Predictors of Zero X-Ray Ablation for Supraventricular Tachycardias in a Nationwide Multicenter Experience
Background: This multicenter, prospective study evaluated the determinants of zero-fluoroscopy (ZFL) ablation of supraventricular tachycardias.
Methods and Results: Four hundred thirty patients (215 male, 55.4±22.1 years) with indication to electrophysiological study or ablation of supraventricular tachycardias were enrolled. All participating physicians agreed to follow the as low as reasonably achievable policy. A procedure was defined as ZFL when no fluoroscopy was used. The total fluoroscopy time inversely correlated to the number of procedures previously performed by each operator since study start (r=−0.112; P=0.02). Two hundred eighty-nine procedures (67.2%) were ZFL; multivariable analysis identified as predictors of ZFL: procedure after the 30th for each operator, compared with procedures up to the ninth (P=0.011; hazard ratio, 3.49; 95% confidence interval [CI], 1.79–6.80); the type of arrhythmia (P=0.031; electrophysiological study and atrioventricular nodal reentry tachycardia ablation having the highest probability of ZFL; hazard ratio, 6.87; 95% CI, 2.08–22.7 and hazard ratio, 2.02; 95% CI, 1.04–3.91, respectively); the operator’s (P=0.002) and patient’s age (P=0.009). Among operators, achievement of ZFL varied from 0% to 100%; 8 (22.8%) operators achieved ZFL in <25% of their procedures; 17 (48.6%) operators achieved ZFL in >75% of their procedures. The probability of ZFL increased by 2.8% (hazard ratio, 0.98; 95% CI, 0.97–0.99) as patient’s age decreased by 1 year. Acute procedural success was obtained in all cases.
Conclusions: The use of 3-dimensional mapping system completely avoided the use of fluoroscopy in most cases, with very low fluoroscopy time in the remaining and high safety and effectiveness profiles. Achievement of ZFL was predicted by the type of arrhythmia, operator’s experience, and patient’s age.
- catheter ablation
- radiation exposure
- tachycardia, atrioventricular nodal reentry
- tachycardia, supraventricular
See Editorial by Lindsay
WHAT IS KNOWN?
There is a relationship between radiation dose from medical imaging and the attributable lifetime risk of cancer.
X-ray exposure for cardiac electrophysiological procedures should follow the policy of as low as reasonably achievable.
WHAT THE STUDY ADDS?
The use of 3-dimensional mapping system completely avoided the use of fluoroscopy in 67% of supraventricular tachycardia ablations, with very low fluoroscopic exposition in the remaining and high safety and effectiveness profiles.
The total fluoroscopy time required during the procedure showed a trend to reduction with the increase of operator’s trust in the technique.
Achievement of zero-fluoroscopy was predicted by the type of arrhythmia, operator’s experience, and patient’s age.
Catheter ablation is a well-established therapy for treatment of clinically relevant arrhythmias both in children and adults. During the last decades, the concern for the radiation injury to the patient and the professional staff increased among the medical community.1 The relationship between radiation dose from medical imaging and the attributable lifetime risk of cancer claim for the minimization of X-ray exposure in cardiac electrophysiological practice, after the policy of as low as reasonably achievable.2 The use of new technologies, such as nonfluoroscopic mapping systems (NFMS), allows the reduction of radiation exposure during catheter ablation.3
We hypothesized that the biggest hurdle against the use of NFMS as the main imaging modality could be overcome through operator’s education about techniques for fluoroscopy reduction and the agreement to follow the European Heart Rhythm Association (EHRA) procedural workflows for the reduction of radiation dose. Aim of the present multicenter, prospective study was to evaluate the determinants of zero-fluoroscopy (ZFL) ablation of supraventricular arrhythmias.
The authors declare that all supporting data are available within the article. A nationwide network of Italian electrophysiologists was invited to participate in the study. Only physicians routinely using the CARTO system (Biosense Webster, Johnson & Johnson Medical S.p.A., CA) for supraventricular tachycardia (SVT) or complex tachycardia ablation were allowed to participate in the study. Participating physicians received education about the EHRA procedural workflows for the reduction of radiation dose and were made aware by the study director about the importance of radiological exposure reduction by the use of an NFMS. All participating physicians agreed to follow the policy of as low as reasonably achievable during the study. No specific training in the electrophysiology room was provided to any operator.
