Abstract
Catheter ablation of atrial fibrillation (AF) focuses on pulmonary vein (PV) ablation with or without additional atrial substrate modification. These procedures require significant fluoroscopy exposure. A new 3D non-fluoroscopic navigation system (CARTO® 3 System, Biosense Webster, CA, USA) that allows precise location visualization of diagnostic and ablation catheters was evaluated for its impact on fluoroscopic exposure during AF ablation procedures.
Two groups of patients were treated by our centres for drug refractory AF. One group was treated using the new CARTO® 3 system to guide catheter ablation (Group A, 117 patients). The other group was treated using the CARTO® XP system (Biosense Webster) 3 months previously (Group B, 123 patients). For both groups, circumferential PV ostia ablation was performed; PV isolation was validated using a circular catheter placed at each ostium. There was no difference in any clinical characteristics (age, sex, AF type, left atrium diameter and volume, and heart disease) among the two study groups. The mean number of PVs identified and isolated per patient was similar in both groups, as were the mean procedural duration and radiofrequency time. However, mean fluoroscopic time was significantly reduced in Group A (15.9±12.3 min) as compared with Group B (26±15.1 min) (P< 0.001).
This multicentre observational study demonstrates a significant reduction of fluoroscopy exposure using a new 3D non-fluoroscopic mapping system to guide AF catheter ablation.
Introduction
Since the discovery of the pivotal role of the pulmonary veins (PVs) in initiating and perpetuating atrial fibrillation (AF),1 several strategies for performing AF radiofrequency (RF) catheter ablation have been proposed,2,3 with PV isolation remaining the cornerstone of AF ablation.4,5 A major limitation of AF ablation is the procedure length with significant exposure to fluoroscopy. Several technological innovations, to facilitate AF ablation procedures, have been proposed.6–11 The aim of this retrospective, controlled, multicentre study was to investigate whether circumferential PV isolation guided by a novel non-fluoroscopic imaging system, which allows visualization of both diagnostic and ablation catheters, reduces the procedure and fluoroscopic exposure times of RF catheter ablation.
Methods
Study population
The study population consisted of 240 consecutive patients (mean age 59 ± 10 years, 70% male, 63% paroxysmal AF, mean left atrium diameter 44.5±6.1 mm, 59% with structural heart disease) suffering from symptomatic documented paroxysmal or persistent AF refractory to more than one antiarrhythmic drugs. All patients underwent a first catheter ablation in six Italian institutions.
Study protocol
This is a retrospective controlled study to evaluate the impact on procedure parameters of a novel technology (CARTO® 3, Biosense Webster, Inc., Diamond Bar, CA, USA) used to guide PV ablation in patients with symptomatic drug-refractory AF. Group A (117 consecutive patients, mean age 60 ± 11 years, 68% male, 63% paroxysmal AF) underwent the procedure using the novel technology, while Group B (123 consecutive patients, 58 ± 10 years, 72% male, 63% paroxysmal AF) underwent the procedure using an older technology (CARTO® XP System, Biosense Webster, Inc.). This was the first PV ablation procedure performed on all patients. Group A patients underwent AF ablation in the first 3 months of use of CARTO® 3 system in each centre, whereas Group B patients underwent the same procedure supported by CARTO® XP system, in a similar time interval, just before introduction of the CARTO® 3 system.
In each centre, the same operators worked with both navigation systems; the operators all had comparable procedural experience with both systems. All centres had a similar experience (>5 years) using navigation systems to assist AF ablation. Procedures parameters (skin-to-skin procedural duration, overall fluoroscopy time, overall RF energy time, and acute procedure outcome) and operator names were routinely recorded in the laboratory log. This study was approved by the institutional review committees of all centres, and all patients signed informed consents.
