| TYPE Original Research PUBLISHED 06 June 2023 DOI 10.3389/fcvm.2023.1162197 Reassessment of the electrical connection between the EDITED BY Robert Hatala, National Institute of Cardiovascular Diseases, pulmonary veins and the left Slovakia REVIEWED BY atrium: A study to determine the Robert Cihak, IKEM, Czechia different contributions of myocardial fibers along the Stepan Havranek, Charles University, Czechia *CORRESPONDENCE Bieito Campos-García bcamposg@santpau.cat standard ablation circumference RECEIVED 09 February 2023 ACCEPTED 18 May 2023 Bieito Campos-García*, Concepción Alonso-Martín, PUBLISHED 06 June 2023 José M. Guerra, Zoraida Moreno-Weidmann, Francisco Méndez- CITATION Zurita, Rodolfo Montiel-Quintero, Campos-García B, Alonso-Martín C, Guerra JM, Moreno-Weidmann Z, Méndez-Zurita F, Andrés Betancur-Gutiérrez, Xavier Viñolas-Prat Montiel-Quintero R, Betancur-Gutiérrez A, and Enrique Rodríguez-Font Viñolas-Prat X and Rodríguez-Font E (2023) Reassessment of the electrical connection Arrhythmia Unit, Department of Cardiology, Hospital de la Santa Creu I Sant Pau, CIBERCV, Institut de between the pulmonary veins and the left Recerca HSCSP-IIB Sant Pau, Universitat Autònoma de Barcelona, Barcelona, Spain atrium: A study to determine the different contributions of myocardial fibers along the Background: Circumferential ablation around the ipsilateral pulmonary veins (PVs) standard ablation circumference. Front. Cardiovasc. Med. 10:1162197. is the standard strategy for atrial fibrillation ablation. The present study seeks to doi: 10.3389/fcvm.2023.1162197 assess which regions of the standard ablation circumference are the main COPYRIGHT contributors to the venoatrial electrical connection. © 2023 Campos García, Alonso-Martín, Guerra, Methods: A total of 41 patients were included under a specific atrial fibrillation Moreno-Weidmann, Méndez-Zurita, Montiel- ablation protocol in which the anterior and posterior segments of the standard Quintero, Betancur-Gutiérrez, Viñolas-Prat and Rodríguez-Font. This is an open-access article circumference, between the equatorial line of the superior and the inferior distributed under the terms of the Creative ipsilateral PVs, were ablated first. If PV isolation was not achieved, ablation was Commons Attribution License (CC BY). The use, extended superiorly or inferiorly, on the basis of the earliest atrial activation distribution or reproduction in other forums is permitted, provided the original author(s) and recorded during pacing from inside the PV. Complete PV isolation and the the copyright owner(s) are credited and that the length of the areas not requiring ablation (ANRA) at the time of electrical original publication in this journal is cited, in isolation were evaluated. accordance with accepted academic practice. No use, distribution or reproduction is Results: Ablation of the anterior and posterior segments of the standard permitted which does not comply with these circumference led to the isolation of 77% left-PV pairs and 51% right-PV pairs terms. ( p = 0,015). A superior extension was required in 23% left-PV pairs and in 46% right-PV pairs, while an inferior extension was required only in 10% left-PV pairs and in 11% right-PV pairs. PV isolation was achieved before completing the standard ablation circumference in 97% left-PV pairs and in 94% right-PV pairs, with a median ANRA of 36.9 (IQR: 30.9–42.1) mm in the left PVs [16.0 (IQR: 12.0–19.0) mm superior and 18.8 (IQR: 16.1–24.9) mm inferior, p < 0.01] and 36.9 (IQR: 30.2–41.0) mm in the right PVs [15.1 (IQR: 10.7–19.1) mm superior and 20.6 (IQR: 16.9–23.3) mm inferior, p < 0.01]. Conclusions: The myocardial fibers along the anterior and posterior regions of the standard ablation circumference are the main contributors to the electrical connection between the pulmonary veins and the left atrium. Ablation of these regions results in PV isolation in the majority of patients. KEYWORDS atrial fibrillation, ablation, pulmonary