METHODS
Study
patients
One hundred fifty-eight patients were included in the study. These
patients were drawn from a pool of 195 consecutive patients (152 men, 42
women; aged 64 ± 10 years) who had undergone balloon-based ablation
(HBA, n=103; CBA, n=92) for PerAF at Dokkyo Medical University Saitama
Medical Center or Nihon University Itabashi Hospital between June 2015
and January 2019. PerAF was defined as AF lasting ≥7 days but
<12 months, and no patient with long-standing PerAF (AF
lasting >12 months) was included. So that a study comparing
HBA and CBA could be performed. the total patients were assigned
propensity scores, which accounted for age, sex, body mass index,
CHA2DS2-VASc score, left atrial diameter
(LAD), and left ventricular ejection fraction (LVEF). Nearest neighbor
matching within a 0.2 caliper width and 1:1 matching ratio issued in 2
study groups of 79 patients each.
The institutional review boards
at Dokkyo Medical University Saitama Medical Center Bioethics Committee
and Nihon University Hospital Ethics Committee approved the collection
and review of these data.
Preparation for
Ablation
For all patients, antiarrhythmic drugs (AADs) were discontinued for at
least 5 half-lives prior to the ablation procedure. Conscious sedation
was achieved with dexmedetomidine, propofol, and fentanyl. Vascular
access was obtained, a single transseptal puncture guided by
intra-cardiac ultrasound, was performed, and intravenous heparin was
administered to maintain an activated clotting time of >300
seconds. Three-dimensional maps of the LA and 4 PVs were created with
the NavX system (Abbott Laboratories, Abbott Park, IL).
HBA
HBA was performed with the SATAKE HotBalloon ablation system (Toray
Industries, Inc., Tokyo, Japan) during AF rhythm, as previously
described.1,4For PV occlusion, the balloon was inflated to 26–33 mm in diameter with
10–20 mL of contrast medium diluted 1:2 with saline. Once optimal PV
occlusion, assessed by contrast angiography, was achieved, a 1.8-MHz RF
current was applied between the coil electrode inside the balloon and 4
cutaneous electrode patches on the patient’s back to produce
capacitive-type balloon heating. The target internal balloon temperature
(70ºC or 73ºC for the left superior PV [LSPV] and 70ºC for the other
PVs) was maintained by delivery of vibratory waves through the catheter
shaft lumen into the balloon to agitate the fluid inside. Because of the
relatively high incidence of PV stenosis previously
reported,4 we performed
the procedure via antral approach to avoid intra-PV ablation and thus
prevent chronic-phase complications. The balloon was positioned at the
PV ostium (not inside the PV) by adjustment of the injection volume
(10–12 cc) so the balloon would completely appose the antrum and
occlude the PV. The same protocol was followed for each patient, i.e.,
delivery of a single “shot” of thermal energy to each superior and
inferior PV. For wide antral ablation, bilateral upper posterior
wall-targeted HBA was performed after the superior PV applications. The
balloon was further inflated (14–16 cc) and advanced toward the
posterior LA wall or roof at the superior PV antrum level (in close
proximity to the superior PV isolation areas) by clockwise or
counterclockwise sheath rotation. Subsequently, thermal energy was
delivered in a single shot to the right PV carina region (Figure 1).
Regardless of the presence or absence of residual conduction, no further
HBA was performed.
To prevent phrenic nerve injury, diaphragmatic pacing was performed from
electrodes placed along the lateral wall of the superior vena cava. To
avoid esophageal damage, esophageal temperature monitoring was performed
with a steerable esophageal temperature probe (Esophastar, Japan
Lifeline, Tokyo, Japan). If the temperature exceeded 39°C, water was
injected to cool the
esophagus.1,4,5
CBA
CBA was performed with a second-generation cryoballoon system (Arctic
Front Advance [ARC-Adv-CB], Medtronic, Minneapolis, MN), as
previously described.6 A
28-mm cryoballoon, used in conjunction with an inner lumen mapping
catheter (Achieve, Medtronic), was inflated and advanced to each PV
orifice. Once optimal PV
occlusion, assessed by contrast angiography, was achieved, cryothermal
energy was applied in a single shot to the LSPV for 180–240 seconds and
to the other PVs for 180 seconds each (Figure 1). As in HBA,
diaphragmatic pacing, and esophageal temperature were monitored.
Cryothermal energy application was abandoned when the esophageal
temperature reached <20°C.
Voltage mapping and measurements of
the isolated surface
area
If the patient was in AF rhythm after ablation, cardioversion was
performed. High-density bipolar voltage mapping was performed during
sinus rhythm. Bipolar signals were acquired with a 20-pole circular
catheter (A Focus-II, Abbott). If necessary, coronary pacing was used to
determine the local electrocardiogram. Exit block was confirmed by
sequential pacing from the circular catheter. If and where residual PV
potentials, manifesting as spontaneous PV reconnections, were seen,
touch-up RF ablation was performed at those sites with a 4-mm-tip
irrigation catheter (FlexAbility, Abbott). RF energy was applied
point-by-point at a maximum power output of 25–35 W, and the
temperature was set to a maximum of 43°C.
After confirmation of complete PVI, as shown in Figure 2, the isolated
antral surface area (IASA) and posterior LA wall surface area were
measured by means of the NavX system. The PV ostium was identified as
the point of maximal inflection between the PV wall and LA wall, and the
PV antrum was defined as the region proximal to the PV ostium. An IASA
was defined as an area on the NavX map between an area of low voltage
(<0.2 mV) and the corresponding PV ostium (Figure
2),7 and the sum of the
right-sided and left-sided IASAs was taken as the total IASA. The
posterior LA wall surface area was defined as the area formed by the
superior and inferior margins of the LA and the section of posterior LA
wall with bipolar voltage amplitudes of >0.2 mV. The ratio
of the total IASA, excluding the PVs, to the sum of the IASA and PWSA
was taken as the isolated surface area (ISA). The ISA (%) was
calculated as follows: total IASA [cm²] / (total IASA [cm²] +
posterior LA wall surface area [pLAWSA] [cm²]) ×100.
Post-ablation
follow-up
On the day after the ablation procedure, all antiarrhythmic drugs
previously prescribed were resumed, at the individual operator’s
discretion. Follow-up was performed at the hospitals’ respective
outpatient clinics, where physical examination and 12-lead
electrocardiography were performed at 2 weeks, and every 1 months
thereafter. Twenty-four-hour Holter recordings were obtained at 1,3, and
6 months and every 3 months thereafter. Any symptomatic or documented
atrial arrhythmia of ≥30 seconds after a 3-month blanking period was
taken as a recurrence of the AF.
Statistical
analysis
Data are shown as mean ± SD or median (25th,
75th percentile) values. Patient’s baseline clinical,
echocardiographic, and electrophysiologic characteristics were compared
between the 2 propensity score-matched groups. Procedure-related details
and complications were also compared between the 2 groups. Differences
were analyzed by Student t -test, Mann-Whitney U -test, or
χ2 test, as appropriate. All patients were followed up
for at least 12 months, Kaplan-Meier curves for the freedom from
AF/atrial tachycardia (AT) were generated, and between-group differences
were analyzed by log-rank test. Predictors of AF recurrence were
performed using Cox proportional hazards regression models. All
statistical analyses were performed with JMP 13.2.1 software (SAS
Institute, Cary, NC), and P < 0.05 was considered
significant.