Electrophysiologic procedure and use of the navigation systems
In each centre, pre-procedure and post-procedure patient management, as well as intra-procedure anticoagulation policy, were in accordance with the consensus documents.4,5 After placing the catheters and achieving transseptal catheterization, a 7.5 F open-irrigation ablation catheter (Navistar® Thermocool, Biosense Webster, Inc.) and a 7 F deca- or duodecapolar circular mapping catheter (Lasso®, Biosense Webster, Inc.) were placed in the left atrium. Left atrium electroanatomical reconstruction has been already described.10 For both groups, when available, a segmented 3D rendering of a computed tomography (CT) or magnetic resonance (MR) scan of the left atrium and PVs was imported to the navigation systems using the CARTOMERGE® module (Biosense Webster Inc.. After registration of the imported image, accuracy of superimposition with the electroanatomic map was verified and the mapping/ablation catheter was navigated in the left atrium and around the PVs os with minimal use of fluoroscopy. The integration between 3D MR/CT image and anatomical reconstruction was considered accurate enough to guide RF ablation when overall integration error was <3 mm and catheter navigation inside the chamber was successfully obtained by the guidance of registered image.
CARTO® 3 system features
Ablation procedures facilitated by the CARTO® XP system have been reported in detail elsewhere.3,10 With the introduction of the CARTO® 3 system, the ability to visualize manipulation and placement of circular mapping catheters in each vein may further reduce fluoroscopy time. This new system also enables catheter stability during ablation and identification of each catheter electrode-pair position. Visualization of catheters and electrode pairs is provided via real-time on-screen display of a geometrically reliable icon representing the distal part of the LASSO® catheter along with electrode positions (Figure 1).
Fluoroscopic image (A) and CARTO® 3 system reconstruction (B) view showing mapping and ablation catheters. Fluoroscopic projection was 30° right anterior oblique.
Based on the magnetic location technology of the CARTO® XP system, the CARTO® 3 system allows fast anatomical mapping of the cardiac chambers. Fast anatomical mapping provides a volumetric reconstruction performed via a sensor-based catheter (Navistar® and LassoNAV®). In this study, only Navistar® catheter was used for fast anatomical mapping. During fast anatomical mapping, the system sets the mapping catheter motion to stable by averaging catheter locations over a one-second period. Based on the location sensor findings and the known mechanical properties of the sensor-based catheter, volume data are recorded continuously as the catheter is navigated inside the chamber. Using volume data acquired from the outer surface, the system generates an interpolated surface reconstruction of the chamber. The CARTO® 3 system combines the magnetic technology of the CARTO® XP system with the new advanced catheter location technology to provide accurate visualization of all catheters connected to the system. The advanced catheter location technology is a hybrid technology, which combines magnetic data with additional current-based data. Each electrode in every catheter connected to the system emits a low-power current with a unique frequency. These currents are measured by six surface passive patches (three on the back and three on the chest). An algorithm matches current measurement from the patches with magnetic locations obtained by the sensor-based catheter, providing electrode location. Optimal shaft visualization of each catheter is achieved based on the characteristics of each catheter.
Catheter ablation
For both groups, procedure end-point was PV disconnection with demonstration of persistent bidirectional conduction block. Radiofrequency energy was delivered using maximum power up to 42 W, temperature cut-off at 43 °C, and irrigation rate up to 30 mL/min, to produce a circumferential lesion around the proximal part of the PV ostia. The PV ostia were identified based on the local electrical signal and the morphology in the CT or MR images. Depending on the operators’ preferences at each centre, lesions were created by positioning the catheter and sequential point-by-point application of RF energy, or by applying RF energy as the catheter was dragged along the PV ostium.
Upon completion of the circumferential ablation, a circular catheter was placed at the PV ostium for PV potential mapping. For Group A, the CARTO® 3 system advanced catheter location feature was used to visualize the circular mapping catheter; the loop and all the electrodes were visualized inside the left atrium or PV map. Pulmonary vein potentials persisting on specific dipoles of the circular catheter were highlighted on 3D visualization of circular catheter (Figure 2). If PV potentials remained and were connected to the left atrium, segmental ostial ablation targeting electrical breakthroughs was performed under guidance of circular mapping, with the goal of PV isolation. Pulmonary vein isolation was considered successful when PV potentials disappeared or were disconnected (entry block), and when pacing with a 2 ms stimulus at twice the amplitude of the stimulation threshold, from all five bipolar electrodes of the circular mapping catheter, allowed local capture without left atrium capture (exit block).