Four hundred thirty consecutive patients (215 male, 55.4±22.1 years) with indication to electrophysiological study (EPS) for noncomplex SVT, such as paroxysmal supraventricular tachyarrhythmias and typical atrial flutter (AFL), were enrolled in the study from July 2014 to March 2016, by 35 physicians among 20 participating centers. Patients with a previous documented atrial fibrillation, atypical left AFL, or left ectopic atrial tachycardia (AT) were excluded from the study. Three hundred eighty-seven patients had a 12-lead ECG documentation of the clinical tachycardia, 15 were affected by asymptomatic ventricular preexcitation, and 28 patients underwent an EPS on the basis of symptoms suggesting paroxysmal supraventricular tachyarrhythmias. All antiarrhythmic drugs were discontinued at least 5 half-lives before the procedure. The study protocol was approved by the IRBs of all participating centers.
All adult patients underwent the procedure while fasting and without sedation; in pediatric patients, procedures were performed under general anesthesia or deep sedation, based on physician’s and parent’s choice. Vascular access was obtained through the right femoral vein, right internal jugular vein and, if necessary, the left atrial was accessed by patent foramen ovale, when present, or by transseptal puncture. Whenever fluoroscopy was deemed necessary for orientation and confirmation of catheter location, it was performed using standard X-ray systems already present in all the electrophysiology laboratories.
All the physicians were agreed to try to reduce the fluoroscopy dose to the minimum compatible with adequate imaging and also to adopt the workflow recommended by the EHRA practical guide for the customization of the X-ray system to regulate the amount of radiation and image quality. Single plane X-ray detectors were used in all procedures; the detector was lowered onto the patient as much as possible throughout all procedures. All operators used a frame rate setting of 7.5 frames per second.
Flowchart Description and Main Outcome Measures
All procedures were performed with the CARTO3 mapping system (Biosense Webster, Johnson & Johnson Medical S.p.A., CA) as the only or main imaging modality to cardiac chambers navigation and catheter ablation. The procedural workflow included the following steps: cannulation of the right femoral vein and insertion of an ablation catheter; impedance calibration and compensation for respiratory movements; advancement of the catheter to mark the inferior and superior vena cava; creation of right atrial geometry by fast anatomical mapping software with the aim of defining endocardial boundaries, including tagging of the His bundle region, coronary sinus ostium, and the tricuspid valve; and advancement of the other diagnostic catheters, using the previously reconstructed venous and atrial geometry (Figure 1). If necessary, a separate geometry was acquired in a similar fashion for the left atrium. The later steps of the EPS and radiofrequency catheter ablation were left open to physician’s choice.
The following parameters were recorded for each procedure: total procedure time (defined as the time interval between the insertion of the mapping and ablation catheter and its removal); fast anatomical mapping time (the time required to reconstruct the geometry of the chamber of interest); programmed electrical stimulation time (PES; the time required for the programmed atrial and ventricular stimulation); voltage/activation mapping time (time required for the reconstruction of the voltage and activation map of the chamber of interest); ablation time (cumulative time of ablation energy delivery); total fluoroscopy time (FT; the cumulative duration of fluoroscopy used during the entire procedure); FT for fast anatomical mapping; FT for the insertion of the diagnostic catheters; FT spent during the PES; FT during the transseptal puncture; FT during voltage/activation mapping; FT during ablation; number of diagnostic catheters; and type of the mapping and ablation catheter. The total FT was used in our study as a measure of operator’s attitude to use radiation during a given procedure.4 The radiation dose during each procedure was recorded using the air kinetic energy released per unit mass (kerma)-area product (KAP), also known as the dose area product.5 The effective dose (ED) was estimated using the following formula: ED (mSv)=KAP (Gy·cm2)×0.2 (mSv/Gy·cm2).6
The primary end point of this study was to demonstrate the effect of the awareness of the ZFL techniques on the reduction of radiation exposure on 35 operators among 20 participating centers. The secondary end point of the study were the evaluation of the safety and efficacy of the procedures and the identification of the determinants of ZFL achievement.
