Ablation with zero‐fluoroscopy of premature ventricular complexes from aortic sinus cusps: A single‐center experience

Abstract Background Catheter ablation of premature ventricular complexes from aortic sinus cusps (ASC‐PVC) is a complex procedure that conventionally requires coronary catheterization (CC) to localize coronary artery ostium (CAO). Little published information is available on the mapping and ablation with zero‐fluoroscopy (ZF) of ASC‐PVC. The aim of the study was to determine the efficacy and safety of ASC‐PVC ablation with a ZF approach guided by 3D intracardiac echocardiography integration in the electroanatomical mapping system (ICE 3D‐EAM). Methods This observational study included one patient cohort treated conventionally and another treated with ICE 3D‐EAM‐guided ZF ablation. Clinical, efficacy, and safety outcomes were evaluated acutely and at 3 months follow‐up. Results The study included 21 patients with ASC‐PVC: 10 in the ZF group (age 49 ± 16 years, 60% males) and 11 in the control group (age 47 ± 15 years, 27% males). Fluoroscopy was not required for any patient in the ZF group. Acute success was obtained in 80% of the ZF group vs 55% of the control group (P = .36). The recurrence rate was 30% in the ZF group vs 27% in the control group (P = 1). One nonsevere complication was observed in the ZF group (P = .48). Conclusions ZF catheter ablation of ASC‐PVC guided by ICE 3D‐EAM is feasible, effective, and safe.


| INTRODUC TI ON
Premature ventricular complexes (PVC) frequently originate from aortic sinus cusps (ASC-PVC), commonly in patients with no structural cardiovascular disease. 1 Their ablation is challenging due to their proximity to coronary artery ostium (CAO). [2][3][4][5] Coronary catheterization (CC) has conventionally been used to avoid complications during ablation and evaluate the distance from CAO. Over the past few years, there has been an increase in the implementation of zero-fluoroscopy (ZF) ablation guided by electroanatomical mapping (EAM) systems and imaging techniques. [6][7][8] However, little information is available on the outcomes of ablation with ZF in patients with ASC-PVC.
The objective of this study was to compare safety and efficacy outcomes between patients with ASC-PVC treated with ZF ablation guided by 3D integration of intracardiac echocardiography images in the EAM (ICE 3D-EAM) and those treated with the conventional approach.

| Study population, design, and patient selection
This observational, retrospective, and single-center study consecutively recruited patients undergoing ASC-PVC ablation at our center.
Among 37 patients who underwent 3D ICE-EAM-guided PVC ablation with ZF between April 2019 and September 2020, 10 (27%) with origin in ASC were enrolled in the ZF group. Among 56 patients with PVC who underwent a conventional approach between July 2015 and March 2019, 11 (19.6%) with ASC-PVC who required fluoroscopy and CC but not ICE were enrolled in the control group. The study was approved by the local ethics committee, and all participants signed their informed consent.

| Study protocol and follow-up
The procedure was performed without general anesthesia after the suspension of antiarrhythmic drugs (AADs) for at least five half-lives. The ablation protocol for each group is detailed below.
All patients underwent electrophysiological study (EPS) with the LabSystem Pro™ recording system (Boston Scientific; bipolar filter 30-250 Hz, unipolar Filter: 1-250 Hz, electrocardiogram [ECG] filter 1-100 Hz; sweep speed: 100 mm/s). Two operators with experience in PVC ablations and ICE-guided procedures performed all interventions. Local ventricular activation time (LVAT) was measured from onset of bipolar electrogram (EGM) in the ablation or mapping catheter until onset of QRS. Pace-mapping was performed at 2 mA above of diastolic threshold and a pacing cycle length of 600 ms After accessing the arterial circulation, unfractionated heparin was administered to maintain an activation clotting time >250 s. Success of the procedure was defined by complete PVC elimination baseline and after isoprenaline administration (0.5-2.0 mcg/ min) at the end of a 30 minute waiting period. All patients underwent 24 hours Holter monitoring at 3 months post-ablation. Success during the follow-up was defined by a reduction of >80% in baseline PVC density and by the absence of AADs to control symptoms not present before the ablation.
Data were gathered and analyzed on the baseline characteristics of the two groups, procedure-related safety and efficacy variables, and the presence/absence of recurrence during a 3 month follow-up period.