(A) Endocardial recordings showing the left superior pulmonary vein activity before ablation. Bipole 20A 13-14 shows the earliest activation. I: surface electrocardiogram lead recording; 20A 1-20: bipolar endocardial recordings from circumferential mapping catheter; CARTO® 3 system 1-2: bipolar endocardial recordings from distal bipole on the coronary sinus catheter; Map 1-2: bipolar endocardial recordings from distal bipole on the ablation catheter. (B) CARTO® 3 system views showing a duodecapolar circular mapping catheter placed at the ostium of left superior pulmonary vein and an ablation catheter close to a specific dipole (yellow circles) of the mapping catheter, corresponding to 20A 13-14 bipole.
Statistical analysis
Descriptive statistics are presented as mean ± standard deviation for continuous variables and numbers with percentages for categorical variables. Differences between continuous variable were assessed by Student's t-test or Mann–Whitney U test, depending on the normality of data. Comparison between categorical data was assessed by χ2 test (Pearson, Yates, or Fisher's exact test as appropriate). In all analysis, P < 0.05 was considered statistically significant.
Results
Clinical and anatomical characteristics
There were no differences in any clinical characteristics (Table 1) between the two study groups. A CARTOMERGE® procedure was performed in 85% of Group A patients and 89% of Group B patients (P = 0.35), guided by MR (54% of Group A patients and 64% of Group B patients, P = 0.1) or CT (36% of Group A patients and 26% of Group B patients, P = 0.1) imaging. A mean of 4.1 ± 0.2 PVs/patient were identified in Group A and a mean of 4.1 ± 0.3 PVs/patient were identified in Group B (P = 0.16). Anatomical variations were balanced between the groups: a common ostium was found in 24% of Group A patients and in 17% of Group B patients (P = 0.19), whereas five PVs were identified in 7% of Group A patients and 13% of Group B patients (P = 0.11). A comparable number of PVs/patient were isolated in the two groups (3.9 ± 0.6 in Group A vs. 4 ± 0.5 in Group B; P = 0.14).
Clinical characteristics of both study groups
| Group A (CARTO® 3 system) | Group B (CARTO® XP system) | P | |
|---|---|---|---|
| Mean age (years) | 60 ± 11 | 58 ± 10 | 0.13 |
| Sex (female) | 32% | 28% | 0.59 |
| Mean left atrium diameter (mm) | 44.4 ± 6.4 | 44.7 ± 5.9 | 0.80 |
| Mean left atrium volume (mL) | 107.1 ± 61 | 114.7 ± 46.2 | 0.60 |
| Mean left ventricle ejection fraction (%) | 60.4 ± 6.9 | 59 ± 6.5 | 0.14 |
| Paroxysmal atrial fibrillation | 63% | 63% | 0.74 |
| Previous non-atrial fibrillation ablation | 15% | 8% | 0.08 |
| Previous stroke | 3% | 2% | 0.65 |