The definition of procedural success was related to the mechanism of the patient’s tachycardia. Atrioventricular nodal reentry tachycardia (AVNRT) treatment was performed aiming at slow pathway ablation. The end point for slow pathway ablation in patients with induction of sustained AVNRT before the ablation was absence of AVNRT inducibility documented for >30 minutes after last ablation pulse, both under basal condition and during intravenous isoprenaline infusion. In patients without sustained AVNRTs inducible by PES before the ablation, the end point was either slow pathway block or absence of more than a single atrial echo beat during programmed atrial stimulation.
The end point for the ablation of concealed accessory pathway (AP) was absence of SVT inducibility for >30 minutes after last ablation pulse both under basal condition and during intravenous isoprenaline infusion, in presence of ventriculoatrial block, normalization of retrograde activation with decremental conduction, or earliest activation at the His bundle and ventriculoatrial block after administration of adenosine.
The end point for ablation of AP with manifest preexcitation was the demonstration during PES of the absence of AP conduction and ventriculoatrial block induced by intravenous adenosine.
Typical AFL ablation was deemed successful when bidirectional isthmus conduction block was confirmed by coronary sinus and low lateral right atrial pacing.
Ablation of AT was considered successful if no episodes of AT could be induced for >30 minutes after last ablation pulse, both under basal condition and intravenous isoprenaline infusion.
A procedure was defined as ZFL when no fluoroscopy was used for catheters insertion, manipulation during any mapping, EPS, and ablation; fluoroscopy was allowed only during transseptal puncture. Procedures requiring the use of >90th percentile of the total FT of the study cohort were defined as high fluoroscopy procedures (HFL).
Postablation Management and Follow-Up
Transthoracic echocardiography was performed after the procedure to rule out pericardial effusion. Careful attention was payed to discover and report any other complication that might have occurred during all steps of the workflow. Patient’s follow-up consisted of outpatient clinic visits at 3 months, 6 months, and 1 year with the aim of recording arrhythmia recurrences and reporting any late procedural complication.
Continuous variables are expressed as mean±SD; 90th percentile for total FT was evaluated; the independent samples t test or Mann–Whitney U test was used to compare normally distributed and non-normally distributed continuous variables, respectively. Categorical variables are summarized as frequency and percentage and compared using Pearson χ2 exact test.
Logistic regression models were performed to identify the factors associated with performing ZFL and HFL procedures. In particular, patient’s age, weight, height, sex, number of procedures previously performed by each operator during the study, the type of arrhythmia, previous ablation, the center, and the operator were included in the model as covariates. The final model was selected by backward stepwise (LR) procedures. Analyses were performed using SPSS software (version 24, SPSS Inc, Chicago, IL). Significance level was set equal to 0.05.
Lifetime attributable risk of mortality for cancer in 50-year-old male for 100 mSv of radiological exposure was previously reported as 290 deaths per 100 000 exposed people; lifetime attributable risk for 50-year-old female was 430 deaths per 100 000 exposed people.7,8 We derived a lifetime attributable risk of 0.0355% in a 50% mixed male and female 50-year-old population.
Thirty-five physicians with experience in noncomplex SVT ablations as first operator of 11.1±4.9 years participated in the study; operator’s age was 48.3±8.4 years. Among the 430 patients, PES confirmed the diagnosis of AVNRT in 190 patients (44.2%), AFL in 92 patients (21.4%), AT in 50 patients (11.6%), right-sided AP in 31 patients (7.2%), left-sided AP in 26 patients (6.0%), and AVNRT and AFL in 3 patients (0.7%); in 38 patients (8.8%), no arrhythmia could be induced during the PES study; those procedures were classified as EPSs. Procedures lasted 93.3±41.2 minutes. Right atrial mapping required 12.1±8.7 minutes; the PES lasted 20.8±18.1 minutes. The total ablation time was 7.3±8.6 minutes.
