Introduction
Endocardial radiofrequency (RF) catheter ablation of accessory pathways (APs) is the
standard therapy for patients with AP-mediated atrioventricular reentrant tachycardia.
1
Endocardial catheter ablation has some limitations, such as the inability to access
intramural or epicardial portions of the arrhythmia circuits. Epicardial location
has also been related a contributing factor in up to 8% of failed RF ablations.
2
To date, only 3 cases of APs located near the mitral-aortic continuity and ablated
from the left coronary cusp have been reported.3, 4, 5
Key Teaching Points
•
A left coronary cusp location should be suspected in cases of electrocardiogram with
preexcitation, “w” in DI, and left anterosuperior accessory pathway (AP) precordial
suggestive pattern.
•
In cases with retrograde aortic approach and no early ventricular activation in the
left ventricle, the left sinus of Valsalva should be considered and explored.
•
In difficult left APs it is recommended to explore the distal coronary sinus as well
as the left atrial appendage with an initial transseptal approach and a secondary
retrograde aortic approach.
Case report
We describe the case of an 18-year-old woman with Wolff-Parkinson-White syndrome and
recurrent supraventricular tachycardia referred to our institution for a redo procedure.
The patient had a history of a left AP with a previous failed conventional ablation
6 months earlier with a retrograde approach in anterosuperior left ventricular aspect.
Echocardiogram confirmed normal ejection fraction and absence of evident structural
heart disease. Electrocardiogram (ECG) at the beginning of the study showed a manifest
preexcitation, with sinus rhythm and delta wave (+) in DII, DIII, (-) in AVL, and
with a “w” pattern in DI, (+/-) in V1, and (-) in V2 (Figure 1A). The electrophysiological
study demonstrated eccentric atrioventricular activation (Figure 1D), refractory period
of the AP <250 ms with no decremental properties, and orthodromic reentrant tachycardia
induced with atrial decremental stimulation (Figure 1B and E). Transseptal puncture
was performed using conventional references (a decapolar catheter in the coronary
sinus [CS] and quadripolar catheter in His). An open-irrigated ablation catheter (ThermoCool
SmartTouch; Biosense Webster, Irvine, CA) was advanced to the site of earliest ventricular
activation at the base of the left atrial appendage (LAA) guided by an electroanatomical
mapping system (CARTO3; Biosense Webster). Location of the catheter was confirmed
after angiography of the LAA (Figure 2A and Supplemental Video 1). RF ablation (with
a power of 30 W with an irrigation rate of 17 mL/h) at this location was unsuccessful.
Earliest ventricular insertion mapping was performed in the anterosuperior left ventricle
region as well as CS without remarkable precocity. Finally, throughout the retrograde
approach, the left sinus of Valsalva (SoV) region was explored. Selective angiography
through the cooled-tip ablation catheter was performed. A single RF application was
performed with 5 grams force and 20 W at 30 mL/h, where an early ventricular activation
was identified with a suggestive Kent potential leading to elimination of the AP within
2.5 seconds, so ablation power was titrated upwards (30 W at 30 mL/h) and continued
for 1 minute (Figures 2B–D and 3A–B, Supplemental Videos 2 and 3). Finally, ventricular
stimulation during adenosine injection confirmed the success of the procedure. No
complications were observed after the procedure and the patient remained without either
preexcitation reappearance or AP-mediated tachycardia during 10 months of follow-up
(Figure 1C).
Figure 1
A: Twelve-lead electrocardiogram (ECG) showing sinus rhythm and atrioventricular preexcitation.
B: Twelve-lead ECG during orthodromic reentrant tachycardia with 470 ms cycle length.
C: Twelve-lead ECG demonstrating sinus rhythm and lack of preexcitation. D: Twelve-lead
ECG in sinus rhythm and atrioventricular mild preexcitation with decapolar catheter
electrogram in coronary sinus demonstrating eccentric atrioventricular activation.
