4.1 Main findings
This is the first and only single-centre, multi-operator large real-world registry evaluating procedural outcomes and safety using the second-generation PVAC GOLD in over 1000 patients. The present study shows a high rate of acute successful PVI, while retaining swift procedure times and a desirable safety profile for paroxysmal, persistent and long-standing persistent AF patients. Furthermore, additional CFAE ablations in the left atrium with either PVAC GOLD or MASC and MAAC did not affect the safety outcomes.
4.2 Acute success
Acute success was attained in 97.5% of patients and 99% of PVs, similar to isolation rates observed with the first-generation PVAC [
5‐
7]. These high rates of procedural success are consistent with clinical trials investigating the latest-generation cryoballoon or conventional RF ablation, showing acute success rates of 97 up to 100% of cases [
8‐
11]. Large registries and multinational surveys assessing irrigated RF and cryoballoon ablation resembling a more real-world population and show lower success rates (83–95%) [
12‐
14]. Therefore, the results we found are reassuring and confirm procedural efficacy for paroxysmal and persistent AF patients. Durable PVI and long-term arrhythmia-free survival was not assessed in this paper and further research is needed to address these topics.
4.3 Procedural characteristics
The PVAC GOLD system encompasses a simple and efficacious technique to achieve PVI, leading to favourable procedural characteristics. The median procedure time was less than 90 min in the PVI-only groups and 100 min in the PersAF-PVI + CFAE group. Likewise, fluoroscopy time and ablation time were short, confirming the swift procedural characteristics previously reported in smaller trials and registries [
6,
7,
15]. Compared with the reported procedural characteristics of conventional point-by-point ablation [
9,
10,
12,
13,
16] and to a lesser extent to cryoballoon ablation [
8,
10,
11,
13], we found PVAC GOLD to have considerably shorter procedure times, fluoroscopy times and ablation times. These findings are in agreement with a meta-analysis performed by Kabunga et al., who compared phased RF, irrigated RF and cryoballoon [
17].
4.4 Safety outcomes
Safety remains an important topic in AF ablation. Although regularly reported, heterogeneity in screening methods and the definitions used to include and classify complications remains problematic. Reported major safety outcomes widely vary between 1.4 and 16% and focus mainly on paroxysmal AF [
6‐
8,
13,
15,
16,
18]. We reported outcomes according to the 2017 consensus statement to support uniform data presentation. Procedure-related complications were seen in 4.2% of patients and major complications were seen in 1.87% of patients, of which only 0.39% left sequelae. Although 3 months of follow-up was assessed to determine procedural safety outcomes, late-onset or less clinically overt complications might be underreported in this registry.
We found no differences in safety outcomes between patients with paroxysmal and non-paroxysmal AF. Furthermore, additional CFAE ablations with PVAC GOLD or MASC and MAAC in the left atrium did not impact safety outcomes. Previous, mostly small studies on the second-generation PVAC GOLD catheter reported major complications ranging from 0 to 6.5% [
6‐
8,
15]. More recent and larger studies by Spitzer et al. and De Greef et al. showed more comparable major complication rates below 2% [
15,
18].
Compared with important landmark trials like FIRE and ICE, CABANA and STAR-AF [
9,
10,
19], we observed lower rates of major complications. A large Italian registry including 2167 patients from 29 centres using open-irrigated catheters showed similar complication rates of 3.7% and 0.20% complications with permanent sequelae [
16]. Similar results were found in a German registry for paroxysmal AF, including 3775 patients who underwent cryoballoon or RF ablation and reported 4.6% major adverse events in both cryoballoon and RF ablation [
8].
Major complication rates reported on PVAC GOLD seem to be on the lower end of the spectrum. An explanation might be the low incidence of phrenic nerve palsy and cardiac tamponade.
In contrast to cryoballoon ablation procedures, phrenic nerve palsy is rare and occurred in only a single patient. Of interest, when ablation is performed and the phrenic nerve is near, typically capture of the phrenic with rapid oscillation of the right hemi-diaphragm is both visible and tangible for the operator. This early warning sign allowing immediate discontinuation of energy delivery, as well as the awareness to stay outside the tubular part of the PV may be an explanation for the low rate of phrenic nerve palsies.
