Catheter ablation (CA) procedures are traditionally performed solely under fluoroscopic guidance but the development of three-dimensional (3D) electroanatomic mapping (EAM) systems has led to a dramatic decrease or even a complete abandonment of fluoroscopy during the last decade.¹² The current best practice is to get close to "near-zero" (NZ) or ideally achieve "zero fluoroscopy" (ZF) at the even expense of a longer procedure time.³⁴⁵⁶ With this in regard, performing ZF CA should therefore be an objective in all electrophysiology labs, considering that safety and efficacy still need to be demonstrated with robust data.⁶

Radiofrequency CA of an outflow tract ventricular arrhythmia (VA) that originates from the aortic coronary cusps (CC) can be challenging.⁷

Coronary angiography has traditionally been recommended before and during aortic CC CA to make sure there is a safe distance to coronary ostia.⁴⁸⁹¹⁰ Serious rare complications such as aortic regurgitation or aortic leaflet perforation following CA are also likely, although reluctantly reported.¹¹¹² Acute and chronic left main artery occlusions have been reported as a complication of CA of idiopathic left VT.¹³¹⁴ Therefore, it requires greater expertise and more imaging modalities.⁴¹⁵ Indeed, the intracardiac echocardiography (ICE) have been standard imaging method to confirm adequate tissue apposition of the ablation catheter and permits through examination of the anatomical structures of the heart while avoiding coronary angiography and limiting risk.¹⁶¹⁷ However, the health insurance agencies do not cover the costs of ICE catheters in most countries therefore, high costs remain a limitation of the use of ICE.¹⁸ In our center, whereas the ablation of aortic CC VAs have been performed from superior to the aortic sinus of valsalva [above-valve approach (AVA)] under limited fluoroscopy (NF) to evaluate the coronary ostia despite 3D-EAM guidance; the ZF ablation have been preferred when the CC ablations have been performed by the below-valve approach (BVA) based on operator’s discretion on a case-by-case basis. Since the true junction of these cusps is located approximately 1.5 cm above the base of either CC,¹⁹ a site where ablation catheter would not be expected to contact the aorta. The purpose of this study was to evaluate outcomes of ZF ablation of aortic CC VAs by the BVA and to find the anatomical predictors of limited fluoroscopy need in aortic CC VAs.

This is a single-center study describing outcomes of 57 patients with symptomatic and, either drug-refractory (n = 55) or drugintolerant (n = 2) VAs [ventricular extrasystoles (VESs) and/or ventricular tachycardia (VT)] with the origin at the aortic CCs, which were selected CA between January 2019 and January 2021. All cases where ZF ablation was on a defined region specifically inferior to the aortic sinus of valsalva have been included in the BVA group, whereas the patients who need fluoroscopy at any level during the procedure and/or all supravalvular CC ablations with NF due to coronary delineation have been included in the AVA group as a control arm.

Baseline data included demographic characteristics, cardiac history, procedure details, echocardiography, and 24-hour Holter monitoring. Idiopathic VA was diagnosed in patients without structural heart disease (SHD), based on history, typical clinical features, echocardiography, exercise stress testing, cardiac catheterization, and cardiac magnetic resonance imaging when needed. All antiarrhythmic drugs were discontinued for at least five half-lives before the procedure. Clinical features and procedural outcomes were evaluated in all cases.

Left ventricular outflow tract sites were mapped via a retrograde aortic approach. The origins of VESs/VT were classified as left CC (LCC), right CC (RCC), LCC and RCC junction (LCC-RCC commissure), or non-coronary cusp (NCC). Mapping methods included simple maps with aortic cusp or aortic root contours, activation mapping with unipolar/bipolar recordings, and pace mapping using the PASO® module. We used the catheter inversion technique as a BVA defined by Yamada et al,²⁰²¹ in which the tip of the looped mapping catheter can reach underneath the aortic CCs by pulling up the catheter (Figures 1 and 2). When the loop is released appropriately, a good contact of the tip of the mapping catheter on the tissue in this region can be obtained without any disturbance from the movements of the aortic valves. When the looped catheter is rotated, the tip of the mapping catheter can be positioned underneath any aortic CCs.²¹