A Thermocool SmartTouch catheter (Biosense Webster, Johnson & Johnson Medical S.p.A., CA) 3.5-mm irrigated-tip catheter was used as first choice in 220 patients (51.2%); a Navistar (Biosense Webster, Johnson & Johnson Medical S.p.A., CA) 3.5-mm nonirrigated-tip catheter was used in 192 patients (44.7%); a Navistar DS (Biosense Webster, Johnson & Johnson Medical S.p.A., CA) 8-mm nonirrigated-tip catheter was used in 18 patients (4.2%). The operator deemed necessary to change the type of ablation catheter in 6 cases: in 2 cases, a 3.5-mm nonirrigated-tip catheter was substituted by an irrigated-tip catheter because of the type of the induced arrhythmia; in 4 cases, a change in the curve of the catheter was deemed necessary in relation to the cardiac anatomy of the patient.
Seven hundred four diagnostic catheters were used during study period, with a mean of 1.6±0.7 diagnostic catheters per procedure. There was a significant trend to reduction of diagnostic catheters used over time: 1.8±0.8 catheters were used during the first 9 procedures included in the study by each operator, 1.6±0.6 during the 10th to 19th procedure, 1.6±0.6 during the 20th to 29th procedure, and 1.3±0.5 from the 30th to last procedure (P>0.001).
Acute procedural success was obtained in all cases. One procedure-related complication was recorded in the study cohort: transient second-degree atrioventricular block type 1 in a patient with AVNRT, which completely recovered 10 hours after procedure. No pericardial effusion was recorded by postprocedural echocardiography.
During the study, 10 027 seconds of fluoroscopy was used in 430 procedures (23.3±73.2 seconds per procedure); the KAP was 1.5±11.6 Gy·cm2; the ED was 0.2±0.5 mSv. Fluoroscopy exposure for each part of the procedure is shown in Table 1.
Amount of fluoroscopy varied among the various types of procedures: total FT was higher for ablation procedures, compared with EPS (25.3±76.4 versus 3.1±9.6 seconds; P=0.001); both KAP and ED were higher for ablation procedures, compared with EPS (1.6±12.1 versus 0.1±0.5 Gy·cm2; P=0.002 and 0.2±0.5 versus 0.02±0.1 mSv; P=0.002). Total FT for EPS was 3.1±9.6 seconds, 14.3±43.3 seconds for AVNRT ablation, 17.6±35.5 seconds for right-sided AP ablation, 34.3±65.3 seconds for left-sided AP ablation, 35.0±66.5 seconds for AFL ablation, and 50.7±163.5 seconds for AT ablation; complete data are summarized in Table 2. Twelve left-sided AP were mapped and ablated by transseptal approach, which required 169.1±72.1 seconds; 8 of those procedures were ZFL.
The total FT inversely correlated to the number of procedures previously performed by each operator since study start (r=−0.112; P=0.02). The total FT for the first to ninth procedure of each operator was 28.2±67.4 seconds; it tended to decrease with the increase of the number of procedures performed by each operator: it was 19.0±50.9 seconds for the 10th to 19th procedure, 8.5±29.1 seconds for the 20th to 29th procedure, and 14.1±19.7 seconds after 30th procedure (P=0.17; Figure 2). The 90% CI for the total FT significantly decreased with the increase of the number of procedures performed by each operator: the 90% CI for the total FT was 203.7±95.5 for the first to ninth procedure of each operator, 160.3±65.6 seconds for the 10th to 19th procedure, 87.2±54.7 seconds for the 20th to 29th procedure, and 52.5±10.6 seconds after 30th procedure (P=0.011). Among the group of AVNRT, the total FT was 17.1±48.5 seconds for the first to ninth procedure of each operator, 14.3±45.1 seconds for the 10th to 19th procedure, 3.4±10.6 seconds for the 20th to 29th procedure, and 10.3±13.5 seconds after 30th procedure (P=0.7); the 90% CI for the total FT was 212.4±44.9 seconds for the first to ninth procedure of each operator, 157.5±82.0 seconds for the 10th to 19th procedure, and 37.5±10.6 seconds for the 20th to 29th procedure (P=0.024). Radiation exposure for the various types of arrhythmias is shown in Figure 2.
