Fluoroscopy usage in contemporary interventional electrophysiology: Insights from a European registry

Abstract Background Fluoroscopy has been an essential part of every electrophysiological procedure since its inception. However, till now no clear standards regarding acceptable x‐ray exposure nor recommendation how to achieve them have been proposed. Hypothesis Current norms and quality markers required for optimal clinical routine can be identified. Methods Centers participating in this Europe‐wide multicenter, prospective registry were requested to provide characteristics of the center, operators, technical equipment as well as procedural settings of consecutive cases. Results Twenty‐five centers (72% university clinics, with a mean volume of 526 ± 348 procedures yearly) from 14 European countries provided data on 1788 cases [9% diagnostic procedures (DP), 38% atrial fibrillation (AF) ablations, 44% other supraventricular (SVT) ablations, and 9% ventricular ablations (VT)] conducted by 95 operators (89% male, 41 ± 7 years old). Mean dose area product (DAP) and time was 304 ± 608 cGy*cm2, 3.6 ± 4.8 minutes, 1937 ± 608 cGy*cm2, 15.3 ± 15.5 minutes, 805 ± 1442 cGy*cm2, 10.6 ± 10.7 minutes, and 1277 ± 1931 cGy*cm2, 10.4 ± 12.3 minutes for DP, AF, SVT, and VT ablations, respectively. Seven percent of all procedures were conducted without any use of fluoroscopy. Procedures in the lower quartile of DAP were performed more frequently by female operators (OR 1.707, 95%CI 1.257‐2.318, P = .001), in higher‐volume center (OR 1.001 per one additional procedure, 95%CI 1.000‐1.001, P = .002), with the use of 3D‐mapping system (OR 2.622, 95%CI 2.053‐3.347, P < .001) and monoplane x‐ray system (OR 2.945, 95%CI 2.149‐4.037, P < .001). Conclusion Exposure to ionizing radiation varies widely in daily practice for all procedure. Significant opportunities for harmonization of exposure toward the lower range has been identified.

and 1277 ± 1931 cGy*cm 2 , 10.4 ± 12.3 minutes for DP, AF, SVT, and VT ablations, respectively. Seven percent of all procedures were conducted without any use of fluoroscopy.
Conclusion: Exposure to ionizing radiation varies widely in daily practice for all procedure. Significant opportunities for harmonization of exposure toward the lower range has been identified. of patients and personnel to ionizing radiation. Exposure to ionizing radiation may be harmful both for personnel and for patients, with inherent risk of neoplasms due to long-term exposure representing the biggest concern. 1 Electrophysiology procedures were initially performed solely with the use of fluoroscopy but the development of novel mapping systems has led to a dramatic decrease or even a complete abandonment of fluoroscopy during the last decade. 2 The U.S. Nuclear Regulatory Commission recommends making every effort to keep exposure to ionizing radiation as low as reasonably achievable (ALARA), a statement that is accepted and endorsed by all the major societies of physicians working with ionizing radiation. [1][2][3] The purpose of "Go for Zero Fluoroscopy" project is to assess current routine and practice with the use of fluoroscopy in electrophysiology centers and to identify factors associated with low radiation dose during procedures.

| Primary objective
The study aimed to describe the real-life, contemporary use of fluoroscopy in interventional electrophysiology across European countries. The main goal of this analysis was to identify factors associated with the low dose of radiation defined as procedures within the lower quartile of DAP.

| Study design and setting
The Go for Zero Fluoroscopy project is a prospective, international, observational registry of consecutive patients undergoing any type of interventional electrophysiological procedure. Design, oversight, and logistics was conducted under the "Go for Zero Fluoroscopy Project" of the European Hearth Rhythm Association's Young EP committee (EHRA YEP). The study was conducted in 25 centers from 14 European countries (full list provided in the Appendix 1). Local principal investigators obtained approval by the local Institutional Review Board, depending on regulations in each country.

| Study participants
Centers were asked to provide anonymized data regarding the procedural setting of maximum 20 consecutive electrophysiological interventions conducted by maximum five different operators. This limit was introduced in order to prevent statistical bias resulting from data overflow from high-volume centers or operators. Furthermore, precise description of the operator characteristics as well center characteristics was recorded.

| Data collection
All centers were asked to complete a one-time site questionnaire consisting of three parts (a) description of the center, (b) operators characteristics (c) procedural setting (details of the questionnaire are provided in Appendix 2).
Data were collected using a web-based system with automatic validation algorithm.

