International Journal of Arrhythmia 2013;14(1): 24-27.
Untitled Document
ECG & EP CASES
Radiofrequency Catheter Ablation of Persistent Atrial Fibrillation Using a New Open Irrigated Tip Catheter
Jaemin Shim, MD Division of Cardiology, Yonsei University Health System, Yonsei University College of Medicine, Seoul, Korea
Introduction
Radio frequency catheter ablation (RFCA) has
become an important treatment modality in
numerous cardiac rhythm disorders. Continued
development of catheters to improve efficacy and
safety of RFCA has led to the use of a saline
irrigated catheter to cool the electrode tip. Saline
irrigation allows for greater power application to the tissue and creates deeper lesions.1 The use of an
open irrigated catheter has become the standard
ablation technique, particularly for the ablation of
atrial fibrillation (AF). The Cool Flex™ablation
catheter is the first catheter with a fully irrigated,
flexible tip electrode designed to conform to the
cardiac anatomy, reduce operator transmitted force
into the tissue, and improve cooling performance.
This catheter has 4 open holes in the distal tip and
multiple slits in the lateral side that allow
preferential flow that directs the majority of the
saline toward the tip-tissue interface when the
catheter is flexed. We report our clinical experience
with the new irrigation catheter in a case of
persistent AF.
Case
A 73-year-old man was referred to our
institution for RFCA of AF. He had been treated for
symptomatic persistent AF for 3 years; however,
antiarrhythmic drugs including flecainide,
pilsicainide, and amiodarone failed to control his
symptoms. He had a history of essential
hypertension and under went RFCA for isthmusdependent
atrial flutter 5 years ago. On admission,
his physical examination was unremarkable and
electrocardiography showed AF with a heart rate of
59 bpm. Transthoracic echocardiography showed
left atrial (LA) enlargement with an anteriorposterior
diameter of 51 mm and normal ejection
fraction of 55%. Preoperative transesophageal
echocardiography showed no evidence of intracardiac
thrombus. According to our institution’s
protocol for persistent AF, the ablation lesion set
consisted of circumferential biantral ablation with
electrical pulmonary vein isolation and LA roof,
posterior-inferior line, anterior line, and superior
vena cave ablation (Figure 1A). Using the powercontrolled
mode fixed at 30-35W, radiofrequency
(RF) energy was delivered using the Cool Flex™
ablation catheter at each point while the tip of the
catheter was irrigated with 0.9% saline at a rate of
17 mL/minute. Individual RF delivery was applied
for approximately 20 seconds until the elimination
of the atrial potential. This was repeated if
necessary up to a maximum of 30 seconds. After
ablation, the catheter was moved to the next site
along the line. This was continued until ablation of
the standard set of lesions was complete.
Characteristically, RF application resulted in rapid
and complete atrial potential elimination and linear
ablation was performed quite rapidly without
residual potential. Bidirectional block was achieved
and confirmed by differential pacing maneuvers
(Figure 1B-D).
The total procedure time, fluoroscopic time, and ablation time were 217, 61,
and 82 minutes, respectively, which were shorter
than the average durations for persistent AF
ablation using a conventional irrigation tip catheter
(255, 73, and 94 minutes, respectively). As
expected, the irrigation volume was decreased by
1000 mL with the new catheter. There were no
steam pops, charring, or coagulum formation
during the procedure. The patient’s symptoms
disappeared and continuous Holter electrocardiography
recording showed no sustained
AF at 3 months after ablation. Antiarrhythmic
medications were discontinued after a 3 month
blanking period.
Discussion
Open irrigated catheters have been developed to
improve the efficacy and safety of RFCA and have
become the standard ablation technique for AF.2
Saline irrigation from the catheter cools the
electrode-tissue interface and enables the use of
more power, which results in increased heating and
deeper lesions while reducing the risk of thrombus
formation. The efficacy of open irrigated catheters
has been well documented in various types of
arrhythmias.3-5 However, there are several concerns
about the conventional irrigation catheter. First,
because conventional open irrigated catheters have
6 irrigation ports circumferentially arranged at the
distal tip of the ablation electrode, actual open
irrigation of the catheter provides uneven saline
perfusion that is mainly distributed away from the
tissue-electrode interface when the catheter tip is
parallel to the tissue. These differences in cooling
may produce marked variations in lesion formation
according to the catheter tip orientation. A more
global distribution of irrigation channels across the
ablating electrode would potentially provide
uniform cooling of the catheter tip and predictable
lesion formation irrespective of the electrode
orientation. Second, although open irrigated tip
catheters may reduce the incidence of coagulum
formation and charring during ablation by active
cooling, there is still a high potential for such
events to occur in areas away from the irrigation
channels, particularly where the electrode meets
the shaft. This can cause high peak temperatures in
this area and result in coagulum formation and
charring. Introducing irrigation ports at the
proximal end of the tip inaddition to the distal end
may reduce the incidence of coagulum development
and charring and provide more effective cooling.
Third, conventional irrigated tip catheters have
rigid distal tips and can not always adapt to cardiac
anatomy due to the limited contact area. Therefore,
ideal lesion formation is technically challenging and
time consuming. Finally, open irrigated catheters
carry the risk of fluid overloading in patients
requiring multiple linear ablations over a long
duration. A catheter with a lower fluid requirement
can diminish these fluid overload issues in
procedures involving AF. The Cool Flex™ is a
new irrigation catheter with a unique design that
was developed to overcome the limitations of
conventional catheters as described above. In the
present case, we experienced increased efficiency, a
shorter procedure time, and less fluid loading with
the new ablation catheter in a patient with
persistent AF. However, there is a paucity of data
regarding the use of the Cool Flex™catheter in AF
ablation and there are persistent concerns about its
safety. The Clinical Evaluation of Therapy™ Cool
Flex™Ablation Catheter for the Treatment of
Paroxysmal Atrial Fibrillation has been conducted
in Europe and more data on the efficiency, safety,
and optimal RF power of the catheter are expected
to be elucidated.
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