Two hundred eighty-nine procedures (67.2%) were completed without any use of fluoroscopy; during the remaining 141 procedures (32.8%), 71.1±114.1 seconds of fluoroscopy was used. ZFL procedures were more frequently obtained in case of EPS (34 patients, 89.5%), AVNRT ablation (134 patients, 71.1%), and right-sided AP ablation (22 patients, 71.0%), compared with AFL ablation (53 patients, 57.6%), left-sided AP ablation (17 patients, 65.4%), AT ablation (26 patients, 52.0%), and procedures including ablation of 2 different arrhythmias (AVNRT+AFL in 2 patients, 66.7%; P=0.004). After a first ZFL, the following procedure by the same operator was performed without fluoroscopy in 64.3% of cases. In 109 procedures (25.3%), the X-ray was maneuvered by a radiology technician and in 321 procedures by the operator himself (74.7%). The rate of ZFL was not significantly different whenever the X-ray was maneuvered by a radiology technician (71 procedures, 65.1%) or by the physician (218 procedures, 67.9%; P=0.54). During the procedures in which ZFL was not achieved, the FT and ED were lower when the X-ray was maneuvered by a radiology technician (12.4±39.2 seconds and 0.04±0.19 mSv), compared with physician maneuvered X-ray (27.0±81.4 seconds and 0.20±0.61 mSv; P=0.014 and P<0.001, respectively).
Multivariable analysis including as covariates patient’s age, weight, height, sex, number of procedures previously performed by each operator during the study, the type of arrhythmia, previous ablation, the center, and the operator, identified the number of procedures previously performed by each operator in the study (P=0.003), the type of arrhythmia (P=0.031), the operator (P=0.002), and patient’s age (P=0.009) as associated with performing of ZFL procedures (Figure 3; Table 3). Procedures after the 30th were associated with a higher probability of ZFL, compared with procedures up to the ninth (hazard ratio [HR], 3.49; 95% confidence interval [CI], 1.79–6.80). EPS and AVNRT ablation had a higher probability of having been performed by ZFL, compared with AT (HR, 6.87; 95% CI, 2.08–22.7; and HR, 2.02; 95% CI, 1.04–3.91, respectively). Among operators, achievement of ZFL varied from 0% to 100%; 8 (22.8%) operators performed <25% of their procedures without any use of fluoroscopy and 17 (48.6%) operators performed >75% of their procedures without any use of fluoroscopy. The probability of ZFL increased by 2.8% (HR, 0.98; 95% CI, 0.97–0.99) as patient’s age decreased by 1 year.
Forty-two procedures (9.8%) required >90th percentile of total FT for the study cohort (71.7 seconds) and were classified as HFL. AFL (16 patients, 17.4%), AT (8 patients, 16.0%), and left-sided AP ablation (4 patients, 15.4%) were more frequently HFL, compared with EPS (no patients), AVNRT ablation (11 patients, 5.8%), and right-sided AP ablation (3 patients, 9.7%; P=0.009). Multivariable analysis including as covariates patient’s age, weight, height, sex, number of procedures previously performed by each operator during the study, the type of arrhythmia, previous ablation, the center, and the operator, identified the number of procedures previously performed by each operator in the study (P<0.024), the type of arrhythmia (P=0.07), the operator (P<0.001), and patient’s height (P<0.001) as associated with performing of HFL procedures. Procedures between first and ninth and those between 10th and 19th were associated with a higher probability of HFL, compared with procedures after the 30th (HR, 16.8; 95% CI, 2.4–117.8; and HR, 21.6; 95% CI, 2.9–158.9). AFL and left-sided AP ablation were associated with a higher probability HFL use, compared with AVNRT (HR, 3.56; 95% CI, 1.46–8.63; and HR, 6.76; 95% CI, 1.69–27.0, respectively); EPS was associated to a zero probability of HFL. The probability of HFL increased by 2.6% (HR, 0.97; 95% CI, 0.96–0.98) as patient’s height increased by 1 cm.
During 12-month follow-up, no procedure-related complication was reported. Four patients with AVNRT ablation and 3 patients with AFL ablation had a documented recurrence of the same type of arrhythmia; 1 patient with AFL ablation had a following episode of atrial fibrillation; 1 patient with AP ablation had recovery of AP conduction. In 1 patient treated for AVNRT ablation, ECG monitoring with loop recorder registered a phase of transient first-degree atrioventricular block.
