ABSTRACT
Background
Radiofrequency (RF) ablation of premature ventricular complexes (PVCs) is a well‐established treatment for patients high PVCs burden, even when arising from epicardial/intramural localization. Consistent data about safety of using high power RF is lacking in the literature in these regions.
Aim
The aim of this study is to investigate the safety of different RF power settings, efficacy and outcome of non‐endocardial PVCs ablation.
Methods
Consecutive patients who underwent PVC ablation were included (2017–2023). We defined “Non‐Endocardial Radiofrequency Ablation”(NERA) a procedure in which at least one ablation site has been identified into the CVS, aortic cusps, inter‐leaflet region or pulmonary cusps.
Results
Total number of NERA sites was 64 in 56 procedures. In 63% of the procedures, high power (≥ 40 W) and in 60% long duration (≥ 60 s) RF was delivered in at least one site (median power: 40 W(30–40), median duration of single RF 54 s(45–91). In 21% of the procedures, a combination of both high power and long duration RF applications was performed. Overall procedural success was achieved in 46 procedures 82%), complete in 39 (70%), partial in 7 (12%). Only one severe complication (pericardial bleeding) was observed. Multisite ablation was associated with procedural failure. During follow‐up, median PVC burden was 0.5%(0.5–9.5), with a median reduction of 97%. Multisite ablation and coronary venous system RF were predictors of recurrence (HR 3.6; p = 0.03) and HR 3.85; p = 0.02).
Conclusion
Ablation from non‐endocardial sites is a safe and effective procedure, even using high power and/or long duration RF with clear benefit in terms of PVC burden reduction.
Keywords: aortic cusps, coronary venous system, LV summit, premature ventricular complexes, radiofrequency ablation
Non‐endocardial radiofrequency ablation of PVCs is a safe and effective procedure, even with the use of high power and/or long duration RF application. Clinicians should consider this approach in case of LV summit and/or ASV PVCs, although long‐term follow‐up is still characterized by a relatively high recurrence rate.
1. Background
Radiofrequency ablation of premature ventricular complexes (PVCs) is a well‐established treatment for patients with symptomatic, high‐burden PVCs, with or without left ventricular dysfunction [1]. The 2022 ESC guidelines of treatment of ventricular arrhythmias and prevention of sudden cardiac death provide different recommendations to this treatment: in particular, other than right ventricular outflow tract (RVOT)/left fascicular PVCs are given Class I indication only if ventricular dysfunction is present [1] or pharmacological treatment failed to achieve PVCs suppression. Although RVOT/fascicular PVCs are the most frequent PVCs encountered in clinical practice, it's not uncommon to perform radiofrequency ablation of PVCs originating from other sites, including epicardial/intramural sources of origin (SOO), like those originating from the left ventricular summit (LVs) and aortic sinuses of valsalva (ASV). In particular, the former accounts for up to 15% of the total number of left ventricular arrhythmias [2, 3], while the latter accounts up to 18%, according to different studies [4, 5]. In case of LVs PVCs, the ablation procedure can be performed with different approaches to access this area, usually retro‐aortic to access ASV, interleaflet triangle and/or subaortic area or through the cardiac venous system to access the distal coronary sinus and/or the anterior interventricular vein. Unfortunately, only small studies investigating catheter ablation of PVCs arising from these non‐endocardial SOO with details of ablation settings have been published, probably because of the low prevalence of these localizations. In addition, due to the anatomical peculiarity of these regions, some physicians are concerned about the safety of the procedure: in fact, severe and life‐threatening complications can occur, such as coronary artery injury or thrombosis, coronary venous system perforation with subsequent pericardial effusion and/or cardiac tamponade, and aortic valve damage, although the rate of this complication is low [6, 7, 8]. Due to this hypothetical risk, recommendations about power settings suggest avoiding the use of high power (> 40 W) RF [9, 10, 11]. The aim of this observational, retrospective study is to investigate the procedural safety, efficacy and outcomes of radiofrequency ablation of PVCs by ablating non‐endocardial structures via endovascular access (ASV, pulmonic cusps, interleaflet triangle and/or coronary sinus) using high power and/or long duration applications if needed.
