Right Atrial Angiographic Evaluation of
the Posterior Isthmus
Relevance for Ablation of Typical Atrial Flutter
Hein Heidbüchel, MD, PhD; Rik Willems, MD; Hennie van Rensburg, MD; Jef Adams, MS;
Hugo Ector, MD, PhD; Frans Van de Werf, MD, PhD
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Background—Gaining anatomic information about the posterior isthmus is not generally part of flutter ablation
procedures. We postulated that right atrial (RA) angiography could rationalize the ablation approach by revealing the
conformation of the isthmus.
Methods and Results—In 100 consecutive patients, biplane RA angiography was performed before ablation to guide
catheter contact with the isthmus along its length. Angiography showed a wide variation in the width of the isthmus (17
to 54 mm; 31.3⫾7.9), its angle with the inferior vena cava in the right anterior oblique projection (68° to 114°;
90.3⫾9.0°), and its lateral position relative to the inferior vena cava in the left anterior oblique projection. A deep
sub-Eustachian recess was revealed in 47%, with a mean depth of 4.3⫾2.1 mm (1.5 to 9.4). A Eustachian valve was
visualized in 24%. Ablation resulted in bidirectional conduction block (which could be transient) in all, with a median
of 2 dragging radiofrequency (RF) applications (2.3⫾2.5 RF applications; 57°C, ⱕ99 seconds each). Permanent block
was achieved in 99%, with a median of 3 RF applications (3.4⫾3.0). The presence of a Eustachian valve or concave
isthmus was associated with statistically more RF applications; the same trend was seen for patients with deep pouches.
The number of RF applications decreased statistically throughout the study, indicating a learning curve. No patient had
a recurrence after a follow-up of 13⫾11 months.
Conclusions—Right atrial angiography reveals a highly variable isthmus anatomy, often showing particular configurations
that can make ablation more laborious. Rational adaptation of the ablation approach to these anatomic findings may
contribute to successful ablation. (Circulation. 2000;101:2178-2184.)
Key Words: atrial flutter 䡲 catheter ablation 䡲 angiography 䡲 structure
F
lutter ablation usually targets the region between the
inferior vena cava (IVC) and the tricuspid annulus (TA)
(posterior isthmus).1– 4 Current procedures are based on electrical confirmation that the targeted isthmus is part of the
flutter circuit (eg, by entrainment pacing) and verify
the creation of bidirectional isthmus block by pacing in the
proximal coronary sinus (CS) or the posterolateral right
atrium.2,5 Although these techniques have led to a better
understanding of the arrhythmia circuit and of the end point
needed for a successful ablation outcome, information about
the anatomic characteristics of the isthmus remains scarce.
Anatomic reports in autopsied hearts have shown that its
structure can be highly variable.5– 8 However, gaining information about isthmus width, its morphology, and its delineation at the caval aspect by the Eustachian valve generally is
not part of the ablation procedure.
Revealing the anatomic structures in patients could be
accomplished by techniques such as transthoracic, trans-
esophageal or intracardiac echocardiography, MRI imaging,
or electroanatomic mapping.9,10 However, these can be time
consuming and/or cannot always be applied at the time of
ablation itself. Moreover, special equipment is required.
Right atrial angiography is a widely available and inexpensive alternative.11 We postulated that visualizing the anatomic
conformation of the isthmus could rationalize the ablation
approach.
Methods
Patients
We report on 100 consecutive patients (81 men) referred for ablation
of counterclockwise (99) and/or clockwise (9) atrial flutter (November 1995 to June 1999). Mean age was 55⫾13 years (range 13 to 77
years). Fifty patients had no manifest structural heart disease.
Electrophysiological Study and Ablation
The procedures were performed under propofol anesthesia (with
mechanical ventilation). Mapping (including use of a 20-polar halo
Received August 2, 1999; revision received November 30, 1999; accepted December 10, 1999.
From the Department of Cardiology, University Hospital Gasthuisberg, University of Leuven (Belgium).
Presented in part at the 20th Congress of the European Society of Cardiology, Vienna, Austria, August 1998.
Correspondence to Hein Heidbüchel, MD, PhD, Cardiology, University Hospital Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium. E-mail
[email protected]
© 2000 American Heart Association, Inc.
Circulation is available at http://www.circulationaha.org
2178
Heidbüchel et al
Angiographic Evaluation of the Posterior Isthmus
2179
catheter) and entrainment pacing confirmed the participation of the
isthmus in the arrhythmia circuit. Bidirectional block was verified by
pacing from the proximal CS and posterolateral right atrium (RA)
while mapping the atrial activation sequence and double potentials
along the entire ablation line.