| Structural heart disease | 61% | 58% | 0.64 |
| Hypertension | 52% | 46% | 0.37 |
| Ischaemic | 6% | 2% | 0,17 |
| Dilated cardiomyopathy | 5% | 2% | 0.27 |
| Valvulopathy | 3% | 5% | 0.34 |
| Group A (CARTO® 3 system) | Group B (CARTO® XP system) | P | |
|---|---|---|---|
| Mean age (years) | 60 ± 11 | 58 ± 10 | 0.13 |
| Sex (female) | 32% | 28% | 0.59 |
| Mean left atrium diameter (mm) | 44.4 ± 6.4 | 44.7 ± 5.9 | 0.80 |
| Mean left atrium volume (mL) | 107.1 ± 61 | 114.7 ± 46.2 | 0.60 |
| Mean left ventricle ejection fraction (%) | 60.4 ± 6.9 | 59 ± 6.5 | 0.14 |
| Paroxysmal atrial fibrillation | 63% | 63% | 0.74 |
| Previous non-atrial fibrillation ablation | 15% | 8% | 0.08 |
| Previous stroke | 3% | 2% | 0.65 |
| Structural heart disease | 61% | 58% | 0.64 |
| Hypertension | 52% | 46% | 0.37 |
| Ischaemic | 6% | 2% | 0,17 |
| Dilated cardiomyopathy | 5% | 2% | 0.27 |
| Valvulopathy | 3% | 5% | 0.34 |
Clinical characteristics of both study groups
| Group A (CARTO® 3 system) | Group B (CARTO® XP system) | P | |
|---|---|---|---|
| Mean age (years) | 60 ± 11 | 58 ± 10 | 0.13 |
| Sex (female) | 32% | 28% | 0.59 |
| Mean left atrium diameter (mm) | 44.4 ± 6.4 | 44.7 ± 5.9 | 0.80 |
| Mean left atrium volume (mL) | 107.1 ± 61 | 114.7 ± 46.2 | 0.60 |
| Mean left ventricle ejection fraction (%) | 60.4 ± 6.9 | 59 ± 6.5 | 0.14 |
| Paroxysmal atrial fibrillation | 63% | 63% | 0.74 |
| Previous non-atrial fibrillation ablation | 15% | 8% | 0.08 |
| Previous stroke | 3% | 2% | 0.65 |
| Structural heart disease | 61% | 58% | 0.64 |
| Hypertension | 52% | 46% | 0.37 |
| Ischaemic | 6% | 2% | 0,17 |
| Dilated cardiomyopathy | 5% | 2% | 0.27 |
| Valvulopathy | 3% | 5% | 0.34 |
| Group A (CARTO® 3 system) | Group B (CARTO® XP system) | P | |
|---|---|---|---|
| Mean age (years) | 60 ± 11 | 58 ± 10 | 0.13 |
| Sex (female) | 32% | 28% | 0.59 |
| Mean left atrium diameter (mm) | 44.4 ± 6.4 | 44.7 ± 5.9 | 0.80 |
| Mean left atrium volume (mL) | 107.1 ± 61 | 114.7 ± 46.2 | 0.60 |
| Mean left ventricle ejection fraction (%) | 60.4 ± 6.9 | 59 ± 6.5 | 0.14 |
| Paroxysmal atrial fibrillation | 63% | 63% | 0.74 |
| Previous non-atrial fibrillation ablation | 15% | 8% | 0.08 |
| Previous stroke | 3% | 2% | 0.65 |
| Structural heart disease | 61% | 58% | 0.64 |
| Hypertension | 52% | 46% | 0.37 |
| Ischaemic | 6% | 2% | 0,17 |
| Dilated cardiomyopathy | 5% | 2% | 0.27 |
| Valvulopathy | 3% | 5% | 0.34 |
Procedure parameters