2. Methods
2.1. Definitions and Baseline Characteristics
We defined a non‐endocardial radiofrequency ablation (NERA) as a procedure in which at least one ablation site, with subsequent radiofrequency delivery at that specific site, has been identified in the cardiac venous system (CVS), ASV, or inter‐leaflet region, above the aorto‐ventricular junction, or pulmonary cusps. We selected the study population from a series of consecutive patients who underwent radiofrequency ablation of PVCs from January 2017 to May 2023 at the Hospital Clinic of Barcelona, in whom at least one radiofrequency application was delivered according to the previous definition. The indications for the ablation procedure were the presence of symptoms, LVEF reduction, high PVC burden (> 20%) or a biventricular pacing percentage less than 95% in patients who were cardiac resynchronization therapy carriers. All patients underwent extensive clinical evaluation before the procedure, with 12‐lead standard electrocardiogram (EKG), a 24‐hour EKG Holter, a transthoracic echocardiogram and AngioCT of coronary vasculature and major intrathoracic vessels. After the initial evaluation, in patients with a history of structural heart disease or PVC‐induced cardiomyopathy, second‐level imaging technique, such as cardiac magnetic resonance and coronary angiography were performed, to further clarify the etiology of the cardiopathy. The PVCs burden was automatically calculated by the software (GE Cardio‐Day) from 24 h Holter EKG after the revision of the raw data by a specialized technician.
2.2. Mapping and Ablation Procedure
Radiofrequency ablation procedures were realized routinely with local anesthesia, with conscious or deep sedation or general anaesthesia used only if clinically indicated because of patient's characteristics. Antiarrhythmic drugs were discontinued at least five half‐lives before the day of the procedure. Electroanatomic mapping was performed with CARTO (Biosense Webster TM), Ensite Precision (Abbott TM) or EnsiteX (Abbott TM) mapping systems. When high definition activation mapping was performed, PentaRay NAV (Biosense Webster TM) or Advisor HDgrid (Abbott TM) were used as mapping catheters. Point to point mapping and radiofrequency ablation were performed using Thermocool SmartTouch (Biosense Webster TM) or Tacticath (Abbott TM) catheter. If a preprocedural CT or MRI 3D reconstruction of the heart, coronary vessels, coronary venous system, aorta, and pulmonary artery was available, segmentation was performed using specific software (ADAS3D, Galgo Medical, Barcelona). An activation map was performed if enough PVC burden, starting from the cardiac chamber in which the SOO was suspected based on EKG morphology. In case of very low PVC burden during the procedure the ablation procedure was guided by pace‐mapping. In case of suspected left‐sided localization, retrograde aortic approach was the first choice: if not feasible, transeptal puncture was performed. If the left side approach was used, systemic anticoagulation with unfractionated heparine was performed to reach the activated clotting time of > 300 s. The area of interest was determined by earliest activation time combined with the morphology of unipolar electrogram if an activation map was performed. In case of pacemapping, the area of interest was determined if there was a concordance of 95% or more. If the 3D model of the coronary vessels was not available, selective coronary angiography [12] through the ablation catheter was performed if the area of interest was anatomically close to the arterial coronary system, to assess distance of the ablation spot to left main. In the case of the suspicion of the SOO localization into the CVS, a combined approach with fluoroscopy, 3D mapping and 3D anatomical model merged from CT‐scan was used to navigate within it. Only in the case in which the 3D model of the coronary vessels was not available and the ablation was performed in the coronary venous system, coronary angiography through radial access was realized to assess safe distance from epicardial coronary arteries. Radiofrequency energy was delivered at the site of earliest activation and/or the best pace‐map score with the target temperature set at 45°C–50°C and maximum power output of 40 W. In case of unsuccessful suppression of PVCs during radiofrequency (RF) application with conventional setting (20–40 W, 60 s, 45°), high power (> 40 W) and/or long duration (> 60 s) RF applications were realized, according to operator choice, with a temperature upper limit set at 50°. If ablation at the targeted NERA site proved ineffective, a remapping of the adjacent cardiac chambers was performed to identify alternative ablation targets. This process also included the assessment of endocardial sites; however, these sites were excluded from the final analysis. The approach in the CVS was the same as the approach used in other localization but starting usually with lower power settings (20 W) to allow prolonged application to allow convective heating to reach deep tissue [13] rather than increasing power that could favour steam‐pops or charring. Multisite ablation was defined as a procedure in which radiofrequency was delivered in at least two different anatomical sites. Continuous impedance monitoring during RF delivery was evaluated to assess for sudden increase of impedance (that could be a marker of risk of steam pop) or continuous dropping of impedance without reaching a plateau phase. While applicating RF in the CVS, a relative impedance drop cut‐off of 15% during the RF application was set. If the impedance drop was higher, as well as with impedance rise, RF application was stopped. Complete procedural success was defined as the absence of PVCs at least 30 min after the effective application, in basal condition and under isoproterenol infusion. Partial procedural success was defined as the reduction of PVC burden > 80% without complete elimination [14, 15].
