Is a ring of gold what we waited for to treat atrial fibrillation?

This editorial refers to ‘Paroxysmal and persistent AF ablation outcomes with the PVAC GOLD duty cycled phased RF ablation catheter: quality of life and 12-month efficacy results from the GOLD AF registry’ by L. Boersma et al., on pages 888--896.

The multielectrode circular phased pulmonary vein ablation catheter (PVAC) was introduced as a consequence of pulmonary vein isolation (PVI) becoming a routine procedure for the treatment of atrial fibrillation (AF) and to provide a safe and efficient single-shot technique along with the increasing demand for PVI. While the cryoballoon catheter represents the best evaluated single-shot device for PVI, the role of PVAC remains less clarified. Even though the first generation PVAC catheter showed results comparable to conventional techniques, concerns were raised about higher incidence of cerebral embolism with this method.^1–3 Therefore, the 2^nd generation, the PVAC GOLD catheter, was designed for better thermodynamic control and the power delivery algorithm was optimized. While the PVAC GOLD catheter seems to enable faster PVI compared to PVAC,⁴ conflicting results exist from smaller studies about the safety regarding cerebral embolisms and asymptomatic cerebral embolisms (ACE).^5,6

In this context, the current study by Boersma et al. offers additional valuable information by reporting data from the multinational Gold AF Registry.⁷ From 2015 to 2017, 40 centres prospectively enrolled consecutive patients treated for AF with the PVAC GOLD catheter. Including observational data from 1054 patients, the authors report outcomes on 12-month freedom from AF and quality-of-life (QoL) assessment as well as safety and procedural parameters. Patients were followed for 12 months. The first major finding is a low periprocedural complication rate of 2.5%, including clinical evident ischaemic strokes in only 0.3% of patients. These results are encouraging and in line with complication rates observed with PVI done by point-by-point radiofrequency ablation (RFA) or cryoballoon ablation. Acute procedural success was achieved in 96% of patients with an average total procedure time of 107 min. Twelve-month freedom from AF, after a 90-day blanking period, was reported to be 78% based on clinical evaluation by local standards and improvements in QoL as well as the European Heart Rhythm Association (EHRA) symptom scores were impressive.

Compared to previous studies on PVAC GOLD catheters, the current study has several strengths. It was conducted in 14 countries at 40 different centres and included a larger number of patients with different types of AF. This indicates, that implementation of the PVAC GOLD is possible in a broader setting.

Several issues however need to be considered while interpreting these data. One of the main conclusions from this study is the high success rates achieved with the PVAC GOLD. A major drawback in this regard is the lack of standardized follow-up. The population included, mainly consists of relatively young low-risk patients with limited comorbidity and 70% with paroxysmal AF. A group of patients where a high success rate with PVI should be expected. No information is provided about the frequency and type of arrhythmia monitoring performed. Recurrence was documented by Holter monitor recording in only 23% of cases with recurrent arrhythmia, raising concerns that a significant number of asymptomatic cases is missed. Atrial flutter was detected in only 0.4% of cases with recurrence, further supporting concerns about the sensitivity of arrhythmia detection. Limited information is provided about the clinical setting of follow-up, but apparently in most cases this was done by telephone, seriously compromising the ability to detect ongoing AF. The reported rate of recurrent AF using the PVAC GOLD catheter thus must be considered merely a very conservative estimate.

Based upon the FIRE AND ICE trial,⁸ we know that both efficacy and safety are similar between point-by-point RFA and cryoballoon ablation while doing PVI. As an observational study with no control group, the present study does not tell us whether using the PVAC GOLD catheter is worse, better or similar to these two methods. The study reported a promising improvement in QoL scores in around 90% of patients. However, results from only 2/3 (658) of patients included in the study seem to be included in the analysis, and of those 70% where acquired by telephone. Is validity of QoL assessment by telephone similar to the situation where patients fill in these forms themselves?

The authors also seek to answer the important question, whether PVI using the PVAC GOLD is safe, in respect to not creating cerebral embolisms. It’s reassuring that only 3 strokes (0.3%) occurred. However, as the clinical evaluation, including the neurocognitive evaluation, was done according to local standard-of-care and not described in the manuscript, it’s difficult to appraise the validity of this finding. More worrying is the reported procedural activated clotting time (ACT) levels, ranging from 274 to 357 s, indicating that only a minority of procedures were done with ACT levels ≥350 s. Studies able to demonstrate low incidence of ischaemic strokes and ACE with the PVAC, had predefined protocols requiring ACT levels ≥350 s.^5,9 In 54% of cases, anticoagulation was discontinued prior to the procedure, but no further details are provided including when it was resumed. In general, as specific procedural requirements were not defined by the protocol, reporting of practices used in the patients included would be appreciated, as diverse results regarding ACE have been attributed to procedural practice rather than to the PVAC technology itself.^5,6,9 Finally, this manuscript reports data from a post-marketing database owned by the manufacturer, and apparently, the manufacturer was involved in producing the manuscript also.

The present study adds valuable information to the growing evidence about use of the PVAC GOLD catheter in a clinical setting. However, using the PVAC GOLD still cannot be considered equivalent to point-by-point RFA or cryoballoon ablation for PVI, as our knowledge about safety and efficacy of this technology still is limited. To answer these questions a well-powered, multi-centre, randomized trial is needed, comparing this methodology to the standard of today. In such a trial, the procedural conditions should be predefined, follow-up includes quantification of AF burden by regular rhythm monitoring and uniform neurocognitive testing included. Even though the clinical importance of ACE still is debated, standardized magnetic resonance imaging of ACE as recently suggested⁶ should be included in such a study as the previous generation PVAC catheter specifically is suspected to cause embolization.

Conflict of interest: J.M.N. reports grants from Biosense Webster. J.C.N. reports grants from the Novo Nordisk Foundation (NNF16OC0018658).

The opinions expressed in this article are not necessarily those of the Editors of Europace or of the European Society of Cardiology.

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