In this series, zero-fluoroscopic approach was achieved in 94% of cases with the use of the novel integrated impedance and magnetic-field-based electroanatomical mapping system. We reported a significant reduction in fluoroscopy doses almost to zero in this population, without compromising procedure times, success rates, or complications.

This is the first series with the novel EnSite Precision^™ EAM system, which illustrated the feasibility, safety, and benefits of use of the to achieve a fully zero-fluoroscopic approach in the vast majority of SVT cases. In our experience, the approach was feasible in all cases, where right atrial access was required. In three patients, fluoroscopy was required only to aid trans-septal puncture. However, it must be noted that we reported on the first consecutive 50 cases we have performed using this technique, which involved the learning curve, that might have had a bias on the trans-septal punctures. With the increasing operator experience following the learning curve and the use of ICE, we managed to overcome that limitation as well. Alternatively, trans-oesophageal echocardiography might be helpful in those cases to facilitate the trans-septal puncture. Thus, zero-fluoroscopy approach can be feasible for SVTs that require left atrial access as well.

In our cohort, significantly less ablation was required to achieve cavo-tricuspid isthmus block in typical atrial flutter, using the novel approach. Minimizing ablation time for these cases might have the potential to reduce ablation-related complications.

The risk of radiation exposure in cardiology is well recognized for patients and as an occupational hazard for laboratory staff [6]. Medical exposure to radiation has increased in line with advancements in diagnostic imaging and is now the most significant manmade source of radiation [7]. In 2006, medical exposure constituted nearly half of the total radiation exposure of the US population from all sources [8]. Cardiology procedures account for about 40% of the entire cumulative effective radiation dose to the US population from all medical sources, excluding radiotherapy and any attempt to reduce exposure is essential [1, 9‐11].

Radiation increases the lifetime risk of certain carcinomas, via stochastic and non-stochastic (deterministic) effects. The latent period between radiation exposure and cancer presentation confers that younger patients are more susceptible to this risk (as in elderly patients, this latent period is more likely to exceed the patient’s life expectancy). This is important in electrophysiology as many patients undergoing SVT ablation are relatively young with few co-morbidities, and SVT ablation is common also in the paediatric population [12].

It is not just patients who are at risk, but operators too; a growing body of evidence exists implicating radiation exposure in vascular disease [13], cognitive impairment [14], and tumours of the brain and neck [15] in physicians who perform fluoroscopic-guided interventional procedures. Furthermore, wearing lead protection has been associated with fatigue and orthopadic complaints for laboratory staff [16], although lead aprons block just about one-third of scattered radiation [17]. Given these well-recognized hazards, it is vitally important that zero- or near-zero-fluoroscopic approaches in EP are explored and refined, to minimise risks. These are especially important in high-risk populations, including children, pregnant women, and women with child-bearing potential [18, 19].

The benefits of using 3D electroanatomic mapping (EAM) systems to minimise radiation in the electrophysiology lab have been documented in several recent reports of minimal and zero-fluoroscopy approaches during SVT ablation [5]. Current systems in use include the EnSite NavX, the MediGuide (Abbott Inc, both), the CARTO 3 (Biosense Webster, Diamond Bar, CA, USA), and the Rhythmia (Boston Scientific, San Jose, CA, USA). The CARTO-UNIVU^™ Module (Biosense Webster, Diamond Bar, CA, USA) merges real-time EAMs with pre-acquired fluoroscopy images to help reduce overall radiation use. These mapping systems mainly rely on combinations of magnetic location technology with impedance-based data for catheter localization.

Current evidence supports the assumption that 3D-EAM systems reduce fluoroscopy exposure without affecting procedure safety and outcomes [5]. Success rates using these approaches are variable, but generally are high (70–95%) for the diagnosis and ablation of SVTs [5] (where success is defined as complete zero-fluoroscopy during the procedure). Success rates are certainly depending on the type of the procedure, operator experience and patient selection. The success rates for complete zero-fluoroscopy were reported around 80% for AVNRT in an early publication [20] and 90% for typical atrial flutter in a recent one [21]; it was almost 95% in a population with right-sided accessory pathways [22]. Our result of an overall 94% success in complete zero-fluoroscopy (and 100% for right-sided procedures) is well within the desired range of success and is in line with previous observations.