| Approach in the ZF group guided by ICE 3D-EAM
CARTO® navigation system (Biosense Webster) was used for all patients. All vascular accesses were obtained by ultrasound guidance.  For the passage of the aortic valve with the ablation catheter, we place the catheter posteriorly, in the noncoronary cusp (NCC) or between de NCC and the right coronary cusp (RCC), with the deflection (red label in the tip catheter) facing forward. After this, we deflect the catheter to form a pigtail while monitoring not to introduce the tip into the CAO, previously located and defined with CARTOSOUND®. Once we have made a pigtail with the ablation catheter the passage of the aortic valve is simple with torque and light pressure (video S1 in supplementary material).
The distance from ablation catheter tip to the corresponding CAO, as visualized by both ICE and navigation system, was measured using the previous 3D reconstruction ( Figure 2 and Figure 3). Radiofrequency (RF) was applied when the distance was >5 mm.
During ablation, the catheter tip was continuously monitored using the navigation system and real-time ICE visualization. When applied, RF was started at 20 W with contact of ≥5 g, upper temperature limit of 40℃, and irrigation flow of 17 mL/min. In cases of an adequate impedance drop (8-10 Ω) or PVC suppression, RF was increased to a maximum of 40 W and 180 seconds per application (video S2).
Postablation CC was not performed if no ST segment alterations or angina symptoms were observed during or after the ablation. with the EnSite Navx® system, according to the operator's criteria.

| Approach in the control group
From 2016 onward, the Thermocool Smart-Touch® catheter was used with the Carto3® system. The order of cardiac cavities mapping and the ablation criteria were the same as those for the ZF group.
After locating the earliest LVAT in ASC, CC was performed in the corresponding coronary artery (CA) to measure the distance between ablation catheter tip and CAO, using orthogonal planes and taking the width of the ablation catheter as reference (2.5 mm). CC was carried out in one or both CAs according to the operator's criteria. RF was applied when the distance was >5 mm in at least one angiographic projection. Application parameters were the same as for the ZF group.
During ablation, the position of the ablation catheter and the ST segment were monitored by fluoroscopy to evaluate CA involvement.
Postablation CC was not performed when no ST segment alterations or angina symptoms were observed during or after ablation.

| Statistical analysis
Continuous variables were expressed as mean ± standard deviation (SD) and categorical variables as absolute values and percentages.   Results of procedure-related variables are displayed in Table 1 for the ZF group and in Table S2 for the control group. In the ZF group, the mean procedure duration was 269 ± 56 minutes, ICE 3D-EAM reconstruction time was 45 ± 14 minutes, activation mapping time was 64 ± 29 minutes, RF time was 324 ± 211 seconds, and there was a mean of 6 ± 5 applications per patient. PVCs most frequently originated from the junction between RCC and LCC (60%), followed by the junction between NCC and RCC (30%), and the RCC (10%). Ablation was successful in 80% of cases. In the ZF group, the mean distance from the successful ablation spot was 15 ± 6 mm to right CAO and 22 ± 7 mm to left main CAO. No electrocardiographic alterations or clinical symptoms compatible with coronary involvement were observed in any patients, and there was no need for CC due to a poor visualization of CAO. One patient had a mild pericardial effusion after RF application, but no intervention was required and the procedure was not suspended.

| RE SULTS
Comparisons between the ZF and control groups are exhibited in Table 2. No significant between-group differences were observed in baseline characteristics or in the following procedure-related  No significant between-group difference was observed in rates of total acute success (80% in ZF group vs 55% in controls, P = .36) or success during 3 months follow-up (70% vs 73%, respectively, P = 1).