Radiofrequency (RF) energy was delivered with the use of
thermistor ablation catheters with 6- or 8-mm tips (target 57°C; ⱕ50
W). If required by the anatomic configuration, sometimes a 4-mm-tip
catheter with appropriate curve was introduced later during the
procedure. An SR-0 and/or SAFL sheath (Daig Corp) was used to
support the ablation catheter in 8 and 9 patients, respectively. In
86%, current was delivered during pacing in the proximal CS and in
14% during flutter. During the initial RF applications (ⱕ99 seconds
each), the catheter was dragged from the TA toward the IVC.
Applications were stopped prematurely on catheter dislocation or the
occurrence of an impedance rise (n⫽4) or an audible “pop” (n⫽15).
After 1 or more RF applications without block, the ablation line was
mapped for a residual gap, and subsequent RF applications were
directed to this gap.4
After ablation, subcutaneous low-molecular-weight heparin was
given for 1 week and aspirin for 6 weeks, except in patients with a
history of atrial fibrillation, in whom oral anticoagulation was
continued.
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RA Angiography
Biplane angiography was performed after mapping and entrainment
and shortly before RF energy delivery, allowing maximal concordance of the catheter positions during angiography and ablation.
Right anterior oblique (RAO) and left anterior oblique (LAO) views
were individually adjusted so that the His bundle catheter projected
strictly parallel to the x-rays in the LAO view and that the CS
catheter made an angle of ⬇10° to 15° in the RAO view. The mean
RAO and LAO angles were 43⫾10° (15° to 70°) and 49⫾10° (26°
to 75°). A first injection was made with a 6F or 7F pigtail located at
the superior vena cava (SVC)-RA junction and a second at the IVC
(40 mL; 18 mL/s). A single injection inside the RA did not always
result in clear delineation of the SVC, IVC, and CS and tricuspid
orifices, right atrial appendage, and isthmus. The angiograms were
digitally acquired, allowing replay and storage of RAO and LAO
frames as references during the subsequent ablation.
In 51 patients, a quantitative analysis of different RA anatomic
structures was made on the latest atrial diastolic frame (confirmed by
the opening of the tricuspid valve in the next frame). Measurements
were calibrated by interelectrode spaces projecting perpendicular to
the given cine view. The width of the isthmus in the RAO view was
measured between the IVC and the lower hinge point of the tricuspid
valve (points A and B in Figure 1A). The isthmus often could be
divided into a recess (inferoposterior to the CS ostium) and a flat
vestibule (between this recess and the TA)11: The width of each was
measured. The perpendicular distance between the line connecting A
and B and the deepest point of the isthmus was quantified. Also, the
angle between line A-B and a line parallel to the ablation catheter in
the terminal IVC was evaluated. In the LAO view, the distance
between the lateral aspect of the IVC orifice and the position of the
ablation line (points C and D) was measured.
Statistical Analysis
Summary values are given as mean⫾SD if a normal distribution was
expected; otherwise median and range are used. Unpaired t tests
were used in the comparison of normal distributions, and MannWhitney rank sum tests or Kruskal-Wallis statistics were used in the
absence of the assumption of a normal distribution (eg, the number
of RF applications). A value of P⬍0.05 was considered significant.
Results
Anatomic Observations
Figure 1A shows contrast injections at the SVC and IVC
orifices, each visualizing the terminal part of the respective
vena cava and its RA junction. The isthmus generally could
Figure 1. Angiographic visualization of isthmus. A, Radiographs
in RAO and LAO projections during contrast injection at atrial
junction of SVC (upper panels) or IVC (lower panels). Isthmus
width was measured between IVC (A) and lower hinge point of
tricuspid valve (B). Figure shows “simple” isthmus with straight
appearance (ie, maximal distance between line A-B and isthmus
is ⱕ2 mm), average width (28 mm), and typical angle with ablation catheter in IVC (93°). Determination of lateral aspect of IVC
orifice in LAO view allowed later comparison with position of
ablation line in this view (C and D, respectively). RAA indicates
right atrial appendage. B, During ablation, catheter (6-mm tip)
was slowly withdrawn over isthmus from TA (upper panels)
toward IVC. In this patient, first dragging RF application resulted
in conduction block (after 80 seconds) exactly at junction with
IVC (lower panels). During application, contact with wall was
verified by use of stored angiographic images as references.
be evaluated better during the IVC injection, as expected.