E:Twelve-lead ECG and endocavitary electrograms during orthodromic reentrant tachycardia.
Figure 2
A: Left atrial appendage angiogram in left anterior oblique view. B: Fluoroscopic
image of decapolar catheter in coronary sinus, quadripolar catheter in His, and radiofrequency
catheter at ablation site. C: Electroanatomic activation mapping in left anterior
oblique view with catheter in ablation site. D: Electroanatomic activation mapping
in right anterior oblique view with catheter in ablation site. CS = decapolar catheter
in coronary sinus; His = quadripolar catheter in His potential site; RF = radiofrequency
ablation catheter; RV = quadripolar catheter in right ventricle.
Figure 3
A: Twelve-lead electrocardiogram (ECG) and local electrogram at site of anterolateral
pathway before ablation. B: Twelve-lead ECG and local electrogram at site of anterolateral
pathway during and after ablation. Red arrow shows Kent potential (speed: 50 mm/s).
RF = radiofrequency ablation.
Discussion
The most frequent reasons for prolonged or failed AP ablation include inability to
reach the appropriate AP course, catheter stability, inadequate contact tissue, and
the presence of epicardial APs.
6
,
7
Other factors include accurate electroanatomical mapping of some atypical located
APs, such as the one described in this case, as well as multiple APs, slanted pathways,
the broad-based nature of the connection, and close proximity to atrial appendage
or major coronary artery.
8
To date, only 3 cases of APs ablated from the left coronary cusp have been reported.3,
4, 5
Sacher and colleagues
9
described the characteristics of patients after a prior failed ablation, which included
inaccurate mapping, epicardial AP, or APs that lie near or within the coronary sinus.
Identification of the AP location by means of the ECG is sometimes challenging. They
can be suspected when there is a manifest preexcitation. A “w” pattern in DI (although
not exclusive of these APs, since it can also be found in outflow tract premature
ventricular complex) is very characteristics of APs from the SoV, along with an early
precordial R/S transition in precordial leads, with transition appearing in lead V3
or later.
10
,
11
Under our point of view, some take-home messages can be drawn from this case report.
First of all, it is mandatory to do a precise examination of the ECG, at baseline
or after pacing maneuvers aimed to increase the degree of preexcitation. This is important
because the accuracy of the commonly accepted location algorithms improves with maximal
preexcitation.12, 13, 14 Nevertheless, it must be highlighted that atypical APs are
not represented in these algorithms. Subsequently, a step-wise strategy for mapping
and ablation of these atypical APs is needed. Exploration of the distal CS and great
cardiac vein is also recommended in patients with failed prior ablations. In this
setting the current electroanatomic mapping systems can assist in the detailed course
and location of these pathways, which very often, as was the case in our patient,
require a transseptal access.
9
Potential limitations in this case should be considered, such as the absence of mapping
during supraventricular tachycardia and the lack of use of a high-density catheter
or intracardiac echocardiography. Even though we consider the importance of thoughtful
use of fluoroscopy, angiography of the LAA and of other structures is also at times
very helpful, since it is useful to determine the location of the appendage and its
size and morphology in order to avoid complications and assure safe ablation in a
complex region of the myocardium.
In summary, under our point of view, in those patients with previous unsuccessful
ablation procedures in the vicinity of the LAA region it is important to reevaluate
alternative approaches, either by retrograde or anterograde access, in order to explore
the left ventricular anterosuperior region, the mitral-aortic continuity, and the
SoV. Importantly, prior to the RF application, selective angiography through a cooled-tip
catheter can be performed in order to avoid collateral damage to nearby coronary arteries.
15
Conclusion
We report a case of an AP successfully ablated from the left coronary cusp. Atypical
locations such as the one herein described must be taken into account when dealing
with challenging APs. Particular considerations at the time of mapping and ablation
of these locations need to be addressed in order to avoid potential complications.