2.3. Follow‐Up
Follow‐up was scheduled as follows: clinical evaluation, 12‐lead standard EKG, 24‐h EKG Holter and transthoracic echocardiogram were performed at three, six and twelve months after the procedure. Regarding the study analysis, the follow‐up period was concluded upon detection of a recurrence, although it continued as per standard clinical practice. Antiarrhythmic drugs were discontinued if possible. Long‐term success was defined as a > 80% burden reduction (Δ) or < 10% absolute PVCs burden (only if the preprocedural burden was > 20%) was present during the follow‐up, as previously described [14, 16]. The local ethics committee approved the study protocol, and all patients provided written consent to be enrolled in the registry. The study was conducted according to Helsinki declaration.
2.4. Statistical Analysis
Continuous variables are presented as the median value (IQR 25%–75%). Categorical variables were expressed as total number (percentages). Chi‐squared test was used to compare acute procedural success rates between groups. The Mann–Whitney U test was used to compare the medians of the ablation parameters in the coronary venous system. The (event‐free) survival of patients was evaluated with the Kaplan–Meier method. The effect of different variables on (event‐free) survival was investigated using the Cox proportional hazards model. Variables that showed an effect on (event‐free) survival in univariate analyses with a p‐values less than 0.10 were entered in a multivariate Cox proportional hazards model using a backward stepwise selection to obtain the final model. At each step, the least significant variable was discarded from the model until all variables in the model reached a p‐value below 0.10. For all tests, a p‐value < 0.05 was considered significant. Statistical analysis was performed using R software for Windows version 4.2.2 (R project for statistical computing; Vienna, Austria).
3. Results
3.1. Baseline Characteristics
During the study period (2017–2023), 429 patients underwent PVC radiofrequency catheter ablation. Of those patients, 53 fulfilled the inclusion criteria and were included in the study. The total number of procedures in which a NERA site was identified was 56, due to the need to perform a REDO procedure in 3 patients (Figure 1). Overall, 36 (69%) patients were male; median age was 60 (51–69). 34 (64%) patients had no underlying structural heart disease, ruled out by second‐level imaging techniques, such as CMR and coronary angiography. Median left ventricular ejection fraction (LVEF) was 44% (37.5–55), while 23 (46%) of the patients presented LVEF < 50%; 7 (14%) patients were ICD/CRTd carriers and 2 (4%) underwent ICD implantation after the ablation procedure. Of the total number of patients, 6 (11%) previously underwent a single failed attempt of catheter ablation and 3 (6%) two or more. Regarding medical treatment, 35 (74%) patients were on beta‐blocker therapy up titrated to the maximum tolerated dose, 2 (4%) patients were on Class I antiarrhythmic drugs, 6(13%) patients were on amiodarone therapy at the dose of 200 mg daily and 1 (2%) patient was on sotalol therapy. The patient baseline characteristics of the study population are summarized in Table 1.
