Our Road to Zero Radiation Catheter Ablation in Pediatric and Congenital Heart Disease

Introduction

Fluoroscopy has long been a standard part of catheter ablation procedures in children. In the early to mid 1990s, the Pediatric Radiofrequency Ablation Registry showed that fluoro times of 1-2 hours were common,¹ and improved only modestly with personal experience² and the passage of time,³ keeping in mind that in this era, the delivered doses were extremely high (eg, air kerma 6 to 49 mGy per minute⁴) and radiation exposure has particular relevance to children with long lifespans for neoplasm to develop.^5,6

The development of three-dimensional electroanatomic mapping (EAM) systems began to change the landscape by the early 2000s,⁷ but average fluoro time remained above 30 minutes in the large multicenter registry of that era,⁸ despite contemporaneous demonstration of the feasibility of zero radiation ablation (of right-sided substrates, in 2002).⁹ Only a few reports of zero radiation ablation emerged over the remainder of the decade.^10-12 In the early to mid 2010s, reports on pediatric ablation frequently described significant radiation use^13-20 with fluoro times averaging 5 to 30 minutes (and air kerma, when reported, averaging 13 to 250 mGy), although other reports^21-24 documented average fluoro times under 5 minutes (often with zero radiation procedures in a subset of patients), with several centers reporting uniform achievement of zero radiation or near-zero radiation (eg, fluoro times averaging 0.1 minute) in the mid to late 2010s.^25-29 

Although not previously reported, our experience is in the latter group, with a zero radiation approach for all pediatric/congenital ablation in the past several years (Figure 1).

Practice in Times of Change 

My training in catheter ablation occurred during this period of rapid technological evolution. Practice patterns were similar during my pediatric cardiology fellowship at the University of Minnesota in 2009-2012 and pediatric electrophysiology fellowship at the University of Toronto / Hospital for Sick Children in 2012-2013; at that time, both sites routinely employed EAM, but utilized fluoroscopy for confirmation of vascular access, diagnostic catheter placement, long sheath placement, transseptal puncture, and intermittently during mapping/ablation, particularly when near to the normal conduction system.

In 2013, during the Heart Rhythm Society’s Scientific Sessions, I attended a brief but impactful talk by Dr. Robert Pass (now at Mount Sinai, New York) about ALARA (as low as reasonably achievable) principles in pediatric ablation. In addition to highlighting the importance of radiation reduction, Dr. Pass demonstrated EnSite (Abbott)-guided diagnostic catheter placement and coronary sinus cannulation. 

Wanting to minimize radiation exposure, and noting that initial catheter placement comprised the most fluoro use in my existing practice, I chose to try EnSite-guided catheter placement, which was not too challenging to learn (Figures 2 and 3). I adopted it universally upon entering practice in 2013, and never looked back. Over subsequent years, I explored different techniques to eliminate fluoroscopy from various aspects of the ablation procedure (Table 1).

We have also previously used a ceiling-mounted radiation protection system (Zero-Gravity, BIOTRONIK). At the time, I was pleased to be able to abandon my lead apron but still have easy access to fluoroscopy for select tasks (ie, transseptal puncture). However, each use of this system reminded me that while I was avoiding the potential orthopedic consequences of lead apron use, only a true zero radiation technique shares these benefits with the rest of the team. 

Data Analysis

Methods

To characterize our progress, we analyzed 5 years of consecutive pediatric/congenital ablations by a single operator (Figure 1). The effect of the initial switch to EAM-guided catheter placement in 2013 is not captured, as data from prior to 2015 were not readily accessible due to a change in our medical records software.

The time period was divided into 3 eras depending on the location that most cases were performed. In era 1, we were based in an older Philips biplane lab with equipment settings configured to adult EP protocols (with Zero-Gravity available but rarely used). In era 2, we were based in a new GE biplane lab with pediatric protocols. In era 3, we were based in a new Siemens biplane lab with pediatric ultra-low-dose protocols (with Zero-Gravity and a dedicated high-end ultrasound machine for vascular access). Occasional cases were performed in other locations for scheduling reasons or when Stereotaxis was desired. 

Results

After stepwise practice changes (Figure 1), we have for the past 2 years provided zero radiation ablation for routine pediatric supraventricular substrates (largely using EnSite, and occasionally with the Rhythmia Mapping System [Boston Scientific]) and most complex congenital atrial arrhythmias (same), and near-zero radiation ablation for ventricular substrates (using CARTO [Biosense Webster, Inc.] and Stereotaxis, which benefit from momentary fluoroscopy for initial calibration).

Although not highlighted in this report, we have also worked to reduce the radiation dose per minute of fluoroscopy per ALARA principles by adjusting beam settings and frame rate, and optimizing detector positioning and collimation. This no longer affects our ablations, but the resulting benefits translated to device cases, where we see an average of 2 mGy per case and generally accumulate exposure at about 0.2-0.3 mGy per minute of fluoro time (a 99% reduction from this 1996 study⁴).

Conclusions

Radiation use during catheter ablation has important consequences for patients (particularly in children who have a long period of stochastic risk, and complex congenital heart disease patients who frequently have significant exposure from other procedures and hospitalizations) as well as medical personnel.

Some procedural steps can be easily converted to zero radiation, such as vascular access and catheter/sheath placement, whereas others are somewhat more difficult (eg, transseptal puncture, baffle puncture, and managing sheath-catheter interactions, especially with deflectable sheaths). However, the challenges should not be daunting, particularly in comparison to the other new procedural skills we have tackled over the years.

Importantly, even when the goal is not complete elimination of radiation use, substantial benefits can be realized by efforts to reduce or eliminate fluoroscopy from even a few tasks. 

Additionally, careful attention to ALARA principles can dramatically reduce the true radiation dose, even when fluoroscopy continues to be used. These gains are particularly easy to achieve.

I would also mention that while ICE is frequently cited as a key tool for zero radiation ablation in the adult literature,³⁰ it has vascular access implications that are important for smaller patients (as well as cost implications). I do find ICE valuable for complex anatomy (eg, aortic cusp and papillary muscle foci, congenital heart disease) and for transseptal puncture in older children or when TEE is not optimal. But personally, I think that EAM alone is sufficient for the majority of routine pediatric ablations targeting right-sided substrates or when a patent foramen ovale permits left-sided access. 

Exclusive video content available for this article: 

Video 1: Zero radiation CS catheter placement. 

Video 2: Zero radiation RV catheter placement. 

Video 3: Zero radiation His catheter placement.

Acknowledgements: I would like to thank the excellent local teams from Abbott, Biosense Webster, and Boston Scientific, all of whom have been critical to facilitating zero radiation procedures with their respective mapping systems. 

Disclosures: Dr. Vinocur has no conflicts of interest to report regarding the content herein. 

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