| D ISCUSS I ON
The main finding of this study was that ZF catheter ablation of ASC-PVC guided by ICE 3D-EAM is a safe procedure, is no less effective than the conventional approach, and offers a significant reduction in radiation time.
This approach was found to provide various advantages, includ- Transesophageal echocardiography has been proposed as an alternative approach but has only been described in a few isolated cases. 12 In addition, contrast injection through the ablation catheter has been proposed as a tool to visualize CAO, but the low flow of injected contrast limits the accuracy of CAO distance estimations. 13 The use of ICE to guide ASC-PVC ablation, as in the present study,  The feasibility of ablation procedures with ZF has been demonstrated in simple substrates such as supraventricular tachycardia or common atrial flutter. 6,7 They have reduced the exposure to radiation, which has been associated with acute and subacute skin lesions, oncological processes, cataracts, thyroid involvement, and other organ and system disorders. [15][16][17] Interventions in cardiac electrophysiology should follow the principle "as low as reasonably achievable" (ALARA), and the ZF approach has been reported to reduce the risk of cancer and mortality by 96% in comparison to conventional fluoroscopy. [18][19] The emergence of ICE and its 3D integration has enhanced the visualization of adjacent anatomical structures and improved the efficacy and safety of complex procedures. 20

| Study limitations
First of all, this study is limited by its retrospective and nonrandomized design and small sample size. On the one hand, the ZF ICE 3D-EAM procedures were done by experienced operators in this kind of interventions. These results may therefore not be directly replicable in other centers without enough ICE experience and further assessments are required for expanding these results. On the other hand, regarding origin classification of the ASC-PVC in the conventional group, some PVC were classified as LCC origin; however, there can be a mismatch between the real localization of the PVC in the exact site of the cusp using angiography. Therefore, PVC origin may have been cataloged as LCC when in reality its origin is closer to LCC-RCC. In addition, the ZF group did not include any patients with ASC-PVC exclusively originating from the LCC, who might possibly have a greater need for CC due to the closer proximity to CAO. However, ICE 3D-EAM offered a reliable and precise visualization of the LMCA ostium for evaluation of the safety distance. It should also be taken into account that 3 patients in the control group did not undergo ablation guided by contact force.
Finally, a more prolonged follow-up period is needed to evaluate long-term success rates.

| CON CLUS IONS
ZF catheter ablation of ASC-PVC guided by 3D ICE-EAM is an effective and safe procedure that reduces the radiation exposure of health care professionals and patients.

ACK N OWLED G M ENTS
The authors thank Laura Larios González of Biosense-Webster for her assistance in obtaining and processing the images used in this study.

CO N FLI C T O F I NTE R E S T
No author has conflict of interest. After introducing the sheath in the common femoral vein, the ICE catheter is carefully advanced, always maintaining the view of the venous endovascular lumen in the ICE screen. If during advancing the probe any resistance is felt or the endovascular lumen view is lost, the probe is withdrawn a few centimeters and rotated in order to look for the endovascular lumen. After the venous lumen is seen, a slight anterior tilt is performed with the probe toward that area and the catheter is moved forward in order to advance the probe without any stop or resistance in the wall vessel and avoiding the entrance in a venous branch. Catheter withdrawal and redirection were typically required and this sequence of movements was repeated until reaching the heart.

A PPE N D I X 2 .
Example of zero-fluoroscopy catheter advancement retrogradely through the aorta via femoral arterial access to approach ASC.
In the arterial access, once the catheter has been introduced through the sheath, the catheter is advanced with gentle twisting movements. If any resistance is felt, the catheter is withdrawn and slight deflections and twists are made trying again to advance the catheter until it does so without resistance, reaching the descending aorta.
At this point, the tip of the catheter is visible in the Carto System.
Then, the catheter is advanced until reaching the anatomical area corresponding to the aortic arch. In a left anterior oblique view in the Carto System, a slight deflection of the catheter is made with the tip directed toward the ascending aorta (previously reconstructed with the Carto-Sound) and is advanced gently. If no resistance is felt, the catheter is advanced until reaching the plane of the aortic valve. If any resistance is felt during the advancement of the catheter in the aortic arch, the catheter is usually pulled back and then, the anteflexion is increased and the catheter is progressed without resistance to the aortic valve plane.