The medical staff using the ZF approach did not wear heavy protective apparel. Intravenous heparin was administered to maintain an activated clotting time of ≥300 s during procedures. The retroaortic route represents the first‐line access route for arrhythmias arising from the peri‐aortic region including the CCs or aorto‐mitral continuity.²² In our institution, we use a stepwise approach to navigate tortuous peripheral vasculature and arcus aorta. An initial approach involves advancing a soft angled guidewire to the descending aorta followed by a long sheath then a 3.5-mm externally irrigated ablation catheter (Thermocool SF, Biosense-Webster, Inc., Diamond Bar, CA) was advanced into the descending aorta under EAM system guidance (CARTO 3, Biosense-Webster, Inc., Diamond Bar, CA). In cases where advancing the wire or sheath is challenging, stiffer wires are used to navigate the vessel. Any difficulties in catheter advancement were overcome with a geometric acquisition of the trajectory of the catheter through the arterial system. The position of the ablation catheter tip within the aortic cusps was confirmed using several techniques (i.e., inability to move further through the aortic valve and to bend the catheter to the mitral annulus).⁴ No simultaneous left coronary angiography and coronary sinus angiography were performed in the BVA group; however, in case of suspected complication or difficulties of catheter movement/mapping, radiation use was left to the decision of the operator; and these patients were evaluated under the NF group.

Standard ventricular stimulation was performed to induce VT in idiopathic VT cases. Isoproterenol infusion up to 5 mcg/min was used if necessary. Activation mapping was performed in all cases. The earliest activation site was determined by the longest ventricular signal to QRS interval measured at any of aortic CCs. If myocardial sites exhibiting the earliest bipolar activity or local unipolar QS pattern were confirmed to be BVA, radiofrequency-energy was delivered at locations with an early activity preceding the QRS onset for ≥25 msec during the VA. Irrigated CA applications were set at 30W at 42°C. Procedure time was defined as the duration from the 1st puncture of the skin to the complete removal of the catheters.

The acute procedural success of CA was defined as the complete absence of spontaneous VES/VT for more than 30 minutes following the last application, non-inducibility after isoproterenol infusion, and the complete electrophysiologic study using atrial incremental pacing, and ventricular and atrial programmed pacing up to 3 extra stimuli.

The acute- and short-term follow-up was set at the time of ablation procedure and 1 month after, respectively. Treatment success was referred to as an 80% or higher post ablation decrease in VES burden. Furthermore, all patients underwent a transthoracic echocardiogram immediately after the procedure in the electrophysiology laboratory and 24-hour after the procedure to rule out pericardial effusion.

Statistical analysis

Continuous data are described as the mean ± standard deviation, whereas categorical data are expressed as numbers and percentages. All analyses were performed using Statistical Package for the Social Sciences (SPSS) version 20.0 (IBM Inc., Armonk, NY). All tests were 2-sided, and a P value of 0.05 was considered statistically significant.

A total of 23 cases with BVA were included (48 ± 14 years; 62% male; mean ejection fraction, 58 ± 9%). Since two (9%) patients required limited fluoroscopy due to the inability to advance the catheter from descending aorta to ascending aorta despite long sheath use, a total of 21 patients evaluated in the BVA group. Among 21 patients consecutively enrolled in this study, 19 (90%) patients were referred for CA of PVC and 2 (10%) patients for ablation of idiopathic VT. Ablation was done for high PVC burden (>10%; mean 17 ± 2%) and presence of symptoms (94%) or left ventricular ejection fraction less than 50% (19%). All patients had a left bundle branch block morphology, inferior axis with pointed QRS in the inferior leads and early transition in the precordial leads, mostly in V2 or V3.²³²⁴

Ablation was acutely successful in 20 of 21 (98%) cases using ZF in the BVA group. In one patient, repeat ablation in the same region resulted in durable suppression in the following day. After 1 month, success was noted in 19 of 21 (90%). The use of ZF was achieved in 37% of all aortic VAs, but 91% of all BVA cases, particularly in the LCC-RCC commissure region [14/16 (88%)]. Thirty-two patients in the LCC group and 2 patients in the LCC-RCC commissure group needed supravalvular AVA to achieve acute success. The mean procedure time was 100 ± 20 min.