Figure 1.
Flowchart summarizing the study population and procedural findings. (A) PVCs radiofrequency ablation from great cardiac vein. (B) Ablation of LCC PVCs: FAM merged with CT‐derived 3D model of coronary arteries. (C) bipolar ablation of PVCs arising from LV summit, EAM. (D) bipolar ablation of PVCs arising from LV summit, EAM: LAO 30° X‐Ray image.
Table 1.
Baseline study population characteristics (n = 53).
| Mean age (years) ± SD, range | 60 ± 12 (19–76) |
|---|---|
| Male, n (%) | 36 (69%) |
| Arterial Hypertension n (%) | 25 (51%) |
| Diabetes mellitus, n (%) | 12 (24%) |
| Dyslipemia, n (%) | 14 (27%) |
| LV ejection fraction (%) ± SD | 46 ± 12 (20–65) |
| ICD carriers, n (%) | 7 (14%) |
| 1st procedure, n (%) | 44 (83%) |
| 2nd procedure, n (%) | 6 (11%) |
| 3rd procedure or more, n (%) | 3 (6%) |
| Without structural heart disease, n (%) | 34 (64%) |
| Idiopathic nonischemic dilated cardiomyopathy, n (%) | 8 (15%) |
| Ischemic cardiopathy, n (%) | 6 (11%) |
| Hypertrophic cardiomyopathy, n (%) | 1 (2%) |
| Others, n (%) | 4 (8%) |
| Beta‐blockers, n (%) | 35 (74%) |
| Class I antiarrhythmic, n (%) | 2 (4%) |
| Sotalol, n (%) | 1 (2%) |
| Amiodarone, n (%) | 6 (13%) |
3.2. PVC EKG Features
The mean PVC burden was 25 ± 10%, 39 (74%) patients presented PVCs with a left bundle branch block pattern in lead V1 and 52 (98%) with inferior axis. Regarding precordial transition, 13 (24%) patients presented positive precordial concordance, 16 (30%) presented precordial transition in V2, 20 (38%) in V3 and 4 (7%) in V4 or V5‐V6. Of note, 41 (79%) of the patients presented PVCs with maximum deflection index (MDI) > 0.55, suggesting non‐endocardial (probably intramural/epicardial) origin [17]. 6 (11%) patients had more than one PVC morphology, although only the morphology identified in NERA sites was included in the analysis.
3.3. Radiofrequency Ablation Procedure
The total number of NERA ablation sites was 64: 17 (27%) in the coronary venous system (Figure 2A), 9 (14%) in the right coronary cusp, 15(23%) in the left coronary cusp (Figure 2B), 20 (31%) in the interleaflet triangle between right and left coronary cusp, reached from above the aortic cusps, and 3 (5%) from the left pulmonary cusp, reached with reverse U curve technique [18, 19, 20] (Figure 1). In 22 (39%) of the total number of procedures (n = 56) a multisite ablation was performed. In one patient, due to the suspicion of a very deep intramural ectopic focus, successful bipolar ablation was performed from great cardiac vein and sub‐valvular left ventricular outflow tract (Figure 2C,D). Median total RF time was 4.5 (2.5–10) minutes. Median total fluoroscopy time was 14 (8–23) minutes. 34 (67%) procedures were realized with CARTO 3D mapping system, 7 (12%) patients with Ensite Precision and 15 (27%) with EnsiteX. In 25 (45%) procedures a high‐definition mapping was performed (PentarayNAV in 6 and Advisor HDgrid in 19 patients). A NERA site was the first area mapped in 36 (64%) procedures. In the same line, after mapping all chambers, a NERA site was considered as the first ablation site in 44 (79%) of the procedures. Regarding radiofrequency application characteristics in 60% of the procedures, long‐duration (≥ 60 s) application was delivered in at least one of the ablation spots and high power (≥ 40 W) was used in 63% of procedures. Overall, median power was 40 W (30‐40), and median duration of single radiofrequency application was 54 s (45–91), with the longest RF application of 301 s. Noteworthy; In 21% of the procedures, a combination of both high power (≥ 40 W) and long duration (≥ 60 s) application was performed. When examining ablation in the CVS ablation, median power during RF application was significatively lower compared to other sites ablation: 30 W (20–40) vs 40 W (30–40), p = 0.01; nevertheless, the median duration of a single RF application was significatively