Angiography revealed a profound variability in isthmus
anatomy. Its width varied from 17 to 54 mm (31.3⫾7.9)
(Figure 2). Also, the angle between the ablation catheter (in
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Figure 2. Variations in isthmus width. A, Wide isthmus (48 mm) making sharp angle with IVC (79°). Reaching tricuspid aspect of isthmus was key to successful creation of conduction block. Angiography showed that it could not be reached by first ablation catheter
(8 mm EPT, “extended curve”) even when introduced through specially designed long sheath (SAFL, Daig). Mapping also showed residual gap of conduction at TA after 4 RF applications. Fifth RF application, with 2.5-in catheter with proximal pull-wire (Cordis-Webster),
after angiographic and electrogram (atrioventricular amplitude [A/V] ⬍0.5) confirmation of positioning on TA, resulted in block. B,
Craniocaudally elongated atrium with very short isthmus (17 mm) targeted with 2-in catheter, resulting in block during second
application.
its terminal part in the IVC) and the isthmus varied from a
sharp angle of 68° to an open angle of 114° (90.3⫾9.0°)
(Table 1). An isthmus width of ⱖ39 mm or catheter-IVC
angle of ⱕ81° were both seen in only 18%. Each could result
in difficulty reaching the tricuspid aspect of the isthmus.
Their combination was present in 5% (Figure 2A). An
isthmus ⬍21.5 mm was seen in 12%.
More striking than differences in width was the recognition
of special anatomic configurations. In 31%, the maximal
perpendicular distance between a line connecting both ends
of the isthmus and the isthmus itself was ⱕ2 mm, leading to
TABLE 1.
an almost straight appearance (Figures 1A and 2A). In 22%,
however, the isthmus showed a more or less concave aspect
(Figure 3A), with a mean depth of 4.1⫾2.1 mm (2.2 to
9.3 mm) (Table 1). In the remaining 47%, the isthmus could
be divided in a flat vestibular part against the TA and a
pouchlike recess at the IVC side (Figure 3, B, C, and D).
Their lengths were 12.7⫾3.6 and 17.3⫾5.1 mm, respectively.
The average depth of this sub-Eustachian pouch was
4.3⫾2.1 mm. It was deeper than 5 mm in 18%. The presence
Angiographic Appearance of Posterior Isthmus
No. of patients (male/female)
Age, y
100 (81/19)
55⫾13
(13–77)
Isthmus width, mm
31.3⫾7.9
(17–54)
Straight aspect*
Concave aspect*
Concavity depth, mm
31
22
4.1⫾2.1
(2.2–9.3)
Vestibule⫹recess
Vestibule (tricuspid side, mm)
47
12.7⫾3.6
(5.4–19.2)
Recess (IVC side, mm)
17.3⫾5.1
(9.5–27.4)
Recess depth, mm
4.3⫾2.1
(1.5–9.4)
Prominent Eustachian valve, n
Angle between ablation catheter in terminal
IVC and isthmus
24
90.3⫾9.0°
(68–114°)
*Maximal perpendicular distance between the line IVC–tricuspid ring and the
isthmus was ⱕ2 mm (straight) or ⬎2 mm (concave).
Figure 3. Variations in isthmus morphology from concave to
aneurysmal. In ⬇50% of patients, isthmus had more or less
pronounced global concave aspect (ie, maximal distance
between line A-B and isthmus is ⬎2 mm; A). In 47% of patients,
flat vestibular part against tricuspid ring could be distinguished
from sub-Eustachian recess at IVC side. Latter could have
almost aneurysmal aspect (B through D).
Heidbüchel et al
Angiographic Evaluation of the Posterior Isthmus
2181
Figure 4. Variations in isthmus morphology: Eustachian valve. In 24% of patients, Eustachian valve could be visualized (A). In this
patient, after first RF application on tricuspid aspect of isthmus (B; 2.5-in proximal pull wire), ablation catheter with shorter curve (1.5
inches) was introduced to target area immediately behind Eustachian valve (C). Completion of ablation line in this way resulted in conduction block with second RF application. Also note loop in ventricular pacing lead (moving in and out of RV) and atrial lead prolapsing
through tricuspid valve after pacemaker implantation 6 years earlier (in another center).
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of a limited “neck” sometimes gave it an aneurysmal aspect
(Figure 3D).