Compared with single-shot devices, conventional point-by-point RF ablation may cause more cardiac tamponades and pericardial effusions [
7,
8,
10,
18]. The over-the-wire design and the use of a circular array might help distribute pressure over a larger area, thereby preventing stress on small areas and risk of steam pops and perforations as is evident from the very low number of tamponade which were usually related to the transseptal puncture.
Using PVAC GOLD, we observed a low stroke/TIA rate (0.39%), which is in line with or even lower than in other large AF ablation trials such as STAR-AF (0.53%), FIRE and ICE (0.5% radiofrequency, 0.5% cryoballoon) and CABANA (0.3%) and a smaller single-centre report by Spitzer et al. on 384 patients treated using PVAC GOLD (0.52%) [
9,
10,
15,
19]. This is reassuring in the sense that using multi-electrode catheters with non-irrigated phased RF energy appears to be as safe as other technologies and does not lead to clinical neurological sequelae. Other factors such as our strategy of uninterrupted anticoagulation have also been shown to reduce the occurrence TIA and stroke, even though it would not be effective against the formation of thermally induced coagulum and subsequent stroke, TIA or ACE. The main reasons for the design change of PVAC platinum with 10 electrodes to PVAC GOLD with 9 electrodes however was the concern for a higher asymptomatic cerebral embolism rate [
3,
4]. Extensive studies in animal models showed that it was the interaction between electrodes 1 and 10 on the catheter that led to overheating with gas and particle formation, which caused temporary micro-emboli in the brain that completely resolved shortly after the procedure without causing any neurological deficit. Avoiding simultaneous ablation on electrodes 1 and 10 resolved the ACE problems (ERASE trial), which led to the design of a 9-electrode array with gold electrodes for better heat dissipation with a confirmed extremely low ACE rate (PRECISION GOLD trial). Given these reassuring studies that were in part done at our own centre, DW-MRI was not part of our regular peri-procedural assessment of safety as it is a burden to patients, as well as a logistical challenge that does not seem cost-effective as it has no consequence for the patient. The issue of ACE lesions and their clinical significance after any type of ablation however remains in part unresolved, as is the fact that some operators achieve low rates (PRECISION GOLD De Greef et al. 2.1% multicentre trial with strict procedural guidance, core lab strict MRI assessment) while others do not (Keçe et al., 23%, single-centre experience) [
3,
20].
4.5 CFAE ablations
CFAE ablations were safely performed in half of the patients with persistent AF and in 77% of the patients with long-standing persistent AF. CFAE ablations did significantly lengthen the procedure and required additional fluoroscopy time, but the major complication rate and non-major complication rate were still low and equal to the PVI-only groups. This was also reported by Chen et al., who performed a meta-analysis on efficacy and safety of adjunctive substrate modification, as well as results found in the STAR-AF trial [
9,
21]. Despite a safe and successful procedure, the effect of CFAE ablations as a first-line treatment for atrial fibrillation on arrhythmia-free survival remains controversial [
9].
4.6 Limitations
The current study was designed to present daily practice data on acute success and safety in different patient groups and treatment strategies using multi-electrode phased RF ablation. The choice for PVAC GOLD was not randomized and additional substrate modification was performed at the discretion of the operator. During the inclusion period, 96% of first-time AF ablations were performed using PVAC GOLD, depicting a true all-comers population. Consequently, no suitable control group with comparable standard of care and follow-up could be selected. Head-to-head comparison between the different groups must be interpreted with caution, as the patients within groups are not interchangeable and encompass different risk factors. Despite strong differences in patient characteristics, all groups showed similar and reassuring acute success rates and a low number of safety outcomes. Multicentre randomized clinical trials are the gold standard for comparison, but due to the low rate of incomplete PVI and safety outcomes as well as the rapid evolution of available techniques and alterations in standard of care, such trials will be unfeasible. Therefore, uniform reporting in large registries are of important value to appreciate ablation technologies. In our registry, no variables showed > 5% missing values and missings appeared to be at random. The primary outcome variables did not contain any missing values. While acute success rates are reassuring, outcomes on long-term arrhythmia-free survival are warranted.