Mean fluoroscopy time exposure (15.9 ± 12.3 min for Group A vs. 26 ± 15.1 min for Group B, P < 0.001) was significantly shorter in Group A. However, there was no difference in the mean procedural duration (157 ± 67 min for Group A vs. 159 ± 65 min for Group B, P = 0.8) and mean RF duration (41 ± 15 min for Group A vs. 42 ± 15 min for Group B, P = 0.63). The overall reduction in fluoroscopy time in Group A as compared with Group B was –39% with a wide range between each centre (from −25 to −75%) (Table 2). The CARTO® 3 system allowed for significantly reduced fluoroscopy time in both paroxysmal AF patients (from 26.3 ± 15.2 to 14.2 ± 12.7 min, P < 0.001) and persistent AF patients (from 25.3 ± 15.1 to 18.8 ± 11.1 min, P = 0.02) with a trend towards a greater reduction in patients with paroxysmal AF (−46 vs. −26%)
Mean fluoroscopy time in each centre
| Centre (patients enrolled) | Group A (CARTO® 3 system) (min) | Group B (CARTO® XP system) (min) | P | Δ (%) |
|---|---|---|---|---|
| 1 (36) | 15.06 ± 5 | 34 ± 7.68 | <0.001 | −56 |
| 2 (60) | 2.48 ± 1.17 | 10.12 ± 3.74 | <0.001 | −75 |
| 3 (30) | 12.47 ± 8.76 | 20.51 ± 10.69 | 0.03 | −39 |
| 4 (31) | 27.13 ± 10.11 | 39.88 ± 9.11 | <0.001 | −32 |
| 5 (33) | 30.98 ± 10.48 | 41.06 ± 13.96 | 0.03 | −25 |
| 6 (50) | 17.08 ± 9.54 | 24.56 ± 12.44 | 0.02 | −30 |
| Overall | 15.9 ± 12.3 | 26 ± 15.1 | <0.001 | −39 |
| Centre (patients enrolled) | Group A (CARTO® 3 system) (min) | Group B (CARTO® XP system) (min) | P | Δ (%) |
|---|---|---|---|---|
| 1 (36) | 15.06 ± 5 | 34 ± 7.68 | <0.001 | −56 |
| 2 (60) | 2.48 ± 1.17 | 10.12 ± 3.74 | <0.001 | −75 |
| 3 (30) | 12.47 ± 8.76 | 20.51 ± 10.69 | 0.03 | −39 |
| 4 (31) | 27.13 ± 10.11 | 39.88 ± 9.11 | <0.001 | −32 |
| 5 (33) | 30.98 ± 10.48 | 41.06 ± 13.96 | 0.03 | −25 |
| 6 (50) | 17.08 ± 9.54 | 24.56 ± 12.44 | 0.02 | −30 |
| Overall | 15.9 ± 12.3 | 26 ± 15.1 | <0.001 | −39 |
Mean fluoroscopy time in each centre
| Centre (patients enrolled) | Group A (CARTO® 3 system) (min) | Group B (CARTO® XP system) (min) | P | Δ (%) |
|---|---|---|---|---|
| 1 (36) | 15.06 ± 5 | 34 ± 7.68 | <0.001 | −56 |
| 2 (60) | 2.48 ± 1.17 | 10.12 ± 3.74 | <0.001 | −75 |
| 3 (30) | 12.47 ± 8.76 | 20.51 ± 10.69 | 0.03 | −39 |
| 4 (31) | 27.13 ± 10.11 | 39.88 ± 9.11 | <0.001 | −32 |
| 5 (33) | 30.98 ± 10.48 | 41.06 ± 13.96 | 0.03 | −25 |
| 6 (50) | 17.08 ± 9.54 | 24.56 ± 12.44 | 0.02 | −30 |
| Overall | 15.9 ± 12.3 | 26 ± 15.1 | <0.001 | −39 |
| Centre (patients enrolled) | Group A (CARTO® 3 system) (min) | Group B (CARTO® XP system) (min) | P | Δ (%) |
|---|---|---|---|---|
| 1 (36) | 15.06 ± 5 | 34 ± 7.68 | <0.001 | −56 |
| 2 (60) | 2.48 ± 1.17 | 10.12 ± 3.74 | <0.001 | −75 |
| 3 (30) | 12.47 ± 8.76 | 20.51 ± 10.69 | 0.03 | −39 |
| 4 (31) | 27.13 ± 10.11 | 39.88 ± 9.11 | <0.001 | −32 |
| 5 (33) | 30.98 ± 10.48 | 41.06 ± 13.96 | 0.03 | −25 |
| 6 (50) | 17.08 ± 9.54 | 24.56 ± 12.44 | 0.02 | −30 |
| Overall | 15.9 ± 12.3 | 26 ± 15.1 | <0.001 | −39 |
No complications were observed in any of the patients.