longer than in other sites: 74 s (51–180) vs 54 s (45–103), p = 0.05. Complete acute procedural success was achieved in 39 procedures (70%), while partial procedural success was achieved in 7 procedures (12%). Only multisite ablation was significantly associated with complete failure of the ablation procedure or partial success: in 2 (6%) procedures in the single site ablation group we failed to achieve complete procedural success compared to 7 (33%) procedures in the multisite ablation group (p < 0.001); in 1 (3%) procedure in the single site ablation we only achieved a partial success, compared to 6 (29%) in the multisite ablation group. Regarding complications, in only one case complication occurred in relation with ablation site: only 1 patient (2%) developed pericardial bleeding. Overall, vascular access‐related problems (arterial pseudo‐aneurysm) were the most common complications (3 patients, 5%) without the need of surgical or endovascular repair. In the rest of the procedures (52, 93%) no complications at all occurred. The ablation sites and the application characteristics are summarized in Table 2.
Figure 2.
(A) PVCs radiofrequency ablation from great cardiac vein. (B) Ablation of LCC PVCs: FAM merged with CT‐derived 3D model of coronary arteries. (C) bipolar ablation of PVCs arising from LV summit, EAM. (D) bipolar ablation of PVCs arising from LV summit, EAM: LAO 30° X‐Ray image.
Table 2.
Radiofrequency ablation characteristics.
| Ablation site charachteristics (n = 64) | |
|---|---|
| Coronary venous system, n (%) | 17 (27%) |
| Right aortic cusp, n (%) | 9 (14%) |
| Left aortic cusp, n (%) | 15 (23%) |
| l‐RCC interleaflet triangle, n (%) | 20 (31%) |
| Left pulmonary cusp, n (%) | 3 (5%) |
| Median power (W) (IQR 25%–75%) | 40 (30–40), |
| Median temperature (°c) (IQR 25%–75%) | 40 (33–45) |
| Median time (sec) (IQR 25%–75%) | 54 (45–91), |
| Procedural safety & efficacy (n = 56) | |
| Complete procedural success, n (%) | 40 (71%) |
| Partial procedural success, n (%) | 7 (13%) |
| Procedural failure, n (%) | 9 (16%) |
| Complications, n (%) | |
| Pericardial bleeding | 1 (2%) |
| vascular complications | 3 (5%) |
3.4. Follow‐Up
Median follow‐up was 6.5 (3 – 12) months. Five patients were lost during the follow‐up. During the follow‐up period, median PVC burden was 0.5% (0.5–9.5), with a median of burden reduction of 97% (Figure 3). Kaplan–Meier analysis showed an event‐free survival of 70% (Figure 4A). From those patients who experienced recurrence, two patients underwent a successful REDO procedure during follow‐up, while in 1 the procedure had to be suspended due to a procedural complication (pericardial bleeding with cardiac tamponade). In the remaining cohort of patients, symptoms were controlled by medical therapy alone. After univariate Cox proportional hazard analysis, multisite ablation (HR 3.6; 95% CI: 1.08–12.01; p = 0.03) and ablation through coronary venous system (HR 3.85; 95% CI: 1.21–12.20; p = 0.02) were associated with recurrence (Figure 4B,C, respectively). In this context, eight patients (40%) who underwent multisite ablation experienced a recurrence compared to 4 (14%) of the patients who underwent single site ablation (p = 0.04) and seven patients (50%) who underwent ablation through coronary venous system experienced a recurrence, compared to 5 (16%) of the patients who underwent other than coronary venous system RF (p = 0.03). After multivariate Cox proportional hazard analysis, coronary venous system ablation was associated with recurrences during follow‐up (3.85 (1.21–12.2, p = 0.02). Table 3 provides a comprehensive summary of the univariate and multivariate analysis. Median LVEF at follow‐up was 55% (55–60), with a median LVEF positive change during follow‐up of 12% (0–24). Of the patients with LVEF < 50% who achieved long‐term success, 67% of them presented a normalization of LVEF.