There were no complications potentially associated with the proximity of the ablation catheter to the aortic root, coronary ostia, and conduction system. There was a single case of the post-ablation pseudoaneurysm, which was treated surgically.

Our trial suggested that the technique of catheter inversion with the retrograde transaortic route by BVA might be useful particularly in ZF ablation of the LCC-RCC commissure VAs. The ZF ablation significantly reduces ablation time and radiation dose without compromising success, complication, and recurrence rates,²⁵²⁶ and can be performed after an adequate learning curve.³²⁷²⁸ An understanding of the anatomic relationship between the aortic valvar leaflets and their supporting aortic sinuses, coronary vessels, pulmonary arterial root, right and left ventricular outflow tracts is essential for successful treatment of arrhythmias arising from this region.²⁹ There are important interrelationships between aortic sinuses and valvar leaflets, supporting left ventricular structures that produce the three fibrous interleaflet triangles.³⁰ The juxtaposition of aortic valvar leaflet insertion into the aortic root and the crescents of myocardial tissue incorporated within the aortic sinuses have implications for mapping and ablation above and below the aortic valve leaflets.²⁹ The site of successful ablation of aortic cusp VAs has been confirmed to be above the aortic valve plane in most studies.²³³¹³² The most common reason for using fluoroscopy was anatomic neighboring of coronary ostia in the AVA group; therefore, the catheter inversion technique via BVA defined by Yamada et al.,²⁰²¹ in which the tip of the looped mapping catheter can reach underneath the aortic cusps by pulling up the catheter has been gained interest. Since the true junction of these cusps is located approximately 1 cm above the base of either cusp,¹⁹ a site where the ablation catheter would not be expected to contact the aorta. Since the anatomy of the right-left aortic interleaflet triangle is highlighted as an anatomical vantage point from the endocardial anterior left ventricular ostium²⁴ and summit³³ to eliminate these refractory arrhythmias. It is also most probable that the LCC-RCC VA origin is below the triangular space where the left and right cusps join.²⁴²⁹³¹ The ablation of the LCC-RCC commissure site would be difficult within the aorta itself unless the catheter is advanced below the valve.²⁹³¹ Furthermore, the coronary ostia typically are seen 1.5 cm above the aortic annulus, and the BVA might provide safer ablation due to the anatomic distance between the leaflet and coronary ostia.³⁴ Some groups prefer the BVA by transeptal route;²⁹³⁵ however, reversed S curve of the ablation catheter often has to be created to reach the region.³⁵ Therefore, the BVA might be more appropriate way to reach that area.²¹

The risk of valvular injuries during aortic retrograde approaches potentially correlates with the procedure duration, the number of RF applications, and passages through the aortic valve.¹² In any case, it is noteworthy that there were no major complications experienced during this study; however, care should still be taken to avoid slipping above the cusps, in which case one may approximate the ostium of the left main artery.³⁶ Moving catheters into sensitive regions (e.g., left main or right coronary artery during a retrograde aortic approach), should, in case of uncertainty, always be guided by real-time fluoroscopy.³⁷ The retrograde approach may be associated with an increased risk of brain emboli³⁸ or aortic dissection39 despite we did not see neurological events related to the retrograde approach in our small series.

This study presents several limitations. It is not a randomized trial and the population size is relatively small. It is focused on describing our approach; it is an observational study without a true control group. As we did not initially attempt ablation from the AVA, a comparison cannot be made between the BVA and AVA. It, therefore, does not have the statistical power to conclude the safety or efficacy of first-line BVA.

Whereas aortic root VAs can be readily ablated with success from either above or below the valvular leaflets,³⁶ the BVA approach might be preferable in the absence of ICE particularly for ZF ablation of LCC-RCC commissure VAs.