The present study describes the largest available multicenter experience concerning nonfluoroscopic mapping and ablation. The use of 3-dimensional mapping system completely avoided the use of fluoroscopy in most cases, with very low fluoroscopic exposition in the remaining and high safety and effectiveness profiles. The total FT required during the procedure showed a trend to reduction with the increase of operator’s trust in the technique. Achievement of ZFL was predicted by the type of arrhythmia, operator’s experience, and patient’s age.
Risks of Radiological Exposure
Radiation exposure is harmful both for the patient and the operator. Data from a cohort of >16 000 cardiac patients showed that the cumulative ED predicted the risk of cancer.9 During a standard atrial fibrillation ablation procedure, the radiological ED of 15 mSv typically provided to the patient is associated with an excess of cancer risk of 1 in 750 men of 50 years old2; the risk is even higher in female (1 in 500) and in children (1 in 200).2 Data from a randomized controlled trial comparing minimally fluoroscopic approach to conventional approach showed that a conventional electrophysiological procedure at 35 years of age results in almost 1 week of life lost and in about 2 weeks of life-affected per patient, compared with 5 hours and half a day, respectively, with the minimally fluoroscopic approach.10
Occupational doses from fluoroscopy-guided interventional procedures are the highest ones registered among the medical staff using X-ray. Cardiologists are exposed to a lifetime radiation dose of 50 to 200 mSv, corresponding to a dose equivalent of 2500 to 10 000 chest X-rays, with a projected professional lifetime attributable excess cancer risk of 1 in 100.1,11 In highly exposed physicians, adjusted odds ratio for cancer and cataract are 4.5 and 9× higher, compared with nonexposed personnel; exposed personnel also had a higher risk of orthopedic illness to the back, neck, or knee. The risks for patients and personnel should be minimized by using techniques and procedures that keep exposure to a level as low as reasonably achievable.12 Several studies demonstrated the feasibility to minimize, or set to zero, radiation exposure by the use of NFMS.13–17 However, most studies reported on single experienced operator or single-center studies enrolling a small number of patients.18
Radiological Exposure Minimization or Elimination
In the present multicenter study, 430 procedures were performed by 35 operators with differing levels of experience in ZFL and catheter ablation of SVTs. The experience confirms that NZF procedures can be performed with a safety and efficacy procedural profile at least not inferior to conventional procedures.
The use of NFM systems did not automatically lead to elimination of radiation exposure in all procedures; however, ED in the study cohort was lower than typically reported in literature for all types of procedures. We reported the use of 0.2±0.5 mSv ED for ablation procedures, which seems lower than typical radiation doses (15.2 mSv; range, 1.6–59.6 mSv) reported in literature.2 The reduction in radiation exposure with ZFL technique, although negligible for the single patient undergoing a single procedure in his life, might be of interest for the whole exposed population. If we consider that at least 296 798 patients undergo catheter ablation every year in ESC member countries,19 we can estimate that the exposure of 50-year-old patients to 15 mSv (typical of catheter ablation procedure without ZFL technique) would be associated with ≈158 deaths every year, in addition to >59 000 of them expected to die for cancer. Application of ZFL, by reducing the radiation exposure by several times, might help to protect our patients: only few drops in an ocean, but still some lives not dying for cancer.
Radiation exposure was very low since the first study procedures and usually inferior to values typically reported in literature. Although there was no significant variation of procedure time over study period, thus confirming a steady-state level of operator’s experience in SVT ablation, radiation exposure showed a progressive trend to reduction overtime. The presence of the learning curve effect is also confirmed by the progressive reduction of diagnostic catheters used during study period. These results confirm that awareness and operator’s commitment to reduce radiation exposure are important determinants of its achievement.