Figure 3.
Spaghetti plot of PVC's burden before and after the ablation.
Figure 4.
(A) Kaplan–Meier analysis of event‐free survival during follow‐up. (B) Univariate Cox proportional hazard model of multisite ablation. (C) Univariate Cox proportional hazard model of coronary venous system ablation.
Table 3.
Univariate and multivariate analysis results.
| Univariate analysis | Multivariate analysis | p value | ||
|---|---|---|---|---|
| Variable | HR (95% CI) | p value | ||
| Age | 0.99 (0.94–1.03) | 0.68 | ||
| Sex | 0.71 (0.19–2.62) | 0.60 | ||
| Cardiopathy | 1.57 (0.51–4.86) | 0.44 | ||
| Procedure number | 2.61 (0.71–9.65) | 0.15 | ||
| Precordial Transition | ||||
| ## Precordial concordance | 0.93 (0.25–3.43) | 0.91 | ||
| ## V2 | 1.12 (0.25–4.99) | 0.89 | ||
| ## V3 | 0.83 (0.19–3.73) | 0.81 | ||
| ## V4 or later | 1.02 (0.11–9.87) | 0.99 | ||
| PVC Axis (superior vs inferior) | 4.54 (0.57–35.96) | 0.15 | ||
| MDI > 0.55: | 0.71 (0.19–2.63) | 0.61 | ||
| PVC burden | 1.00 (0.94–1.07) | 0.88 | ||
| Right coronary cusp | 0.98 (0.21–4.47) | 0.98 | ||
| Left coronary cusp | 0.46 (0.1–2.08) | 0.31 | ||
| Interleaflet triangle | 1.8 (0.34–3.4) | 0.90 | ||
| Multisite ablation | 3.6 (1.08–12.01) | 0.03 | ||
| Coronary venous system ablation | 3.85 (1.21–12.2) | 0.02 | 3.85 (1.21–12.2) | 0.02 |
Note: The bold and italic values are indicate statistically significance.
3.5. Redo Procedures
In three of the patients of the full cohort, a redo procedure was attempted.
Patient 1: Previously underwent RF ablation in the left coronary cusp but experienced early recurrence. Mapping of both the left ventricular outflow tract (LVOT) and the great cardiac vein revealed equal precocity (−10 ms, both in bipolar and unipolar electrograms). Unipolar RF ablation was unsuccessful on both sides, leading to a decision for bipolar ablation. Using two irrigated catheters (TactiCath 4 mm in the great cardiac vein as the RF source and FlexAbility 4 mm in the LVOT as the return electrode), PVCs were successfully abolished after the first application (20 W, 25°C, 180 s).
Patient 2: Previously underwent ablation at the interleaflet triangle with complete procedural success using standard RF parameters. However, at the 3‐month follow‐up, PVCs recurred with the same morphology and burden. Electroanatomic mapping showed similar precocity at nearly the same anatomical location. High‐power, long‐duration RF applications were performed, leading to partial success. During follow‐up, the patient remained asymptomatic, with a PVC burden < 10%.
Patient 3: Previously underwent ablation in the middle cardiac vein but experienced early recurrence. PVC morphology (LBBB pattern in V1, superior axis, and V2 precordial transition) suggested a source of origin in the middle cardiac vein, consistent with the initial procedure. Activation mapping confirmed identical precocity at the prior ablation site. High‐power RF applications were attempted, but after a few unsuccessful applications, sudden hypotension occurred. Bedside echocardiography revealed pericardial effusion. Emergent pericardiocentesis was performed successfully, and the patient was stabilized, requiring ICU admission but no surgical intervention.