Discussion
In patients with paroxysmal or persistent AF, refractory to antiarrhythmic drugs, circumferential PV isolation guided by a new 3D non-fluoroscopic mapping system (CARTO® 3 system), significantly reduced fluoroscopic exposure when compared with circumferential PV isolation guided by 3D mapping (CARTO® XP system). The result was not related to operator expertise, even when a centre's learning curve for CARTO® 3 was included.
Radiation exposure
A potential but less easily recognized complication associated with AF catheter ablation results from the delayed effects of radiation on patients, resulting from prolonged fluoroscopy times. These risks include acute and subacute skin injury,12,13 as well as radiation-induced cancer and genetic abnormalities.14–19 This is of particular concern because of the complex nature of this procedure, typically involving double-transseptal catheterization, PV angiography, and extensive RF application. Moreover, patients undergoing a catheter ablation of AF often receive a CT scan prior to the procedure. In addition, AF ablation procedures are often performed on obese patients, increasing fluoroscopic exposure to patients and operators.20 Lickfett et al.21 reported mean fluoroscopy durations for AF procedures of >60 min in both left anterior oblique and right anterior oblique projections. The mean peak skin doses were 1.0 ± 0.5 Gy in right anterior oblique and 1.5 ± 0.4 Gy in left anterior oblique projection. This translates into a lifetime risk of excess fatal malignancies (normalized to 60 min of fluoroscopy) of 0.07% for female and 0.1% for male patients. The relatively low radiation exposure to the patients in this study, despite the prolonged fluoroscopy durations, was attributable to the state-of-the-art very low frame-rate pulsed fluoroscopy, the avoidance of magnification, and the optimal adjustments of fluoroscopy exposure-rates. The resulting lifetime risk of malignancy was thus within the range previously reported for ablation of standard types of supraventricular arrhythmias.17–19 However, Lickfett et al.21 demonstrated that catheter ablation of AF required significantly greater fluoroscopy duration and radiation exposure (more than four-fold) than simpler catheter ablation procedures. Similar data have been reported also by Macle et al.,22 although, using a less sensitive method to assess the peak skin doses, a lower patient radiation exposure (dose) was observed. Although single-procedure exposure appears to represent a very low cancer risk, repeated procedures, often need in AF ablation, may indeed begin to produce a measurable increased risk, and every effort should be made to minimize total exposure. Electroanatomic and remote navigation systems that facilitate catheter placement and stability may help to reduce radiation exposure.
Comparison with previous studies
In an unselected population referred for supraventricular and ventricular arrhythmias catheter ablation, Sporton et al.23 compared the routine use of electroanatomic imaging (CARTO® XP system) with that of conventional fluoroscopically guided activation mapping. Acute procedural success was similar with either strategy, as was procedure duration (144 ± 58 vs. 125 ± 48 min, P = 0.07). The CARTO® XP system was associated with a substantial reduction in fluoroscopy time (9.3 ± 7.6 vs. 28.8 ± 19.5 min, P < 0.001) and radiation dose (6.2 ± 6.1 vs. 20.8 ± 32.7 Gy, P = 0.003). Another technology, Ensite NavX® (St Jude Medical, St Paul, MN, USA), combines the ability to locate all catheters non-fluoroscopically and, if necessary, construct a 3D geometry. Earley et al.24 compared the utility of non-fluoroscopic mapping systems (CARTO® XP system and Ensite NavX®) with that of conventional mapping in patients referred for catheter ablation of a wide variety of arrhythmias (excluding AF, atypical atrial flutter, ventricular tachycardia in structural heart disease, and complete atrioventricular nodal ablation). They found that Ensite NavX® and CARTO® XP procedures had similar effectiveness and safety to a conventional approach; however, they both reduced X-ray exposure, with NavX® producing a significantly greater effect than CARTO® XP. Recently, Hindricks et al.25 compared the results of catheter ablation to cure typical atrial flutter using conventional ablation strategy and electroanatomically guided mapping and ablation (CARTO® XP system). They found that cavotricuspid isthmus ablation to cure typical atrial flutter was highly effective and safe, both in the conventional and the electroanatomically guided ablation group. The use of electroanatomical mapping system significantly reduced the fluoroscopy exposure time by almost 50%, however, at the expense of increased cost of the procedure.