vein, electrical connection, myocardial fiber Frontiers in Cardiovascular Medicine 01 frontiersin.org Campos-García et al. 10.3389/fcvm.2023.1162197 Introduction All procedures were performed under the condition of general anesthesia. Standard multielectrode catheters were advanced Circumferential ablation around the ipsilateral pulmonary inside the coronary sinus and in the His bundle region. A veins (PVs) has been adopted as the standard strategy for PV single atrial transseptal puncture was performed using the isolation (1). However, the arrangement of muscle fibers along standard Brockenbrough technique, and a cool-tip ablation the junction between the PVs and the left atrium (LA) is catheter and a multielectrode mapping catheter were introduced complex and heterogeneous. This heterogeneity could result in in the LA. Intracardiac electrograms were recorded using the different contributions of these fibers to the PV–LA electrical Prucka CardioLab electrophysiology system (GE Medical connection along the standard ablation circumference (2–4). Systems, Milwaukee, WI, USA). All patients were in the state of Previous anatomical and electrophysiological studies have shown sinus rhythm during mapping, ablation, and evaluation of PV that the myocardial fibers located in the carina between the isolation. Electrical cardioversion was performed whenever ipsilateral PVs are thicker, markedly intermingled, and critical in necessary to revert any episode of atrial fibrillation during the maintaining the electrical connection between the LA and the procedure. PVs (Figure 1) (5–8). High-density electroanatomic maps were created during atrial The present study sought to assess which regions of the pacing from the distal coronary sinus using the CARTO 3 system standard ablation circumference are the main contributors to the (Carto System®, Biosense-Webster Inc., Diamond Bar, CA, USA) PV–LA electrical connection. Since ablation of the anterior and with the PentaRay® 20-pole steerable mapping catheter posterior regions of the standard ablation circumference targets (Biosense-Webster, Inc., Diamond Bar, CA, USA). The resulting the myocardial fibers entering the carina region, we hypothesized electroanatomical maps were merged with the left atrium images that ablation of these segments could result in the isolation of the previously obtained by MRI or CT scan using the CartoMerge ipsilateral PVs before the completion of the circumferential tool (CartoMerge®, Biosense-Webster, Inc.). Patients with ablation process. significant areas of bipolar low voltage shown on the high- density map of the left atrium, consistent with scarring (≥1 cm2, <0.5 mV), were not included in the study. Ablation was performed using the irrigated tip contact force– Materials and methods sensing RF ablation catheter Thermocool SmartTouch® (Biosense-Webster Inc., Diamond Bar, CA, USA) with a power Study population of 30 W and a maximum temperature of 43° at a flow rate of 20 ml/min. The target ablation index was 420 in the anterior wall A total of 41 consecutive patients undergoing a first procedure and 370 in the posterior wall with an interlesion distance ≤5 mm. of radiofrequency (RF) catheter ablation for PV isolation were included. All procedures were performed following the guidelines of the Institutional Committee on Human Research at Hospital Ablation protocol Sant Pau, and all patients provided written informed consent. We designed an ablation protocol in which the anterior and posterior segments of the standard circumference around the ipsilateral veins were ablated first (Figure 2). The length of these segments was empirically defined from the equatorial level of the superior PV to the equatorial level of the inferior PV (Figures 3, 4). Ablation was initiated on the left side PVs with the PentaRay catheter placed in the superior PV. Radiofrequency applications were delivered along the anterior segment in a downward direction, and along the posterior segment, in