The Hitchhiker’s Guide to Zero Fluoroscopy Catheter Ablation
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EP LAB DIGEST. 2024;24(2):1,12-17.
Raman Mitra, MD, PhD, Director of Electrophysiology, North Shore University Hospital, Associate Professor of Cardiology, Zucker School of Medicine and Northwell-Hofstra, Manhasset, New York
Fluoroscopy has been the backbone underlying modern electrophysiology (EP) ablation procedures to safely navigate and localize catheters within cardiac structures and blood vessels. All operators performing catheter-based procedures are required to have training in radiation safety.
According to the 2018 ACC/HRS/NASCI/SCAI/SCCT expert consensus document on optimal use of ionizing radiation in cardiovascular imaging, catheter ablation is associated with a wide range of radiation dose exposure, ranging from 1-25 mSv.1 This is dependent on multiple factors, including operator experience, procedural technique, type of arrhythmia, available equipment, and patient body habitus. Patients, operators, and staff are all at variable degrees of risk from radiation exposure. The patient may be exposed to additional radiation when considering any periprocedural testing such as cardiac computed tomography, which may add another 10-30 mSv. For the operator and staff, protection is typically provided by radiation shields, lead vests, aprons, thyroid collars, and radiation goggles. Wearing protective lead outerwear over many years, however, is associated with spinal problems among interventional cardiologists, electrophysiologists, and staff. This has been mitigated partly by the implementation of large, suspended body shields.
A guiding principle of radiation safety is “as low as reasonably achievable (ALARA).”2 For patients, staff, and operators, the goal of ALARA is not fixed, but rather, movable towards “absolute zero” due to advances in technology. However, this should not be at the cost of procedural success or safety. Since 2015, we have adopted zero-fluoroscopy ablation for all endovascular EP procedures, including atrial fibrillation (AF) and ventricular tachycardia (VT) ablation. In this article, we will review some of the advances in technology that have permitted this paradigm shift in our approach to endocardial catheter ablation, as well as share examples and technical tips. We hope to demonstrate that these innovations have allowed for catheter mapping and ablation in a safer and more effective manner, and that the elimination of fluoroscopy was not the goal but rather the natural consequence of using these newer technologies. It should be noted that electrophysiologists should never hesitate to don lead and use fluoroscopy if there are access or catheter advancement issues.
Considerations for Zero-Fluoroscopy Ablation
Electroanatomic mapping (EAM) was the first technological advance that allowed significant fluoroscopy reduction by allowing the creation of endocardial geometry and catheter localization.3 Examples include the Carto (Biosense Webster, Inc) and EnSite NavX (Abbott) systems. Biosense catheter localization is achieved through a proprietary, magnet-embedded mapping or ablation catheter that perturbs a low magnetic field generated by a triangular magnetic array placed below the patient. EnSite NavX uses perturbation of an electric field by the electrodes of any catheter (impedance-based) created by patches placed on the patient’s chest, and is therefore, an open-source system. The latest versions of each system now combine both approaches. The Rhythmia Mapping System (Boston Scientific) is magnetic and impedance based, using a multielectrode basket catheter to create high-density maps.
In their current iteration, each of these systems allows for creation of endocardial contours and geometry as well as high-density voltage and activation maps of the heart. From a safety standpoint, certain concerns remain with EAM systems alone in the absence of fluoroscopy:
- Safe navigation from the vascular access site to the heart, particularly in cases of vascular anomalies or tortuosity to avoid inadvertent vessel perforation;
- Prevention of cardiac perforation with the diagnostic, mapping, or ablation catheter until an accurate anatomic map is created;
- Safe transseptal or retrograde access.
The first concern can be obviated by using vascular ultrasound to guide access and either a magnetic or impedance system to advance catheters. Longer sheaths advanced over guide wires may also decrease the risk of intraperitoneal perforation by catheters. However, there will be rare instances when contrast and fluoroscopy will be required to safely advance sheaths or catheters if vascular tortuosity or obstruction is present.
