The Hitchhiker’s Guide to Zero Fluoroscopy Catheter Ablation

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

EP Review

The Hitchhiker’s Guide to Zero Fluoroscopy Catheter Ablation

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

February 2024

© 2024 HMP Global. All Rights Reserved.

Any views and opinions expressed are those of the author(s) and/or participants and do not necessarily reflect the views, policy, or position of EP Lab Digest or HMP Global, their employees, and affiliates.

EP LAB DIGEST. 2024;24(2):1,12-17.

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.

Mitra Catheter Ablation Figure 1 — Figure 1. Respiratory gating of the ICE catheter in the hepatic vein just below the diaphragm (the patient is already fully heparinized with an activated clotting time >300 seconds as soon as sheaths are placed in groin).

Mitra Catheter Ablation Figure 2 — Figure 2. Initial ICE sweep of right atrium, right atrial appendage, tricuspid valve, right ventricle, and aortic root. LA and esophagus.

Mitra Catheter Ablation Figure 3 — Figure 3. Creation of CartoSound map of the LA and esophageal delineation.

Mitra Catheter Ablation Figure 4 — Figure 4. Identifying CS os, left atrial appendage, and fossa ovalis.

Mitra Catheter Ablation Figure 5 — Figure 5. Posterior LA with esophagus.

Mitra Catheter Ablation Figure 6 — Figure 6. Advancing ablation catheter with contact force for same navigation from the inferior vena cava to the right atrium and creation of the inferior and superior vena cava, right atrium, and CS volumetric map. Contact force also used to safely advance catheter within CS, creating a hybrid right and LA map.

Mitra Catheter Ablation Figure 7 — Figure 7. Placing the CS catheter.

Mitra Catheter Ablation Figure 8 — Figure 8. Using ablation catheter to position Vizigo sheath against the fossa ovalis to prepare for transseptal puncture.

Mitra Catheter Ablation Figure 9 — Figure 9. Tenting of the fossa ovalis with the Vizigo sheath and then advancing the dilator with the radiofrequency needle to perform transseptal puncture with dilator, but the Vizigo is not able to be advanced.

Mitra Catheter Ablation Figure 10 — Figure 10. Dilator removed from Vizigo. Ablation catheter, which passes through transseptal into the LA as a rail, is used to advance the Vizigo into the LA.

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.

Mitra Catheter Ablation Figure 11A — Figure 11a. Using Octaray (Biosense Webster, Inc, a Johnson & Johnson company) to create voltage and geometric map of the LA.

Mitra Catheter Ablation Figure 11B — Figure 11b. Posterior view of the LA showing the esophagus and the Pentaray in a right middle vein.

Mitra Catheter Ablation Figure 12A — Figure 12a. Creation of a 4-chamber sound map of the heart, including the aortic root and ascending aorta, in preparation for retrograde cannulation of the LV.

Mitra Catheter Ablation Figure 12B — Figure 12b. Using contact force and visualization of the ablation catheter shaft to safely come from the abdominal and thoracic aorta to descend into the aortic arch for retrograde cannulation in the RAO and LAO projections.

Mitra Catheter Ablation Figure 13A — Figure 13a. Spin of zero fluoroscopy 4-chamber geometry in a case of ischemic VT ablation.

Mitra Catheter Ablation Figure 13B — Figure 13b. Activation map of VT in a zero-fluoroscopy case of ischemic VT ablation showing a figure-of-8 circuit with slowing along the edges and entering the isthmus region of slowest conduction in the presence of a large anteroapical infarction. The ECG pictured below is post ablation.

Mitra Catheter Ablation Figure 13C — Figure 13c. Pentaray signal from regions of isthmus and slow conduction with mid-diastolic signals seen on electrodes 1-2 and 17-18 and exit site 9-10.

Mitra Catheter Ablation Figure 14 — Figure 14. Incessant amiodarone-resistant LA tachycardia occurring 1 month post ablation for persistent AF due to incomplete posterior wall ablation with electrograms on Pentaray showing slow conduction in region of patchy low voltage.

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.

Mitra Catheter Ablation Figure 15A — Figure 15a. Zero fluoroscopy 4-chamber spin of heart and aorta for a case of idiopathic PVCs from between the left and right coronary cusp. One can appreciate the proximity to the septal side of the right ventricular outflow tract.

Mitra Catheter Ablation Figure 15B — Figure 15b. Pace map of idiopathic PVCs from between the right and left coronary cusps.

Mitra Catheter Ablation Figure 15C — Figure 15c. Bipolar and unipolar signals during ventricular premature depolarization from the successful site in the aortic root.

Mitra Catheter Ablation Figure 15D — Figure 15d. Distance of 8.8 mm from the successful aortic root ablation site and earliest right ventricular outflow tract sites.

Mitra Catheter Ablation Figure 16A — Figure 16a. CS electrograms from the anterior interventricular vein (at left) vs the LV (at right). Despite small unipolar R wave in CS, this was the successful site for ablation (20W) while only suppression achieved from LV (50W) with half-normal saline.

Mitra Catheter Ablation Figure 16B — Figure 16b. Distance between the CS and LV endocardial lesions was 9.6 mm.

Mitra Catheter Ablation Figure 17 — Figure 17. Use of clipping plane to define region of slow pathway along right interatrial septum and region anterior to the CS os and 15.9 mm from compact AV node (yellow circles).

Mitra Catheter Ablation Figure 18 — Figure 18. Reduction in EP lab nurse’s radiation badge despite increase in ablation volume within 1 year of initiating zero fluoroscopy program.

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.

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