an upward direction. Once ablation at both the anterior and the posterior segments was performed, PV electrical connection was evaluated with the PentaRay catheter. Pacing from inside the PVs was FIGURE 1 systematically performed by using the PentaRay catheter to assess Arrangement of myocardial fibers along the venoatrial junction in the left atrium. (A) Dissection showing a posterior view of the left atrium the exit block and confirm PV isolation. In the event that both with transillumination to demonstrate the thinner sections. (B) A ipsilateral PVs were isolated, a new high-density voltage map of histological section in the transverse plane of a left-PV pair stained with Masson’s trichrome technique to show variations in the widths of the PV pair and the adjacent LA was acquired to further confirm muscular fibers along the venoatrial junction. Note that myocardial complete PV isolation and to assess the extent of voltage changes fibers entering the carina are thicker (red arrows), while they are relative to the baseline voltage map (Figure 3). thinner and exhibit discontinuities in the superior and inferior aspects of the PV pairs (green arrows), especially on the left side. LSPV, left In the case that any of the ipsilateral PVs remained connected, superior pulmonary vein; LIPV, left inferior pulmonary vein; PVs, atrial activation adjacent to the ablated segments was mapped using pulmonary veins; SVC, superior vena cava; IVC, inferior vena cava. the ablation catheter, during pacing from inside the PV with the Histological images provided courtesy of Dr. José Angel Cabrera. PentaRay® catheter. Based on the earliest atrial activation, one of Frontiers in Cardiovascular Medicine 02 frontiersin.org Campos-García et al. 10.3389/fcvm.2023.1162197 Results Patient characteristics The baseline characteristics of the 41 patients in the study are listed in Table 1. A total of 29 (71%) patients had paroxysmal AF, and 12 (29%) had persistent AF. Four patients (10%) had known structural heart disease: two with ischemic heart disease with preserved left ventricular systolic function and two with non- ischemic disease with mild and moderately reduced left ventricular ejection fraction due to tachycardiomyopathy, and these conditions normalized after good rhythm control was achieved in both patients. On preprocedural imaging assessment, 20 patients (49%) were found to have a left common ostium, one patient (2%) had a right common ostium, and seven (17%) had an additional right PV. Vein potentials were recorded in all PVs prior to ablation. First-pass PV isolation was observed in 39 (95%) left-PV pairs and in 35 (85%) right-PV pairs, which were available for analysis. Procedural data are presented in Tables 2 and 3. Pulmonary vein isolation during ablation to the anterior and posterior segments of the standard circumference FIGURE 2 Flowchart of the study ablation protocol. Ablation of the anterior and posterior segments of the standard circumference resulted in complete electrical isolation of both ipsilateral veins in 30 (77%) left-PV pairs and in 18 (51%) right- the ablated segments was extended either upward, around the PV pairs (p = 0.015) (Figures 3, 4). superior PV, or downward, around the inferior PV, until PV In the left PVs, ablation of the anterior segment required a electrical isolation was achieved (Figures 2, 5). median of 9 (IQR: 7–10) RF lesions, while the posterior segment The rate of complete PV isolation before closing the standard required 7 (IQR: 6–8) RF lesions. The number of RF lesions ablation circumference and the length of the areas not requiring required to achieve PV isolation was significantly lower than the ablation (ANRA) at the time of PV isolation were evaluated total lesions needed to complete the ablation of the (Figures 4, 6). circumference in these PV pairs, 17 (IQR: 12–19) vs. 26 (IQR: Regardless of whether PV isolation was achieved at the end of 21–28) (p < 0.01). The median length of the ANRA