Moreover, in 24% of the patients, a Eustachian valve could
be visualized between the IVC orifice and the isthmus. Often,
it had a membranous aspect, but it could be thick (as shown
in Figure 4A).
None of the morphological features (length or depth of the
isthmus or its parts, or presence of a recess or Eustachian
valve) was related to age, sex, or the presence of structural
heart disease.
Relevance for the Ablation Approach
The angiographic images helped to evaluate the position of
the ablation tip in the RAO projection before and during RF
application. Current application at the TA was started only
after electrical confirmation (ie, atrioventricular amplitude
[A/V] ratio of ⬍0.50) and angiographic confirmation that the
ablation catheter straddled the annulus (Figure 2A). The
initial ablation catheter was chosen after the angiography and
was generally a 2.5-in catheter with a proximal pull-wire
(6-mm tip; 85% in the last 50 cases). In 18 patients with a
long isthmus (ⱖ40 mm), the insertion of a 3-in catheter was
necessary in 6 and/or the insertion of a guiding sheath in 7.
Two different ablation approaches were taken when a deep
pouch was encountered: In 94% (44 of 47), the ablation
catheter was explicitly directed into it (often with the use of
a catheter different from the one chosen to ablate the
vestibular part of the isthmus), whereas the aneurysm was
avoided in 3 by ablation at the septal side of it.
Ablation catheters with a very short curve able to reach the
isthmus immediately behind the Eustachian valve (ie, 1.5-in
Cordis-Webster or a “small curve” EPT Blazer) were used
significantly more often in the presence of a valve (46% vs 5%,
P⬍0.001) to complete the ablation line (Figure 4, B and C).
Isthmus block often coincided with full completion of a
dragging RF application from the TA to the IVC (Figure 1B).
Interestingly, in 12 of the 46 patients in whom the first
application resulted in block, it was achieved before completely finishing the dragging movement over the anatomically defined isthmus. This indicated that conducting tissue
participating in the arrhythmia circuit was not contained
throughout the entire width of the isthmus.
Also, the position of the ablation line in the LAO projection was variable. In 36 patients, it was positioned rightsided of the lateral IVC edge, resulting in an oblique course
of the ablation catheter (Figure 5). The distance between the
lateral aspect of the IVC and the mid ablation catheter
position on the isthmus (C and D in Figure 1) varied from 13
to 0 mm (4.3⫾3.9 mm).
Ablation Results
Conduction block (which could be transient) was achieved in
all patients with a median of 2 RF applications (2.3⫾2.5).
Figure 6A shows their distributions: In the last 50 patients, no
Figure 5. Lateral displacement of ablation line relative to IVC orifice. In 36%, ablation catheter (RF) had to be directed more or less
obliquely over isthmus as viewed in LAO projection, with catheter positioned laterally from right edge of IVC (compare with position of
ablation catheter in Figure 1B).
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Figure 6. Distribution of number of RF applications. A, Distribution of number of RF applications required to achieve first
occurrence of bidirectional block. This block was permanent in
only 49% (with recurrence of conduction occurring from 10 seconds to 30 minutes). Lighter shaded bars represent results in
last 50 patients. B, Distribution of number of RF applications
required to achieve permanent block. In last 50 patients, outlier
values were absent, largest number of RF applications being 6.
more than 5 RF applications were required to achieve a first
block. Early recurrence of conduction after prior block was
seen in 51 patients. Additional applications led to permanent
block in 99% of the patients, with a median of 3 RF
applications (3.4⫾3.0; Figure 6B). The median energy delivered before first or permanent block was 4913 J (6952⫾8390
J) and 7540 J (9890⫾10 725 J), respectively. In 1 patient,
only transient block could be achieved from the 18th application on. No permanent block was present after 25 RF
applications, but the block cycle length had increased from
240 to 600 ms.
Because we adapted the ablation approach to the observed
anatomy, catheters were often exchanged. A mean of 2.0⫾0.9
catheters were used per patient (median 2; 1 to 5). This was
not significantly different among the various anatomic subgroups, although there was a trend for a higher number of
catheters in patients with Eustachian valves or aneurysmal
isthmus.