Even with an EAM system, however, the need for fluoroscopy was critical to safely obtain access to the left side of the heart via either transseptal access or retrograde aortic cannulation. The initial availability of radial/rotational intracardiac echocardiography (ICE) in 1999, followed by phased array ICE in 2002, eventually helped to overcome concerns about safe transseptal or retrograde access.4
Electroanatomic catheters with contact force capabilities also facilitated safe advancement of catheters from the vascular access point to the heart, as well as within the heart, and appear to be associated with less risk of perforation.5
Much of the early work on fluoroscopy reduction during EP procedures came from the pediatric literature.6-12 The early attempts to reduce fluoroscopy during ablation focused on right-sided arrhythmias such as atrial flutter or atrioventricular nodal reentry, which could be performed with an EAM system alone. The first description of zero-fluoroscopy ablation for AF in adults was reported by Ferguson et al. One of the earliest adopters of zero-fluoroscopy ablation for atrial and ventricular arrhythmias was Razminia et al.13,14 Subsequently, there have been several publications on a zero-fluoroscopy approach for atrial arrhythmias as well as the ability to use this approach during pregnancy.15-17
The Table chronologically lists the significant technological advances that have allowed for not only reduced fluoroscopy but also zero-fluoroscopy ablation. Most of our cases have been with the Carto system; since 2015, we have performed more than 99% of cases without fluoroscopy and without wearing lead. The availability of the Vizigo has further facilitated the zero-fluoroscopy workflow; Vizigo received approval for a zero-fluoroscopy workflow from the FDA in August 2023.18
Examples From Our Experience
The accompanying videos and figures lay out a step-by-step approach to performing zero-fluoroscopy ablation for atrial and ventricular arrhythmias. These examples from our experience should help those wishing to perform these procedures understand the workflow used to perform zero-fluoroscopy ablation for AF and VT. It should be noted that the FDA approval for zero-fluoroscopy approach mentions only AF ablation.
Figures/Videos 1-10 demonstrate the process of navigation from groin access to the heart to create biatrial geometry, localize the esophagus, and gain transseptal access. Many currently practicing electrophysiologists use very little fluoroscopy to map and ablate the left atrium (LA) with the current multielectrode catheters and EAM systems once transseptal access is obtained.
Video 11a and Figure 11b show the voltage map of the LA as well as the pliability of the Pentaray spline catheter to adapt its shape to vessels (a right middle vein) and the endocardium.
Videos 12a-b illustrate the technique for retrograde aortic access without fluoroscopy achieved by merging the ascending aortic sound map with the EAM map created with the catheter as it comes around the arch. The sound map also allows visualization of any plaque that may be present in the aortic root that can be tagged.
Videos 13a-b and Figure 13c demomstrate a zero fluoroscopic ischemic, incessant, hemodynamically tolerated VT ablation and creation of a 4-chamber EAM/sound map and a figure-of-8 VT in a patient with a large anteroapical infarction along with the electrogram resolution afforded by small 1-mm electrodes of the Pentaray in the isthmus corridor.
Video 14 shows a microreentrant left posterior wall tachycardia occurring after previous pulmonary vein isolation and posterior roof line. Note the long mid-diastolic, low-amplitude electrograms on the D spline.
Video 15a and Figures 15b-d show ablation of premature ventricular contractions (PVCs) arising from the aortic coronary cusps, initially attempted from the posterior right ventricular outflow tract. The pace maps and very low amplitude fractionated electrograms from the ablation site are shown as well.
Figures 16a-b show a case of an idiopathic PVC from the anterior interventricular vein region that required ablation from the CS after ablation from the LV endocardium led to suppression but not elimination. Presystolic signals from both the left ventricle (LV) and coronary sinus (CS) are shown, and despite the unipolar signal from the CS having a small R wave while the LV had a qS, the pace map was better from the CS and led to successful ablation. This distance from the center of the CS to the LV lesions is 9.6 mm.
Figure 17 illustrates the usefulness of using the clipping plane in the right atrium to see the septal wall and CS os for slow pathway ablation. Both RAO and LAO views are shown and the distance from the successful slow pathway lesions and the AV node (yellow) was 15.9 mm.
Figure 18 is a striking example of the reduction of fluoroscopy exposure to one of our staff members when we adopted the zero-fluoroscopy workflow between 2014 to 2015, despite a significant increase in ablation volume.
Summary
The videos and figures included here should be beneficial in helping to reduce or eliminate fluoroscopy during complex ablations. It is important to note that there is a learning curve and one should not hesitate to use fluoroscopy to safely and effectively perform procedures based on the operator’s comfort. Despite the sophisticated mapping and ablation tools currently available, one should not base ablation strategy primarily on color maps, but rather on a thorough understanding of the electrograms, sampling windows, and conduction properties from which they are derived. The additional use of ICE for anatomic confirmation further enhances efficacy and safety.
Acknowledgment. We would like to thank several colleagues with whom we have shared this journey, including James Ferguson, MD; Amit Thosani, MD; Paul Zei, MD; Jose Osorio, MD; Brett Gidney, MD; Tariq Salam, MD; and Mansour Razminia, MD. We would also like to thank Elizabeth Robinson and Mahum Siddiqui from Biosense Webster for their help in capturing the figures and videos.
Disclosure: The author has completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest, and reports no conflicts of interest regarding the content herein.