at the time the ablation protocol, completion of the circumferential standard of complete PV isolation was 17.2 (IQR: 14.1–20.5) mm in the ablation process was always achieved around the ipsilateral PVs. superior aspect of the circumference and 20.4 (IQR: 16.4– First-pass ablation was considered when PV isolation was 24.3) mm in the inferior aspect of the left circumference. obtained during the implementation of the ablation protocol or In the right PVs, ablation of the anterior segment required a at the completion of the circumferential line. PV groups without median of 9 (IQR: 8–10) RF lesions, while ablation of the posterior first-pass isolation were excluded from the analysis. segment required 8 (IQR: 7–10) RF lesions. The number of RF lesions required to achieve PV isolation was also lower than the total lesions needed to complete the ablation of the circumference in Statistical analysis these PV pairs, 17 (IQR: 15–20) vs. 27 (IQR: 24–29) (p < 0.01). The median length of the ANRA at the time of complete PV isolation Continuous data are expressed as mean ± standard deviation or was 18.5 (IQR: 15.2–22.8) mm in the superior aspect and 21.4 (IQR: median (interquartile range) when appropriate. Categorical 18.5–24.8) mm in the inferior aspect of the right circumference. variables are expressed in percentages. All continuous data were tested using the one-sample Kolmogorov–Smirnov test against a normal distribution. A comparison between groups was made Extended ablation from the initial anterior using the Student’s t-test, the Mann–Whitney U-test, and the X 2 and posterior segments test, according to the type of variable and its distribution. A p- value <0.05 was considered statistically significant. The analysis Nine left-PV pairs (23%; 9 left-superior and 8 left-inferior PVs) was conducted by using the IBM SPSS Statistics version 26.0 and 17 right-PV pairs (49%; 16 right-superior and 12 right-inferior (SPSS, Chicago, IL, USA). PVs) remained connected after ablation of the anterior and Frontiers in Cardiovascular Medicine 03 frontiersin.org Campos-García et al. 10.3389/fcvm.2023.1162197 FIGURE 3 Complete isolation of left and right-PV pairs after ablation of the anterior and posterior segments of the standard circumference around the ipsilateral PVs. Posterior and anterior views of the LA electroanatomical maps are shown. (A) High-density voltage map of the LA obtained before ablation. (B) The electroanatomical map is shown in gray with the RF lesions (ablation tags), delivered only in the anterior and posterior segments of the standard circumference around the ipsilateral PVs (yellow line), resulting in complete electrical isolation. (C) High-density voltage map acquired after PV isolation. Note that the low-voltage areas, consistent with electrical isolation, extend all around the ipsilateral PVs, including the upper and lower aspects of the PV pair, where ablation was not performed (ANRA). posterior segments. In these cases, the initially ablated segments anteriorly and four posteriorly. The superior ablation extensions were extended on the basis of the earliest atrial activation achieved the isolation of eight left-superior PVs and of four left- identified during pacing from inside the connected PV (Figure 5). inferior PVs after a median of three (IQR: 2–4) additional RF lesions. The left-superior PV that remained connected was Left pulmonary veins successfully isolated during the subsequent inferior ablation extension. A superior extension from the initially ablated segments was An inferior extension from the initially ablated segments was required in all nine left-PV pairs that remained connected, five required in four of the nine left-PV pairs that remained Frontiers in Cardiovascular Medicine 04 frontiersin.org Campos-García et al. 10.3389/fcvm.2023.1162197 FIGURE 4 Schematic representation illustrating the observations after ablation to the anterior and posterior segments of the standard circumference around the