The presence of a Eustachian valve also led to a significantly higher number of applications to achieve both first and
permanent block (Table 2). After the first such cases, we
realized that targeting the area immediately behind the
Eustachian valve was the key to success, requiring a catheter
with a short curve (compare with supra; after 1 or 2
applications with a longer-reaching catheter). This explains
the clear trend for fewer RF applications in this subgroup in
the last half of the study compared with the first (median 3 vs
7; 3.1⫾1.4 vs 6.7⫾5.3; P⫽0.17). No patient in this group
required more than 6 RF applications in the last half of the
study. This also explains the significantly more frequent use
of 4-mm tips in the presence of a Eustachian valve
(P⬍0.001), whereas the distribution of 8- or 6-mm ablation
tips was otherwise not related to the ablation outcome or
anatomic configuration. Also, a concave aspect of the isthmus
was significantly related to a higher number of RF applications to achieve permanent block, and there was a clear trend
for a similar observation in the presence of a sub-Eustachian
recess. The number of RF applications was not related to the
position of the ablation catheter in the LAO projection.
Table 2 also illustrates a manifest learning curve throughout the study. When the patient group was subdivided into
thirds, the numbers of RF applications required to achieve a
first and a permanent block decreased statistically. In the last
34 patients, the median had decreased to 1 and 2 RF
applications, respectively. The corresponding energies delivered were 3820 J (5554⫾3470 J) and 5920 J (6960⫾4820 J).
This effect was seen as a trend throughout all anatomic
subgroups, but it did not reach statistical significance because
of the smaller number of observations.
The mean procedure and fluoroscopy times in all patients
were 119⫾50 minutes and 26⫾14.8 minutes (90⫾24 minutes
and 19.8⫾6.6 minutes in the last 34 patients). One patient had
a groin hematoma requiring surgical exploration. Minor
complications occurred in 5 patients. The angiography itself
and RF delivery did not result in any adverse event.
After a mean follow-up of 13⫾11 months, no patient has
had a recurrence of atrial flutter, including the patient with
only transient block. Thirty patients had at least 1 episode of
atrial fibrillation after a mean of 45 days.
Discussion
Previous anatomic reports studying post mortem human
hearts have pointed to the anatomic variability of the isthmus,
reporting an average width of 27⫾3.3 mm (Reference 7) to
31⫾4 mm.6,8 These values correspond well with our angiographic findings of 31.3⫾7.9 mm. Interestingly, Wang et al6
reported on the presence of a prominent nonfenestrated
Eustachian valve and of a thick, muscular-type Eustachian
ridge in 10% and 20%, respectively, whereas we found
evidence for such a structure in 24%.
There are very few anatomic data about this region in
patients in general or in patients with flutter in particular.12,13
Cabrera et al11 recently reported on angiographic measurements in 23 patients and found a mean isthmus width of
37⫾8 mm. Also, their values for the relative length of the
tricuspid vestibule and IVC recess are close to ours. Transthoracic and transesophageal isthmus evaluation in 105 patients after ablation for atrial flutter revealed similar variability in width and isthmus-IVC angulation.10
Thus far, almost no efforts have been made to adapt the
ablation approach to the anatomic peculiarities of the isthmus
in a given patient. Our findings show that a universal ablation
approach for atrial flutter may not be optimal. We individualized the ablation approach, depending on the angiographic
Heidbüchel et al
Angiographic Evaluation of the Posterior Isthmus
2183
TABLE 2. Number of RF Applications Required to Create Bidirectional Isthmus Block (First
Occurrence—Possibly Transient—and Permanent)
First Block
Whole study
X⫾SD
(range)
Median
2.3⫾2.5
2
Mean
Rank
Permanent Block
P
(1–18)
1st third (n⫽33)
3.2⫾3.9
2.0⫾1.4
3rd third (n⫽34)
1.7⫾0.9
Median
3.4⫾3.0
3
Mean
Rank
P
(1–22)
2
58.3
4.6⫾4.6
(1–18)
2nd third (n⫽33)
X⫾SD
(range)
3
58.0
3
54.8
2
37.8
(1–22)*
2
48.4
0.14 vs 1st
3.3⫾1.7
1
44.9
0.05 vs 1st
2.3⫾1.5
NS vs 2nd
(1–6)
(1–7)
NS vs 1st
(1–8)
(1–4)
0.008 vs 1st
0.007 vs 2nd
Isthmus aspect
Straight
2.4⫾3.1
2
48.6
2.6⫾1.5
(1–18)
Concave
2.2⫾1.5
2
54.7
NS vs straight
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(1–7)
Pouch
2.3⫾2.4
2
42.5
3
56.8
0.05 vs straight
3
51.6
0.18 vs straight
(1–6)*
3.3⫾1.5
(1–7)
2
49.8
(1–15)
NS vs straight
3.9⫾4.1
NS vs concave
(1–22)
NS vs concave
Eustachian valve
Present (n⫽24)
2.8⫾1.9
Absent (n⫽76)
2.1⫾2.6
2
65.8
1
45.7
4.5⫾3.7
(1–9)
3
59.7
3
46.9
3
47.7
3
54.1
(1.17)
0.002
(1–18)
3.0⫾2.7
0.05
(1–22)
Isthmus lateral from IVC (LAO)
No (n⫽64)
2.1⫾2.3
2
48.8
3.0⫾2.1
(1–18)
Yes (n⫽36)
2.6⫾2.7
(1–11)
2
53.5
(1–15)
NS
4.0⫾4.2
NS
(1–22)
*No permanent block in 1 patient.