4. Discussion
The present study describes the safety, efficacy, and outcome after 12 months follow‐up of NERA of PVCs, using high‐power and/or long‐duration radiofrequency lesions in a significant proportion of patients, with an acute success rate of 84% and an event‐free survival at 12 months longitudinal follow up of 70% with a single procedure. These results expand upon previous reports by systematically evaluating the safety and efficacy of intensive ablation parameters in challenging anatomical locations.
Due to the intrinsic nature of non‐endocardial ectopic foci, sometimes high power and long duration radiofrequency delivery are needed to achieve PVC suppression. In our series, a significant proportion of procedures required high power (≥ 40 W, up to 50 W in 63% of patients and/or long RF applications, ≥ 60 s, up to 304 s, 60% of patients). Moreover, in 21% of the procedures, a combination of both high power (≥ 40 W) and long duration (≥ 60 s) application was needed to achieve PVCs suppression. To our knowledge, this is the first study that assesses specifically in a consecutive series of patients the safety and efficacy of both high power and long duration applications in non‐endocardial locations.
4.1. Safety Profile
Prior studies described approaches in which, both in ASV and in the coronary venous system, ablation power was typically limited to 30 W in CVS and 30‐40 W in ASV [20, 21]. In both locations there is the potential specific risk of cardiac perforation (CVS) and damaging coronary arteries (CVS and ASV) and aortic leaflets (ASV) [22]. Our findings challenge this conservative paradigm, showing that higher power settings (up to 50 W) and prolonged applications (up to 304 s) can be employed safely when guided by contemporary monitoring techniques. The absence of steam pops or coronary complications in our series, despite 63% of cases using ≥ 40 W and 60% employing ≥ 60 s applications, supports this approach. This safety profile likely reflects our rigorous monitoring protocol, including real‐time impedance tracking (with particular attention to avoiding sudden drops > 15–20 Ω) [19, 20, 21], preprocedural CT integration for anatomical assessment [12, 16], and the systematic use of contact‐force sensing catheters [21, 22, 23, 24]. In terms of coronary arteries iatrogenic injury, a previous study from our group described the safety of using selective angiography through the ablation catheter in the ablation spot to assess the distance to coronary ostia [12]. In addition, also published by other groups [20], we usually merge a preprocedural CT scan to also confirm the distance from our catheter to coronary ostia and to help the navigation through the coronary venous system. Regarding the use of impedance monitoring safety of high power and/or long duration and possible steam pops and/or perforation, several studies have related the impedance drop with lesion depth. In this sense, impedance drop more than 15/20 Ohms [23], sudden drops or, on the contrary, small rises [21] have been found to be predictors of char formation in animal studies [25]. An illustrative example of the relevance of impedance monitoring when dealing with bail‐out strategies is its use in case of half normal saline ablation [23, 26]. In our daily practice, continuous monitoring of impedance during RF ablation plays a key role in avoiding steam pops, even with high power and/or long duration ablation. In fact, in our series no steam pops occurred, even in the patient who experienced a cardiac tamponade. Moreover, the use of contact force catheters (Tacticath, Abbott TM and Thermocool SmartTouch, Biosense‐Webster) allowed us to continuously monitor the force applied to the tissue during ablation. Although some studies [24, 27] have not demonstrated a significant difference in the outcomes of outflow tract PVC ablation between contact force and traditional catheters, the use of a contact force catheter has nonetheless been helpful in determining the appropriate power and/or duration of the RF applications. Overall, these safety measures, the coronary damage risk and all other lesion formation risks seem very low and, in our series, despite using high power and/or longer applications, no coronary injury at all was observed. This could be very relevant as in these locations it is very frequent to deal with deep foci so this kind of ablation settings could be necessary [28] Other bailout techniques consist of RF ablation with half normal saline irrigation [29] and needle ablation [30], although these techniques were not used in our study. Very few studies have compared all of these techniques with the exception of an animal study that showed that bipolar ablation is similar in terms of lesion depth than sequential unipolar ablation using half normal saline [31]. Data available in the literature about the usefulness of bipolar ablation in clinical practice are mostly derived from case series or small‐sized studies [32, 33, 34], with good results. Moreover, a recent multicenter study by Futyma et al. [35] evaluated the safety and efficacy of bipolar ablation in a large cohort of patients with refractory ventricular tachycardia, showing a better success rate (not randomized) with bipolar ablation with also a good safety profile.
