Global electrophysiology: Hybrid convergent ablation for persistent atrial fibrillation

There is a worldwide epidemic of atrial fibrillation (AF), a disorder which no longer is confined to the older population.1-3 In the Global Burden of Diseases, Injuries, and Risk Factors Study (the GBD 2010 Study), the estimated global prevalence of AF in 2010 was reported to be 33.5 million (20.9 million men and 12.6 million women), with significant increases in the estimated age-adjusted prevalence and incidence of AF.1 The prevalence of AF was reported to be highest in the United States, Europe, and Australia (1% in the adult population), and poorly estimated and possibly under-reported in the low-income and middle-income countries.1 Recent study on the global burden of AF and atrial flutter (AFL) and attributable risk factors reported China, United States, and India burdened with the highest of AF/AFL related deaths and disability-adjusted life years (DALYs), and pronounced increasing trends of incidence and prevalence in countries like the United Arab Emirates, Qatar, and Jordan.3 Overwhelming evidence directly links AF with increased mortality, and higher risk of myocardial infarction, heart failure, stroke, dementia, and chronic kidney disease. Many guidelines and scientific statements published over the last two decades provide ample evidence of beneficial outcomes including reduction in mortality, heart failure, and healthcare utilization from the rhythm control treatment strategy for AF.4-6 Treatment of patients with AF, however, continues to pose significant complexities and challenges. The field of nonpharmacological treatment, mostly comprised of catheter ablation of AF, has witnessed tremendous progress and growth in technology over the last two decades.4-7 In patients with paroxysmal AF, the goal and mainstay of the catheter ablation procedure is to accomplish total and durable electrical isolation of the PVs (PVI) from the left atrium (LA) using radiofrequency or cryo energy source.7 However, even with experienced hands, the treatment success at 12 months is not more than 65%–75%.8, 9 Success rate of catheter ablation is even worse in patients with persistent AF (PeAF) and long-standing persistent AF (L-PeAF) defined as AF lasting continuously for ≥7 days and ≥12 months, respectively. These patients who typically have more atrial myopathy from widespread fibrosis and scarring often require multiple ablation procedures. In such cases, besides PVI and targeting the cavotricuspid isthmus, the ablation strategy often comprises of targeting non-PV triggers, areas of automaticity, and arrhythmogenic micro re-entry clustered in the posterior wall of the LA with focal and linear ablation lesions. Since the abnormal arrhythmogenic foci and electrical breakthrough sites are often located at the epicardial sites, a hybrid approach integrating endocardial catheter ablation and minimally invasive surgical epicardial ablation has emerged to treat patients with PeAF and L-PeAF. In the multicenter randomized controlled CONVERGE (Convergence of Epicardial and Endocardial Ablation for the Treatment of Symptomatic Persistent AF) trial, hybrid convergent ablation (HCA) was found to have superior effectiveness, 21.5% absolute improvement off antiarrhythmic drugs (AADs), and 17.7% absolute improvement off new/increased dose of failed AADs, compared to endocardial catheter ablation at 12 months.10 Compared to catheter ablation, significant reduction in AF burden (risk ratio, 1.34) was also seen at 18 months with HCA.10 Furthermore, in the CONVERGE trial no cardiac perforations, atrioesophageal fistulas, or deaths were observed with HCA.10 Markedly improved long-term AF-free survival (87.6% at 1 year, 76.9% at 2 years, 70.4% at 3 years, and 59.3% at 4 years) with reduction in the AADs usage was demonstrated with HCA,11 so also significant improvement in the quality of life scores.12 Against the merits, HCA procedure does have some downsides and shortcomings. Even though the surgical component of the HCA procedure is technically defined as minimally invasive, it is surgery nonetheless. Catheter used for epicardial ablation also has limited reach especially to the uppermost and anterior aspect of the LA, and typically these areas need to be addressed with endocardial catheter ablation subsequently. A good number of HCA procedures have to be performed as staged procedures (typically endocardial catheter ablation performed approximately 6–12 weeks postepicardial ablation). If the HCA procedure is to be performed in its entirety as a single-sitting simultaneous procedure, it becomes a lengthy procedure. The patient therefore may not necessarily consent to the procedure in spite of extensive shared-decision making process given the attendant and default risks of the surgery as such. Repeated hospitalization and long procedure times add to the safety aspect. Other variables such as the health insurance authorization and clearance, hospital length of stay and financial reimbursement of the procedure may also be of important considerations. Additionally, from the HCA operators' standpoint, two different teams with different training in their respective fields have to work interdependently and with good understanding and co-ordination between them. It is against this background that "Convergent Ablation for Persistent Atrial Fibrillation: A United Kingdom Multi-Centre Perspective" by Mannakkara et al.; published in the current issue of the Journal of Cardiovascular Electrophysiology (JCE)13; needs to be viewed and discussed for the section of "Global Electrophysiology." A few points are worthy of discussion. The UK Convergent Ablation group started performing HCA procedure around 2012. With a marked increase in the procedure volume in the recent years, the UK group has reached over 500 procedures mark.13 Bearing in mind that the UK's publicly funded universal National Health Service (NHS) healthcare system with its limited resources has been under perpetual scrutiny, some specific points related to the UK Convergent Ablation program may be raised. Is it possible that given long waiting periods both to see local cardiac electrophysiologists trained to perform complex AF ablation, and to schedule eventual procedure date, the system might be preferentially diverting the patients for the HCA surgical part of the procedure, which may have shorter waiting time? Furthermore, it is not clear whether the NHS referral pathway system automatically refers every single patient with PeAF and L-PeAF for HCA. If so, apart from the obvious patient selection bias for HCA which may skew the outcome and performance data, the question then to ask is whether the clinical presentation of PeAF or L-PeAF per se would justify subjecting the patients to the invasiveness of HCA procedure. Given the current state of financially drained NHS, I sincerely doubt that the UK Convergent Ablation group would routinely use noninvasive multimodality imaging including the cardiac MRI scanning and electrophysiology methodology to assess the density of atrial scar and mechanical function in their patient selection process. How should overtreatment by empirical surgery just to isolate the posterior LA wall be avoided in any patients with AF? Many patients with PeAF and L-PeAF do get treated successfully and safely with endocardial catheter ablation alone using conventional radiofrequency low power of 20–40 W for a relatively long duration (20–40 s) (LPLD), or high power (50 W or higher) for short duration of 5–10 s (HPSD). One can also perform radiofrequency ablation even at a very high power of 90 W for short amount of time (4 s) (vHPSD) with a recently introduced QDOT MICRO Catheter (Biosense Webster). Besides thermal ablation including cryoablation, many centers are now quickly switching to nonthermal pulsed field ablation (PFA), efficacy, and safety of which have been evaluated in large studies that enabled regulatory approval of PFA in the United States and European countries.14, 15 Appropriate evaluation of efficacy, safety, and long-term clinical outcomes of HCA against these modalities of treatment of AF, with and without concomitant LA appendage exclusion for stroke prevention in both arms of treatment is needed through clinical trials. In conclusion, the UK Convergent Ablation group's multifaceted perspective on HCA presented herein, may serve as a reference and a model in the treatment of AF especially PeAF or L-PeAF to many electrophysiologists around the globe. The data that support the findings of this study are available from the corresponding author upon reasonable request.