ipsilateral PVs. Ablation in these segments (orange dots) resulted in complete PV isolation of 77% left-PV pairs and 51% right-PV pairs. Horizontal dashed lines have been drawn to mark the equatorial level of the PVs. The green double-headed arrows show the extent of the areas non-requiring ablation at the time of PV isolation. ANRA, areas not requiring ablation; PVs, pulmonary veins; PVI, pulmonary vein isolation. ANRA length is expressed as median (IQR). FIGURE 5 Example of ablation extension from the anterior and posterior segments guided by pacing from inside the connected PVs. A right lateral view of the right PVs that remained connected after ablation to the anterior and posterior segments of the standard circumference. The pacing was performed from the multipolar catheter inside the right-superior PV. Atrial activation next to the ablated segments was mapped using the ablation catheter. Note the earliest atrial activation identified at the superior end of the anterior ablated segment (thick yellow arrow), where two additional RF lesions led to complete PV isolation of both the superior and the inferior right PVs. Frontiers in Cardiovascular Medicine 05 frontiersin.org Campos-García et al. 10.3389/fcvm.2023.1162197 FIGURE 6 Schematic representation illustrating the observations at the end of the ablation protocol. As in Figure 4, horizontal dashed lines have been drawn to mark the equatorial level of the PVs, and the orange dots represent the initial set of RF lesions to the anterior and posterior segments of the standard circumference around the ipsilateral PVs. The blue and purple dots represent additional RF lesions in those patients requiring ablation extension from the anterior and posterior segments. The green double-headed arrows show the extent of the areas not requiring ablation at the time of PV isolation. ANRA, areas not requiring ablation; PVs, pulmonary veins; PVI, pulmonary vein isolation; SE, superior extension; IE, inferior extension. ANRA length is expressed as median (IQR). connected, two anteriorly and two posteriorly. These inferior needed to complete the ablation of the circumference in these PV ablation extensions achieved the isolation of four left-inferior pairs, 18 (IQR: 15–25) vs. 25 (IQR: 24–29) (p = 0.028). PVs and one left-superior PV after a median of four (IQR: 3–4) additional RF lesions. Right pulmonary veins The number of RF lesions required to achieve PV isolation after A superior extension from the initially ablated segments was ablation extension was still significantly lower than the total lesions required in 16 of the 17 right-PV pairs that remained connected, 14 anteriorly and two posteriorly. The superior ablation extensions achieved the isolation of 15 right-superior PVs and of TABLE 1 Baseline characteristics of the patients included in the study. eight right-inferior PVs after a median of two (IQR: 2–3) N 41 additional RF lesions. The right-superior PV that remained Age (years) 59 (53–64) Male (%) 30 (73) connected was successfully isolated during the subsequent Hypertension (%) 15 (37) inferior ablation extension. Diabetes mellitus (%) 3 (1) An inferior extension from the initially ablated segments was Structural heart disease (%) 4 (10) required in four of the 17 right-PV pairs that remained LVEF 0.60 (0.56–0.60) connected, two anteriorly and two posteriorly. These inferior Left atrium diameter (mm) 42 (39–46) ablation extensions achieved the isolation of four right-inferior Type of atrial fibrillation (%) PVs and one right-superior PV after a median of two (IQR: 1–2) Paroxysmal 29 (71) Persistent 12 (29) additional RF lesions. Antiarrhythmic drugs (%) 36 (88) The number of RF lesions required to achieve PV isolation after Flecainide 18 (44) ablation extension was also significantly lower than the total lesions Amiodarone 17 (41) needed to complete the ablation of the circumference in these PV Dronedarone 1 (2) pairs, 21 (IQR: 19–22) vs. 27 (IQR: 26–29) (p < 0.01). LA anatomy (%) Left common trunk 20 (49) Right common trunk 1 (2) Completion of ablation protocol Data are expressed as median (IQR). At the end of the ablation protocol, complete PV isolation LA, left atrium, LVEF, left ventricular ejection fraction. was achieved before the standard ablation circumference Frontiers in Cardiovascular Medicine 06 frontiersin.org Campos-García et al. 10.3389/fcvm.2023.1162197 TABLE 2 Procedural data of ablation in left PVs. Patient # First pass Complete PVI after ablation to Extension of anterior/ Superior ANRA Inferior ANRA PVI anterior/posterior segments posterior ablation needed length (mm) length (mm) 1 Yes Yes No 12.9 18.7 2 Yes Yes No 24.7 23.8 3 Yes Yes No 19.0 18.0 4 Yes Yes No 18.0 15.3 5 Yes Yes No 18.9 23.0 6 Yes Yes No 18.0 24.1 7 Yes Yes No 24.1 27.3 8 Yes Yes No 24.9 18.5 9 Yes No Superior 8.7 26.4 10 Yes Yes No 12.0 13.3 11 Yes Yes No 22.9 17.8 12 Yes No Superior + inferior 9.8 6.7 13 Yes No Superior + inferior 0 0 14 Yes Yes No 22.3 25.0 15 Yes No Superior + inferior 5.6 12.0 16 Yes Yes No 12.2 25.9 17 Yes No Superior 12.0 18.8 18 Yes Yes No 14.3 22.7 19 Yes Yes No 16.4 23.4 20 Yes Yes No 18.3 18.5 21 Yes Yes No 14.0 8.0 22 Yes No Superior + inferior 11.9 14.6 23 Yes Yes No 22.6 25.1 24 Yes Yes No 14.7 22.1 25 Yes Yes No 17.3 17.1 26 Yes Yes No 15.7 24.4 27 No N/A N/A N/A N/A 28 Yes Yes No 26.6 25.2 29 Yes Yes No 9.0 16.2 30 Yes Yes No 20.7 24.0 31 Yes Yes No 17.0 26.5 32 Yes No Superior 9.0 25.0 33 Yes Yes No 20.0 17.0 34 No N/A N/A N/A N/A 35 Yes No Superior 12.0 26.1 36 Yes Yes No 14.0 12.0 37 Yes Yes No 15.9 15.3 38 Yes Yes No 16.1 26.7 39 Yes No Superior 18.6 18.0 40 Yes Yes No 10.5 10.9 41 Yes Yes No 11.5 16.0 ANRA, areas not requiring ablation; PVI, pulmonary vein isolation; N/A, not applicable. around the ipsilateral PVs was closed in 38 (97%) left-PV Discussion pairs and in 33 (94%) right-PV pairs. The number of RF lesions required to achieve PV isolation was significantly The main finding of our study is that ablation of the lower than the total lesions needed to close the standard anterior and posterior regions of the standard ablation ablation circumference around the ipsilateral PVs: 17 (IQR: circumference resulted in complete electrical isolation in 97% 14–19) vs. 25 (IQR: 23–28) in the left PVs and 19 (IQR: of left-PV pairs and in 94% of right-PV pairs, leaving large 16–21) vs. 27 (IQR: 25–29) in the right PVs ( p < 0.01). The areas that did not require ablation (ANRA). This confirms the total length of the ANRA was median 36.9 (IQR: 30.9– hypothesis that the muscle fibers running through these 42.1) mm in the left PVs [16.0 (IQR: 12.0–19.0) mm regions are the main contributors to the electrical connection superior and 18.8 (IQR: 16.1–24.9) mm inferior, p < 0.01] between the LA and the PVs. and 36.9 (IQR: 30.2–41.0) mm in the right PVs [15.1 (IQR: The arrangement of atrial myocardial fibers and their 10.7–19.1) mm superior and 20.6 (IQR: 16.9–23.3) mm contribution to the PV–LA electrical connection is not inferior, p < 0.01] (Figure 6). considered during the circumferential ablation of atrial Frontiers in Cardiovascular Medicine 07 frontiersin.org Campos-García et al. 10.3389/fcvm.2023.1162197 TABLE 3 Procedural data of ablation in right PVs. Patient # First pass Complete PVI after ablation to Extension of anterior/ Superior ANRA Inferior ANRA PVI anterior/posterior segments posterior ablation needed length (mm) length (mm) 1 Yes Yes No 25.3 26.3 2 Yes Yes No 23.2 29.3 3 No N/A N/A N/A N/A 4 Yes No Superior 16.9 23.3 5 Yes No Superior 15.2 33.5 6 Yes Yes No 21.8 24.6 7 Yes No Superior 10.8 21.2 8 Yes Yes No 23.1 28.6 9 Yes No Superior + inferior 12.9 20.3 10 Yes Yes No 20.8 29.3 11 No N/A N/A N/A N/A 12 Yes No Superior 6.2 28.9 13 Yes No Superior + inferior 0 0 14 Yes No Superior 12.4 21.9 15 Yes Yes No 18.0 20.0 16 Yes Yes No 13.3 24.8 17 Yes No Superior 13.2 16.3 18 Yes No Inferior 16.0 0 19 Yes Yes No 19.1 18.0 20 Yes Yes No 10.1 14.3 21 No N/A N/A N/A N/A 22 Yes Yes