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.