Although there was no commitment to perform ZFL procedures by study protocol, but only to reduce radiation exposure as low as possible, 67.2% of procedures were completed without any use of fluoroscopy, and 48.6% of operators performed >75% of their procedures without any use of fluoroscopy. ZFL mapping and ablation was performed in the majority of procedures, in all types of arrhythmias, thus suggesting that operators consider nonfluoroscopic navigation as an adequate imaging for most cases. The ZFL mapping was frequently achieved in procedures requiring catheter navigation in areas with a reproducible chamber geometry, such as EPS, AVNRT, and right-sided AP ablation. In case of AVNRT ablation, the NFMS provides a precise definition of the triangle of Koch; the conduction system can be tracked, and its footprint can be shown on the map, not only as a single point, but usually as an area; during mapping and ablation, the distance between the catheter and the His bundle can be continuously evaluated; points of previous ineffective ablation are recorded and shown on the map, thus allowing a precise selection of the site of further radiofrequency applications. During AP mapping, the lateral versus septal orientation of the catheter and its relationship with the valvular annuls can be easily monitored. About 30% of cases of left AP ablation were performed by transseptal approach, which required 169.1±72.1 seconds of fluoroscopy in our series; in patient with contraindications to X-ray exposure, intracardiac echocardiography can be a successful technique to guide the transseptal puncture. The following left atrial and mitral annulus mapping can be facilitated by adequate transseptal sheath positioning; to reduce fluoroscopy use during sheath manipulation, sheath visualization by NFMS would be the further step in ZFL technique evolution. The support of an NFMS during cavotricuspid isthmus ablation allows the simultaneous visualization of the catheter on right and left anterior oblique view without fluoroscopy; this helps the operator in delivering radiofrequency pulses along a continuous line without gaps, favoring the complanarity of the lesions. Previous studies demonstrate that ZFL ablation significantly reduced years of life lost and years of life affected by cancer, thus reducing the costs for the health system by €1151 to €1918.10 The extra cost of the NFMS thus seems affordable in many countries.
Although the reduction in fluoroscopy was progressive and sometimes reported also for the first operator’s procedure, ZFL was more frequently achieved after the 30th procedure of each operator during study period. This might suggest that systematical implementation of ZFL may require an adequate training; operators who need to perform procedure requiring very low or ZFL exposure, such as pediatric patients, should have previously performed a significant amount of procedures strictly following the as low as reasonably achievable principle.
Data about radiological exposure of individual operators were not systematically collected; it is possible that an active reporting of these data to the operators might represent an important step in the awareness of radiological exposure, and it might further reduce the operator wish to use fluoroscopy. Given the multicenter, nonrandomized type of the study, comparison between ZFL and conventional procedure can only be inferred from literature; further randomized controlled studies can evaluate the real radiation saving by ZFL. Because all procedures were performed with the CARTO mapping system for noncomplex arrhythmias, present findings should not be directly applied to mapping with other mapping systems, mapping in patients with anomalies in the anatomy of cardiac chambers, or ablation of complex arrhythmias. In the present study, operators could perform procedures following the order of clinical practice presentation; we cannot exclude that a more rigid study protocol (no other SVT ablations before ZFL in AVNRT) may allow a shorter learning curve.
The most important variables like KAP and ED depend on several variables, including the use of cine acquisitions, the type and configuration of the X-ray system used, operator training (collimation, less-irradiating angulations), and patients characteristics.
Very low radiological exposure is required for SVT ablation when an NFMS is used; use of fluoroscopy can be completely avoided in most cases, without any reduction of the safety and effectiveness profile. Operator’s awareness and will are key determinants of the reduction in fluoroscopic use. ZFL procedures can be obtained in most cases after a relatively short learning curve.
List of other ZeroFluoro Study Group participants: Sandra Badolati, MD; Claudia Baiocchi, MD; Sebastiano Belletti, MD; Andrea Di Cori, MD; Marco Galeazzi, MD; Edoardo Gandolfi, MD; Matteo Iori, MD; Francesco Isola, MD; Riccardo Massa, MD; Giovanni Motta, MD; Massimo Pala, MD; Elena Piazzi, MD; Fabio Quartieri, MD; Luca Segreti, MD; Antonello Vado, MD; Gabriele Vignati, MD
Dr Della Bella is consultant for St. Jude Medical and has received honoraria for lectures from Biosense Webster, St. Jude Medical and Biotronik. V. Napoli is an employee of Johnson & Johnson Med, Biosense Webster Italy. Dr Vergara is consultant for Biosense Webster. The other authors report no conflicts.
* A list of all ZeroFluoro Study Group participantcs is given in the Appendix.
Circ Arrhythm Electrophysiol is available at http://circep.ahajournals.org.
- Received July 2, 2017.
- Accepted January 16, 2018.
- © 2018 American Heart Association, Inc.
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