References
1. Hirshfeld JW Jr, Ferrari VA, Bengel FM, et al. 2018 ACC/HRS/NASCI/SCAI/SCCT expert consensus document on optimal use of ionizing radiation in cardiovascular imaging-best practices for safety and effectiveness, part 2: radiological equipment operation, dose-sparing methodologies, patient and medical personnel protection: a report of the American College of Cardiology Task Force on Expert Consensus Decision Pathways. J Am Coll Cardiol. 2018;71(24):2829-2855. doi:10.1016/j.jacc.2018.02.018
2. National Council on Radiation Protection and Measurements. Report No. 107. Implementation of the Principle of as Low as Reasonably Achievable (ALARA) for Medical and Dental Personnel; 1990. NCRP Publications.
3. Gepstein L, Hayam G, Ben-Haim SA. A novel method for nonfluoroscopic catheter-based electroanatomical mapping of the heart in vitro and in vivo accuracy results. Circulation. 1997;95(6):1611-1622. doi:10.1161/01.CIR.95.6.1611
4. Packer D, Stevens C, Curley M, et al. Intracardiac phased-array imaging: methods and initial clinical experience with high resolution, under blood visualization. J Am Coll Cardiol. 2002:39(3):509-516. doi:10.1016/s0735-1097(01)01764-8
5. Akca F, Janse P, Theuns DA, Szili-Torok T. A prospective study on safety of catheter ablation procedures: contact force guided ablation could reduce the risk of cardiac perforation. Int J Cardiol. 2015;179:441-448. doi:10.1016/j.ijcard.2014.11.105
6. Drago F, Silvetti MS, Di Pino A, et al. Exclusion of fluoroscopy during ablation treatment of right accessory pathway in children. J Cardiovasc Electrophysiol. 2002;13(8):778-782. doi:10.1046/j.1540-8167.2002.00778.x
7. Smith G, Clark JM. Elimination of fluoroscopy use in a pediatric electrophysiology laboratory utilizing three-dimensional mapping. Pacing Clin Electrophysiol. 2007;30(4):510-518. doi:10.1111/j.1540-8159.2007.00701.x
8. Tuzcu V. A nonfluoroscopic approach for electrophysiology and catheter ablation procedures using a three-dimensional navigation system. Pacing Clin Electrophysiol. 2007;30(4):519-525. doi:10.1111/j.1540-8159.2007.00702.x
9. Clark J, Bockoven JR, Lane J, Patel CR, Smith G. Use of three-dimensional catheter guidance and transesophageal echocardiography to eliminate fluoroscopy in catheter ablation of left-sided accessory pathways. Pacing Clin Electrophysiol. 2008;31(3):283-289. doi:10.1111/j.1540-8159.2008.00987.x
10. Miyake CY, Mah DY, Atallah J, et al. Nonfluoroscopic imaging systems reduce radiation exposure in children undergoing ablation of supraventricular tachycardia. Heart Rhythm. 2011;8(4):519-525. doi:10.1016/j.hrthm.2010.12.022
11. Papagiannis J, Avramidis D, Alexopoulos C, Kirvassilis G. Radiofrequency ablation of accessory pathways in children and congenital heart disease patients: impact of a nonfluoroscopic navigation system. Pacing Clin Electrophysiol. 2011;34(10):1288-1396. doi:10.1111/j.1540-8159.2011.03170.x
12. Vinocur J. Our road to zero radiation catheter ablation in pediatric and congenital heart disease. EP Lab Digest. 2020:20(5):40-43.
13. Ferguson JD, Helms A, Mangrum JM, et al. Catheter ablation of atrial fibrillation without fluoroscopy using intracardiac echocardiography and electroanatomic mapping. Circ Arrhythm Electrophysiol. 2009;2(6):611-619. doi:10.1161/CIRCEP.109.872093
14. Razminia M, Willoughby MC, Demo H, et al. Fluoroless catheter ablation of cardiac arrhythmias: a 5-year experience. Pacing Clin Electrophysiol. 2017;40(4):425-433. doi:10.1111/pace.13038
15. Lerman BB, Markowitz SM, Liu CF, et al. Fluoroless catheter ablation of atrial fibrillation. Heart Rhythm. 2017;14(6):928-934. doi:10.1016/j.hrthm.2017.02.016
16. Percell RL. The SANS FLUORO approach to ablation. EP Lab Digest. 2019;19(3):33-35.
17. You J, Pagan E, Mitra R. Comparison of minimal versus zero-fluoroscopic catheter ablation in gestational supraventricular arrhythmias. J Interv Card Electrophysiol. 2023;66(6):1423-1429. doi:10.1007/s10840-022-01444-1
18. Biosense Webster receives FDA approval for multiple atrial fibrillation ablation products to be used in a workflow without fluoroscopy. Biosense Webster. Published August 4, 2023. Accessed December 1, 2023. https://www.jnj.com/biosense-webster-receives-fda-approval-for-multiple-atrial-fibrillation-ablation-products-to-be-used-in-a-workflow-without-fluoroscopy#:~:text=IRVINE%2C%20CA%20%E2%80%93%20August%204%2C,the%20U.S.%20Food%20and%20Drug
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