| Statistical analysis
Continuous variables are presented as mean ± one SD, and categorical variables as frequencies. Continuous variables were compared using the Student's t-test, or nonparametric tests in case of non-normal distribution (tested with Kolmogorov-Smirnov test). Categorical variables were compared using the chi-square test. To calculate odds ratio (OR) a logistic regression model was used. A P-value of < .05 was considered statistically significant. Analysis was performed with SPSS v 20.0 (SPSS Inc., Chicago, Illinois).

| Procedural settings
The most frequently conducted procedure in the current study was In 275 cases (15%), fusion with an additional image modality was employed. One hundred and ninety-six cases (11%) were conducted under general anesthesia.
Detailed case characteristic is summarized in Table 3.
The correlation between applied dose of fluoroscopy and time of exposure was poor, although statistically significant (R 2 = .37, P < .001).
The use of fluoroscopy is presented in Figure 1.

| Factors associated with reduced use of fluoroscopy
Procedures in lower quartile of DAP were characterized by values <52 cGy*cm 2 for DP, < 110 cGy*cm 2 for SVT cases, <325 cGy*cm 2 for AF ablation and <972 cGy*cm 2 for VT procedures.
In univariate analysis, female gender was significantly associated with a reduced dose of fluoroscopy (OR 1. per one additional procedure, 95% CI 1.000-1.001, P = .002).
The results of multivariate analysis are presented in Figure 2.

| Importance of fluoroscopy dose reduction
Fluoroscopy time (min ± SD) 12 ± 13 Dose area product (cGy*cm2 ± SD) 1236 ± 2295 Procedures without use of fluoroscopy, n (%) 125 (7%) Type of 3D mapping system, n (%) X-ray C-arm 96 (5) cardiology is responsible for about 40% of the entire exposure from all medical sources, as a consequence of widespread availability of X-raybased imaging techniques. [6][7][8][9] Cardiac use of fluoroscopy almost never reaches the threshold for deterministic radiation injury, but it gives an additional lifetime risk of fatal and nonfatal cancers thus the amount of used radiation should be as low as reasonably achievable. 10 A cornerstone of enhanced radiation safety is optimization, that is, reducing as much as possible the use of X-rays for a given technique. [6][7][8][9]11

| Different units of measurement
As the awareness of the relevance of fluoroscopy gets higher and higher there is a need for a more precise description of radiation exposure. Even these days many authors use the description of "fluoroscopy time" as a measure of radiation related to ablation procedures. However, this may be misleading as there are many other factors that influence radiation exposure such as frame rate, radiation dose per pulse, collimation-each of which will determine effective dose to a far greater degree than exposure time. 12,13 In line with this statement, our registry also showed only a weak correlation between fluoroscopy time and dose. Because dose area product is readily available from all imaging system vendors, and because it provides an exposure dose that linearly correlates with true estimated effective biological dose, it is probably a far better parameter for comparing radiation exposure in this and other datasets. 14

| Dose of fluoroscopy-low, near zero, and zero
The goal of reducing exposure to ionizing radiation as much as possible is well accepted. Considering the stochastic effects of radiation it is not likely that there will ever be a recommendation for a radiation dose that is considered "safe," as very low doses may still be harmful.
Thus, current best practice is to get close to ("near zero") or ideally achieve zero fluoroscopy. After numerous single-center experience papers and feasibility studies the first prospective randomized trial (NO-PARTY trial) showed that a minimally fluoroscopic approach significantly reduces radiation exposure during electrophysiology procedures while it does not compromise procedure time and does not affect safety and efficacy. 15 Obviously, "near zero" and zero fluoroscopy involves an expense both in terms of time (learning) as well as equipment, as additional imaging modalities such as electroanatomical mapping systems or intracardiac echocardiography (ICE) are typically used in these cases.  17 Moreover, in our registry 7% of all procedures were performed without the use of any fluoroscopy. Multivariate analysis showed high volume centers and use of monoplane systems to be independent predictors of lower DAP values which is likely to be attributable to available expertise and availability of mapping systems in those centers. Of particular note is that female gender is the only independent predictor of low exposure on the operator level. The authors therefore speculate that a personal motivation for radiation reduction seems to be a significant driver in achieving low fluoroscopy exposure. 18

| Limitations
The main limitation of our dataset is its observational nature. However, real-life registries of consecutive patients at the level of individual operators have the potential to provide insights into contemporary practice across different regions with different practices, regulatory requirements, and resources. All data were prospectively collected using the same method in all participating centers, but some datapoints were incomplete for a minority of procedures.

| CONCLUSIONS
This real-life registry of fluoroscopy usage across Europe shows that contemporary practice and use of modern mapping technology results in average exposure doses below previously reported values. Furthermore, gender and thus probably personal motivation is independently associated with lower radiation exposure.