4.2. Success and Recurrences
Regarding acute success and recurrences, our results are in line with studies already present in the literature. Interestingly, our results are similar to those of Chung et al. [36], especially in terms of procedural success and recurrence predictors, although with a smaller sample size and shorter follow‐up. As in that study, we found that multisite ablation is strongly associated with procedural failure (both complete failure or achieving partial procedural success) and recurrence during the follow‐up. A possible explanation is that the need for multisite ablation reflects the presence of a very deep ectopic focus, in which the resistive and conductive heating of the myocardium is often difficult to achieve, due to the dispersion of radiofrequency energy [37]. Additionally, we found that CVS ablation is also a strong predictor of recurrence, both in univariate and multivariate analyses. This may be due to different reasons. Firstly, the inherent high impedance of CVS limits the radiofrequency delivery. In this sense, the risk of high impedance rises and subsequent steam pop, if using high power settings, could lead to life‐threatening complication, such as hemopericardium and/or cardiac tamponade [9]. This risk could limit the amount of radiofrequency that can be delivered. Finally, the fat surrounding the coronary sinus could also limit the transmission of radiofrequency. Other parameters, such as EKG morphology of PVCs or PVCs burden failed to show a statistically significant association with procedural failure of recurrence. Regarding clinical usefulness of ablation, our results are in line with other studies in literature [38, 39], as we observed a relevant improvement of LVEF (mean LVEF improvement of 14 ± 25%), with 67% of the patients, who presented with impaired LVEF and were free from PVCs recurrence during follow up, experienced a normalization of LVEF, as previously described by Lee et al. [40].
4.3. Study Limitations
This observational study presents some limitations. Firstly, although both the inclusion and the follow‐up of the patients were prospective, the analysis of ablation settings was retrospective. Another limitation is that we included both patients with and without cardiac disease, leading to a very heterogeneous population. However, since the main objective of the study was to prove the safety of high power and/or long duration applications, we consider that this limitation does not significantly impact our results. Furthermore, a systematic follow‐up with coronary angiography and/or functional ischemia testing was not scheduled, although none of the patients presented ischemic symptoms or acute coronary syndromes during follow‐up. Finally, it must be considered that our centre is a tertiary care electrophysiology centre with high level expertise and high volume of procedures performed per year. It is important to note that these findings may not be applicable to less experienced operators or centres. In this sense, the merge of preprocedural imaging to avoid coronary damage is not available in some hospitals and could have influenced the high safety profile of our series.
5. Conclusions
The results of this study suggest that NERA of premature ventricular complexes in the ASV and CVS is a safe and effective procedure. High‐power and long‐duration of radiofrequency delivery are often required to achieve good procedural success although recurrence rate during follow‐up remains high. Multisite ablation is associated with procedural failure or partial success, as well as an increased risk of PVC recurrence, while an origin near the coronary venous system strongly predicts PVC recurrence.
Disclosures
L.M. reports activities as consultants, lecturers, and advisory board members for Abbott Medical, Boston Scientific, Biosense Webster, Medtronic, and Biotronik. He is also a shareholder of Adas3D Medical, S.L. I.R.L., J.M.T. and A.P.S. report activities as consultants and lecturers for Biosense Webster, Medtronic, Boston Scientific and Abbott Medical. J.B.G. reports honoraria as a consultant from Microport CRM, a lecturer from Microport CRM and Abbott, and unrestricted grant support for a fellowship from Abbott Labs. All other authors report that they have no relationships relevant to the contents of this paper to disclose.
Acknowledgments
This study was supported by Instituto de Salud Carlos III (ISCIII) PI20/00693/CB16/11/00354, co‐founded by European Union, Grant 2021_SGR_01350, SGR21/GENCAT, Catalonia, Spain.
Data Availability Statement
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.