Although most of the data on zero-fluoroscopy are derived from single-center experiences, an Italian multi-center trial (NO-PARTY) randomized 262 patients with SVTs to the EnSite^TMNavX^™ navigation system with minimal fluoroscopy or a conventional approach. Zero-fluoroscopy was achieved in 72% of patients in the minimal fluoroscopy group, with significant overall reduction of the radiation dose and associated late risks. Moreover, a cost-effectiveness analysis was also performed with a recommendation on acceptable extra-costs in the same series [23]. Moreover, a prospective, randomized study using the MediGuide system has also confirmed significant radiation exposure reduction, without affecting success and complication rates (although this latter method requires fluoroscopy at the beginning of the study, and, therefore, is not entirely zero-fluoroscopic) [24].

Literature data on late effects of ionizing radiation and cancer incidence during electrophysiology procedures are scarce. Authors of the randomized NO-PARTY trial assessed lifetime attributable risks of cancer incidence and mortality from equivalent organ doses calculated with Monte Carlo code, according to the Biological Effects of Ionizing Radiation empirical risk models [23]. According to their results, the lifetime attributable cancer incidence ranged between 7.3 (95% confidence interval: 3.4–12.8)–11.0 (6.0–18.6) for males and 8.2 (5.0–12.8)–15.4 (9.9–25.3) for females for minimal fluoroscopy approach and 195 (111–315)–321 (198–512) and 241 (165–350)–486 (333–773) for females for the conventional approach, per 100 000 individuals (depending on age). For lifetime attributable cancer mortality risk, their results showed 3.7 (1.5–6.9)–4.8 (2.5–8.2) for males and 4.1 (2.3–6.7)–6.1 (3.9–9.2) for females for minimal fluoroscopic approach and 94 (49–158)–136 (82–215) for males and 115 (76–171)–186 (131–265) for the conventional approach, per 100 000 individuals (depending on age). Overall, minimal fluoroscopic approach resulted in 96% reduction of lifetime attributable cancer risks, although complete zero-fluoroscopy was reached in 72% of the cases (compared with 94% reported here). Similarly, they have also calculated years of life lost and years of life affected due to predicted long term. Radiation during conventional procedures would account for a total of 32 years of life lost in a sample population of 1000 woman, aged 15 years, according to their results [23].

In addition to reduction in fluoroscopy dose, our study also confirmed less ablation time required in the typical atrial flutter subgroup. The positive effect observed on minimizing radiation confirms the previous observations [21, 24‐27]; however, the one on reduced ablation time extends those further. The difference of the ablation times did not relate to different catheter technologies, as in the typical atrial flutter subgroup similar catheters were used (FlexAbility^™, Abott Inc). The only difference in the catheter was the presence or absence of the magnetic sensor, which presumably did not affect ablation parameters. However, the two different strategies we used clearly differed and not only in the use or absence of radiation, but also in the availability of EAM during the procedures. It is known that the use of 3D EAM systems might be helpful in the ablation of typical atrial flutter [26]. The reduced ablation time might more likely be related to the EAM, rather than the lack of fluoroscopy with the novel approach. However, as no impact on ablation time was reported with the earlier version of the EAM system [28], our observation might relate to the improved navigation capacity and stability of the novel 3D EAM system. Certainly, this observation and assumption needs further clinical validation.

The EnSite Precision^™ system employs a combination of both magnetic and impedance field data to allow EAM and real-time localization of multiple catheters, with the capability to map any cardiac chamber with any catheter. The use of magnetic points with Sensor Enabled^™ catheters serves to correct impedance distortion and helps to maintain the anatomic accuracy of the geometry in the map. Using a combination of both impedance and electromagnetic technologies, the system achieves a coordinate system accuracy of 2 mm. The simultaneous collection of anatomic and electrical points from multiple electrodes leads to a significantly faster point collection vs. manual mapping [29] and superiority in high point density through the creation of 3-D models [30]. According to our first experience, the system is feasible and safe to use for a zero-fluoroscopic approach of SVTs, which results in a significant reduction of radiation exposure to the patients and staff both.