Thrombus formation on the ablation line after pulmonary vein isolation
with a cryoballoon.
Yoshiki Kitazumi, MD, Daisuke Yuji, MD, PhD, Kouichi Nagashima, MD, PhD,
Akira Sezai, MD, PhD, Masashi Tanaka, MD, PhD
Department of Cardiovascular Surgery
Nihon University School of Medicine, Tokyo, Japan
Short running title: Ablation area thrombus formation
Address for correspondence: Kitazumi Yoshiki
Department of Cardiovascular surgery, Nihon University School of
Medicine
30-1 Ohyaguchi-kamicho, Itabashi-ku, Tokyo 173-8610, Japan
Tel: +81-3-3972-8111
Fax: +81-3-3972-1098
E-mail: kitazumi.yoshiki@nihon-u.ac.jp
The authors declare no conflicts of interest associated with this
manuscript.
Abstract
Catheter
ablation is a widely accepted therapy for atrial fibrillation (AF), of
which stroke is a major complication. A stroke after catheter ablation
has been reported in numerous studies not only in the acute phase but
also in the chronic phase. A 66-year-old man with drug refractory
paroxysmal AF underwent catheter ablation. Fourteen months later, the
patient was diagnosed with cerebral infarction. Transesophageal
echocardiography detected an ovoid mass on the anterior aspect of the
right superior pulmonary vein atrium, where the previous ablation was
performed. We report a very rare case of left atrial thrombus formation
required surgical treatment 14 months after cryoballoon ablation.Careful
follow up with multimodalities is necessary for the detection and
diagnosis of chronic phrase thrombus formation.
Keywords: Left Atrial Thrombus, Atrial Fibrillation, Cryoballoon,
Catheter Ablation
Introduction
Catheter ablation by means of radiofrequency (RF) energy or cryoballoon
is a widely accepted, non-pharmacological therapy for atrial
fibrillation (AF). However procedure-related stroke is a serious
complication. Stroke is primarily caused by thromboembolism during the
ablation and further appropriate anticoagulant therapy is crucial.1 Despite appropriate anticoagulation, the stroke may
be due to late left atrial (LA) thrombus formation in chronic phase.
Only two previous cases of LA thrombus post pulmonary vein isolation
(PVI) in the chronic phase have been reported. 2,3 We
encountered a rare case of late detected LA thrombus, following
cryoballoon ablation.
Case presentation
A 66-year-old man with drug-refractory paroxysmal AF was referred to our
institution for initial catheter ablation. The patient posed a low risk
for stroke as he was without any concomitant diseases such as
hypertension or hyperlipidemia, only slight high body mass index of 27
kg/m2. (CHA2DS2-Vasc score: 1 point). Transthoracic echocardiography
(TTE) revealed slight LA dilation that was 39mm in diameter, and
transesophageal echocardiography (TEE) detected no LA thrombus. PVI was
performed with a 28 mm cryoballoon (ARC-Adv-CB, Arctic Front Advance;
Medtronic Inc., Minneapolis, MN9 guided by Ensite NavX Velocity mapping
(Abbott Laboratories, Abbott Park, IL). Intravenous heparin was
administered to maintain an activated clotting time of >
300s during the procedure. Although sustained AF remained inducible
after PVI, no additional LA ablation was performed. The patient was
managed with oral dose of 100 mg bepridil, 20 mg aprindine, and 5 mg
apixaban twice daily. Electrocardiogram (ECG) and Holter monitoring
detected no AF recurrence throughout follow-up.
Fourteen months after PVI, the patient arrived at our emergency
department with left arm paralysis. Brain computed tomography (CT) and
magnetic resonance imaging (MRI) revealed cerebral infarctions of the
subcortical regions of bilateral temporal lobes, suggestive of embolic
shower. ECG monitoring revealed no AF recurrence during hospitalization.
The patient continued to take bepridil and apixaban until admission. TEE
detected no thrombus in the LA appendage (LAA), but an ovoid mass 15 mm
in diameter was observed on the anterior aspect of the right superior PV
antrum (Fig 1A,B). Contrasted-enhanced CT revealed that the location of
the mass matched the previous ablation area (Fig 1C). Due to the episode
of embolic shower, surgical resection was performed to prevent further
cerebral infarction. Resection of the LA mass followed by Cox Maze
procedure and LAA resection was performed. The mass was 12 mm in
diameter above the ablation line, consisted of smoothly marginated soft
tissue, and was excised easily (Fig 2A,B). Histologic examination
revealed that the thrombus adhered to the LA endocardium. Layers of
organized thrombus were formed on endocardium and fibrin thrombi were
above them. Part of endocardium was replaced with necrotic tissue and
structure of muscle layer was collapsed. Epicardium consists loose
collagen fibers with inflammatory cells and neocapillaries are formed
(Fig 3). The patient was discharged given the favorable clinical course
after surgery. At his several follow up visit, the patient was managed
with 100 mg flecainide and 5 mg apixaban twice a day orally, and no
recurrence of stroke or AF ensued for 20 months.
Discussion
Cryoballoom ablation-related stroke in the acute phase occurs rarely,
with a reported incidence of 0.2%4. However, its
occurrence in the chronic phase has been unknown. Based on the data, its
incidence of LA thrombus formation associated with cryoballoon ablation
is estimated to be even lower. In the patient considered here, the
mechanism of LA thrombus formation appeared to differ from that of AF,
because the patient was at low risk for stroke and symptoms were managed
with apixaban. Also, TEE revealed no thrombus of the LAA. Histological
findings of thrombus adhesion to the LA endocardium, which had been
replaced with necrotic tissue, might also support our hypothesis. Based
on these findings, LA endothelium damage due to the cryo-thermal energy
might be a main cause of thrombus formation, although cryoballoon
ablation was likely less damaging to LA endothelium or endocardium than
ablation5. Therefore, adding antithrombotic therapy to
anticoagulant therapy might be warranted in these patients. TEE is a
useful modality for detecting LA thrombus, most of which occur in the
LAA as a result of decreased outflow velocity. However, uncommon
thrombus locations such as the septum and previous PVI have been
reported2,3,6. In these cases, differentiation of the
thrombus from the myxoma is crucial for determining a treatment
strategy. Determination of a narrow stroke between a thrombus and myxoma
is not always straightforward6,7. Use of multiple
modalities, such as CT or MRI, might facilitate a correct diagnosis.
Conclusion
We encountered a rare case with late LA thrombus within a previous
cryo-ablation area. When monitoring the AF patients post-ablation,
clinicians should be aware of the possibility of late LA thrombus
formation despite appropriate anticoagulant therapy. Careful examination
with multiple modalities is often necessary for detecting and correctly
diagnosing an LA thrombus.