF
were similarly present in the mapped regions with no significant
differences.
View this table:
[in a new window]
Table 5. Mapping Results: AF Types
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[in a new window]
Figure 6. Duration of the three different types of AF
obtained expressed in percentage for all patients, the successful
ablation patients (group A), and the unsuccessful ablation patients
(group B).
In the total group of 16 patients, no statistically significant
difference was observed between epochs a and b for all sites
analyzed (HL, 147±31 versus 145±33; LL, 148±29 versus
150±35; HS, 130±30 versus 123±35; LS, 130±29 versus 119±31; and
CS, 130±21 versus 119±28, respectively). Moreover, a comparison of
epochs a and b did not show significant differences in patients with
successful (HL, 159±24 versus 157±22; LL, 156±28 versus 166±25; HS,
122±32 versus 117±32; LS, 126±28 versus 115±32; and CS, 132±20
versus 122±26, respectively) and unsuccessful (HL, 122±31 versus
118±37; LL, 128±28 versus 118±35; HS, 128±16 versus 116±34; LS,
127±34 versus 111±32; and CS, 119±23 versus 102±24, respectively)
ablation. Similarly, in epoch b, the difference between the septum and
the lateral right wall was similar to epoch a. In fact, FF intervals in
the lateral right wall were significantly longer than in the septum (HL
and LL versus HS and LS, P<0.01) and in CS
(P<0.01).
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
Atrial Mapping
Few studies have evaluated atrial activation during AF in humans,
and any atrial mapping was generally performed from the epicardium and
limited to the free walls, with the other regions of the atria and
particularly the septum excluded.1 2 Data dealing
with the spatial organization of AF are also
scarce.1 2 3 20 21 22
There are few data on endocardial catheter ablation of
AF.3 4 5 6 7 8 9 10 Recently, experimental studies dealing
with AF catheter ablation in animals have been
reported.3 4 Elvan et al4
evaluated AF inducibility after an ablation procedure that mimicked the
Maze procedure; on the contrary, Morillo et al3
showed the effectiveness of localized epicardial cryoablation in 11
dogs in the site where the shortest FF intervals were recorded.
The aim of catheter ablation of AF should be its cure while
limiting the extension of the lesions as much as possible; one of our
objectives in this study was to evaluate whether an analysis of
the atrial electrophysiological features
may lead to the identification of atrial regions that are critical for
the appearance and maintenance of the AF, thus limiting the RF
delivery to relatively small areas.
Some limitations are present in this study. The atrial mapping
was performed by use of bipolar recordings with a relatively
large interelectrode distance (2 mm); a closer interelectrode
distance or unipolar recordings would have allowed more precise
evaluation of the atrial activation with possible perturbation caused
by far-field activation excluded. We used unipolar recordings
in the first patients, but the disturbance of the isoelectric
line made correct evaluation of the FF intervals difficult.
In patients with idiopathic AF, different activation patterns
during AF may be simultaneously present; some regions
show more regular atrial activity, generally the right lateral wall,
while others such as the septum may show very irregular atrial
activation. Catheter ablation limited to the right atrium may be
effective in about half of the patients with idiopathic AF, although
most of them still may need previously ineffective drugs. However, this
suggests that the electrophysiological
substrate was modified. The success of the catheter ablation shows that
at least in some patients, the right atrium is primarily involved in
the genesis of the AF and that the patients with successful ablation
showed a peculiar electrophysiological
pattern characterized by more rapid and irregular atrial activity in
the septum than in the lateral wall.
Selected Abbreviations and Acronyms
AF
=
atrial fibrillation
CS
=
coronary sinus
HL
=
high lateral wall
HS
=
high septum
LL
=
low lateral wall
LS
=
low septum
RF
=
radiofrequency
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
1.
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mapping and description of the electrophysiologic basis of atrial
flutter and atrial fibrillation. J Thorac Cardiovasc
Surg. 1991;101:406–426.[Abstract]
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