Introduction
Atrial tachycardia(AT) occurring from the right atrial appendage(RAA) is
relatively uncommon, with a proportion of approximately 8% among all
focal AT patients1. Nevertheless, right atrial
appendage tachycardia(RAAT) is not easily terminated and is commonly
associated with tachycardiomyopathy, whihe the catheter ablation of RAAT
is complicated by its anatomic characteristics. Hereby, we presented a
case of incessant AT which was termintaed by pulse field ablation(PFA)
using circular PFA catheter.
Case presentation
A 60-year-old male patient complained with persistent palpitations and
chest tightness for two months. He was prescribed with metoprolol after
being diagnosed with “inappropriate sinus tachycardia” in other
hospitals. However, it did not work and he was admitted to our
department for further treatment. The 24-hour Holter
electrocardiogram(ECG) showed incessant AT, presenting with mean heart
rate of 124bpm. As shown in the baseline 12-lead ECG(Figure1A),
low-amplitude positive P-wave can be observed in leads I, II, and avF,
while negative P wave in avR and V1 leads. Accordingly, it indicated
that AT originating from RAA should be taken into consideration. After
informed consent was obtained, the tachycardia activation mapping using
three-dimensional electroanatomic reconstruction system(CARTO, Biosense
Webster) and a conventional 3.5 mm tip steerable catheter (NaviStar,
Biosense Webster, CA, USA) confirmed that the AT originated from the tip
of RAA. A conventional radio frequency ablation attempt (power: 30 W,
target temperature: 43◦C, irrigationflow rate: 17 mL/min) was performed
but failed to eliminate AT. Given that the potential risk such as
cardiac tamponade and invalid conventional ablation of RAA, we decided
to use PFA catheter for second ablation after thorough communication
with the patient.
After signing the informed consent form, the second ablation procedure
was performed using the circular mapping&PFA catheter(Jinjiang
Electronic Medical Equipment Co., Ltd. PRC). Both the right atrium and
the RAA were reconstructed. The AT activation mapping was in agreement
with RAA origin(Figure 2). During the mapping process in the RAA, the AT
could terminate spontaneously and sinus rhythm was restored transiently.
Moreover, the earliest activation point of the focal RAA-originated AT
was away from sinus node mapped during sinus rhythm. Four electrodes of
the circular mapping&PFA catheter, which located at the earliest
activation site, were selected for PFA using 1800Volts, 480μs. The AT
was terminated at the first attempts(Figure 3). A total of three
overlapping applications were delivered. No AT can be induced by burst
atrial pacing or isoproterenol administration. The substrate remapping
after ablation showed that only a small area of low voltage at the tip
of RAA was observed. No complications occurred. Acute procedural success
was achieved as shown in the post-ablation 12-lead ECG(Figure 1B). At
one-month follow-up, the patient was free of ATs and atrial premature
beats.
Discussion
The focal AT occurring from the RAA is relatively uncommon, while the
catheter ablation is complicated by the anatomic characteristics. The
thin nature of RAA raises the risk of cardiac perforation during
catheter ablation, especially in the apex of RAA. Traditional catheter
ablation using radiofrequecy energy is always difficult to achieve a
target temperature due to the fact that the pectinate component of the
RAA does not allow energy infiltration into the AT focus. Thus,
therapeutic options for ablation within RAA has been extensively
investigated. Previous study suggested that irridated-tip catheter might
be helpful for these patients2. The combination of
catheter ablation and video-assisted thoracoscopic atrial appendectomy
has also be considered effective to manage focal AT from
RAA3. Compared to this more invasive approach,
cryoballoon ablation has been found to be an alternative therapeutic
strategy that might obviate unnecessary and harmful radiofrequency
ablative attempts4, 5. However, it should be noted
that the tip pf the cryoballoon is rigid and can lead to more
extensively inaccurate lesion. Recently, Lukas Urbanek et al reported a
case of an incessant AT arising from RAA that successfully treated with
pulsed field ablation using four electrodes of 31-mm FARAWAVE
catheter6.
In this case, circular PFA catheter was firstly used for mapping and
ablation of focal AT from RAA. It has been shown to be safe and
successfully eliminate AT at the first attempts within 3s. PFA has been
recently introduced for PV isolation in atrial fibrillation
patients7. It is a nonthermal ablative modality which
can destabilize cell membranes and preserve extracelluar matrix by
forming irreversible nanoscale pores and leakage of cell contents,
culminating in cell death. Notably, specific characteristic threshold
field strengths could be observed in various tissues, with the lowest
threshold values in cardiomyocytes. This myocardial specificity could
potentially limit collateral damage of adjacent tissue and avoid
post-ablation complications. PFA within RAA can reduce the risk of
pericardial tamponade caused by atrial appendage rupture due to RFA or
cryoballoon ablation. In addition, a deeper ablation lesion can be
achieved by PFA than traditional energy, which can lead to effective
elimination of deep lesions in the pectinate muscle of RAA. The ablation
procedure of PFA is often accomplished within milliseconds or even
shorter, which greatly shortens the operation time and further reduces
the risk of complications. Thus, for ablation of special structures such
as the atrial appendage, PFA seems safer and more effective than RFA or
cryoablation. It can be concluded that PFA might be an alternative
strategy for ablation of atrial arrhythmia originating from the atrial
appendage. Further research is needed to confirm our findings.