findings. In many patients, a combination of catheters was
required to ensure adequate contact along the entire isthmus.
This was especially true if there was a deep sub-Eustachian
pouch, a concave deformation of the isthmus, or the presence
of a Eustachian valve. These more complex anatomic configurations also led to a significantly higher number of
required RF applications.
Cabrera et al8 described the IVC side of the isthmus as the
membranous part because it did not contain musculature (and
hence should not contribute to conduction). It could be up to
22 mm wide. This anatomic finding correlates with our observation that in 26% of the patients with isthmus block during the
first application, it was achieved before completely finishing the
dragging application from the TA toward the IVC.
Because this was not a randomized study between ablation
with or without angiography, we cannot conclude that performing angiography is superior. Nevertheless, apart from the
clear rationale of such an approach as outlined above, there
are other arguments for the added value of angiography: (1)
even when comparing only with those reports that used
dragging RF applications, block was achieved in more
patients and with fewer RF applications.2,9,14,15 We did not
use high-energy devices such as cooled electrodes16 and we
limited tip temperature to 57°C and power to 50 W; (2) there
was a clear learning-curve effect between the first, second,
and third thirds of our series (Table 2), without changes in
types of catheter or RF generator settings.
Other potential techniques for visualizing the isthmus
conformation are intracardiac echocardiography or electroanatomic mapping. Further evaluation will be necessary to
directly compare these approaches (which require special
equipment) with the more widely available angiographic
evaluation.
Although angiography may be useful for determining
contact with the wall in the RAO projection and for targeting
specific anatomic substrates, it provides little information for
the positioning in the LAO projection. Catheter position in
the LAO projection was mainly determined by the stability of
the catheter on the isthmus, although we tried to avoid the
septal aspect because of the higher risk of atrioventricular
block17,18 and the thicker myocardium at that site. Even if a
more oblique positioning of the ablation tip was required, it
did not lead to a higher number of RF applications.
Because the definition of “1 application” varies widely (from
discrete lesions with stepwise repositioning between applica-
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tions1,3 to dragging applications2,9,14,15), it is difficult to compare
the number of applications between different reports. Moreover,
power settings and duration of the applications may vary.
Therefore, in addition to the number of RF applications, we also
reported the cumulative delivered energy (in Joules). It may
serve as comparison for future reports.
We have no explanation for the inability to achieve permanent
block in a single patient. Although the isthmus was relatively
long, it had a straight aspect without any particular anatomic
features. The repeated transient block and the wide separation of
local electrograms without intermediate activity may suggest a
deep connection. An irrigated-tip ablation catheter could be
useful in such cases.16
We conclude that RA angiography is easy to perform and well
tolerated. It reveals a highly variable isthmus anatomy, often
showing particular configurations. Obstacles such as Eustachian
valves, aneurysmal pouches, or even a concave deformation of
the entire isthmus lead to more difficult ablation sessions.
However, adaptation of the ablation approach to these angiographic anatomic findings is rational and may help to ablate this
drug-defying arrhythmia with high success.
Acknowledgments
This study was supported in part by a research grant from Astra
Pharmaceuticals Belgium. Dr Heidbüchel is a Clinical Investigator
of the Fund for Scientific Research-Flanders.
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2. Poty H, Saoudi N, Abdel Aziz A, et al. Radiofrequency catheter ablation
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Right Atrial Angiographic Evaluation of the Posterior Isthmus: Relevance for Ablation of
Typical Atrial Flutter
Hein Heidbüchel, Rik Willems, Hennie van Rensburg, Jef Adams, Hugo Ector and Frans Van de
Werf
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Circulation. 2000;101:2178-2184
doi: 10.1161/01.CIR.101.18.2178
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