Less data are available for AF patients. Rotter et al.7 performed a randomized study on 72 patients undergoing catheter ablation for symptomatic drug refractory AF using a non-fluoroscopic navigation system (NavX®). Their prospectively randomized study demonstrated significant reduction of fluoroscopy exposure and procedural duration using a supplementary non-fluoroscopic imaging system for AF ablation. Initial reduction in fluoroscopy time observed with CT image integration into the CARTO® XP system26 has not been confirmed by a randomized study27 and a multicentre registry.10 Our study demonstrates a significant reduction in fluoroscopy time, without any effect on the overall procedure duration, in patients who underwent AF catheter ablation guided by the CARTO® 3 system. This new electroanatomical mapping system allows real-time visualization of ablation and diagnostic catheters, like the NavX® system evaluated by Rotter et al.7 Both non-fluoroscopic navigation systems allow real-time assessment of wall contact and catheter stability as well as assessment of the anatomical position and the relationship between the ablation catheter and the circular mapping catheter. It seems reasonable to suppose that the visualization of diagnostic catheters plays a pivotal role in reducing fluoroscopy time during AF catheter ablation procedures for PV isolation. Recently a single-centre study28 that randomly assigned 120 patients with symptomatic AF to fluoroscopy alone, electroanatomical integration (CARTOMERGE®), and electroanatomical integration plus catheters visualization (CARTO® 3 System) guided procedures confirmed that image integration and, to a larger extent, visualization of multiple catheters allowed a minimal use of fluoroscopy in transcatheter AF ablation. However, operator expertise may play a crucial role in fluoroscopy time, procedural time, and clinical success.4,5 Although a wide range in mean fluoroscopy time was observed between different operators in our study, the decrease in overall fluoroscopy time was observed by all centres. This confirms that the reduced fluoroscopy time using the CARTO® 3 system is not operator dependent and is observed even when a centre's ‘learning curve’ for the CARTO® 3 system is included.
Study limitations
One limitation of this study is that data were gathered as soon as the CARTO® 3 system became available at each centre. Since the CARTO® 3 system did not contribute to reducing overall procedure time, it should be noted that most centres involved in this study were using this new technology for the first time and that greater experience may lead to a further reduction in procedure duration and fluoroscopy time. Another important limitation is that this was not a randomized study. We cannot, therefore, exclude an enrolment bias, although no difference was observed in any clinical characteristics between the two study groups. However, observational studies like this can provide additional information, since they are fully representative of everyday clinical practice, in which several factors underestimated in prospective trials, such as the different experience of the involved centres, may play a role. For this reason, observational studies will be of particular importance in monitoring and guiding the incorporation of this therapeutic procedure into clinical practice. Finally, since our study was designed to investigate whether a novel non-fluoroscopic imaging system reduces the procedure and fluoroscopic exposure times of RF catheter ablation, we did not collect data on long-term outcomes (success rate and complications).
Conclusions
The evaluated non-fluoroscopic imaging system is safe and allows significant reduction of fluoroscopy exposure and duration during AF catheter ablation. However, further randomized studies are needed to compare this system with other well-established non-fluoroscopic imaging systems.
Conflict of interest: R.D.P. and E.B. are consultants for Biosense Webster.
Acknowledgements
The authors thank Lidia Visigalli, BS, and Serena Dottori, BS, from Biosense Webster, Italy, for their technical support.