No 19.0 22.0 23 Yes No Superior 9.5 23.0 24 Yes Yes No 9.0 12.7 25 Yes Yes No 11.8 23.0 26 Yes Yes No 15.9 21.7 27 Yes No Superior 4.8 14.5 28 Yes No Superior 10.0 20.0 29 Yes No Superior + inferior 6.0 13.0 30 Yes Yes No 25.0 16.9 31 Yes No Superior 20.9 16.3 32 No N/A N/A N/A N/A 33 Yes No Superior 13.9 14.5 34 Yes No Superior 10.6 19.6 35 Yes No Superior 10.0 14.0 36 No N/A N/A N/A N/A 37 Yes Yes No 16.9 20.0 38 No N/A N/A N/A N/A 39 Yes Yes No 15.0 21.0 40 Yes Yes No 16.6 20.6 41 Yes Yes No 24.0 17.0 ANRA, areas not requiring ablation; PVI, pulmonary vein isolation; N/A, not applicable. fibrillation. However, we know from anatomical studies that this extensions, mainly directed to the superior veins. Therefore, the arrangement is heterogeneous and complex, with myocardial largest ANRAs were observed at the inferior aspect of both left fibers that are thicker and markedly intermingled in the and right-PV pairs. This finding is consistent with anatomical venoatrial junction near the carina between the ipsilateral PVs, studies showing that muscular sleeves are more extensive around whereas they are thinner or may be even absent in other the superior than around the inferior PVs and that the inferior venoatrial junction regions (Figure 1) (2–5). aspect of the inferior PVs is generally devoid of muscular fibers (2). Our study demonstrates the critical role of the muscular fibers In Figure 3 we illustrate how, after ablation of only the anterior running through the anterior and posterior segments of the and posterior segments of the standard circumference, the low standard ablation circumference for the PV–LA electrical voltage area extends all around the ipsilateral PVs, including the connection, as the initial ablation set, targeting only these upper and lower aspects of the PV pair, where ablation was not segments, was able to isolate up to 77% of the left and 51% of performed (ANRA). Some anatomical features may help us to the right ipsilateral PVs. Interestingly, most of the PV pairs that understand the complete isolation of the ipsilateral pulmonary remained connected were isolated with minimal ablation veins despite leaving large areas unablated. First, the presence of Frontiers in Cardiovascular Medicine 08 frontiersin.org Campos-García et al. 10.3389/fcvm.2023.1162197 longitudinal fascicles along the venoatrial junction with the atrium. Ablation of these regions results in PV isolation in the potential for myocardial continuity between adjacent veins may majority of patients. explain our observation that minimal superior ablation extensions led to the isolation of several inferior PVs and that some inferior ablation extensions also led to the isolation of Data availability statement some superior PVs. Second, myocardial discontinuities related to acquired areas of fibrosis have been described in the myocardial The original contributions presented in the study are included sleeves that enter the PVs. Third, the ostium of the PVs is in the article, and further inquiries can be directed to the surrounded by circular fiber bundles that are arranged corresponding author. transversally to the vein axis. We hypothesize that RF lesions delivered to the anterior and posterior aspects of the ablation circumference could damage these fibers and produce conduction Ethics statement blocks along them (2–5, 9). Our study aims to deepen the knowledge of the electrical The studies involving human participants were reviewed and connection between the PVs and the LA by using an anatomical approved by the Institutional Committee on Human Research at approach. Our data support the major role of the anterior and Hospital Sant Pau. The patients/participants provided their posterior regions of the standard ablation circumference for the written informed consent to participate in this study. Written venoatrial electrical connection. This is particularly relevant at informed consent was obtained from the individuals for the the present time, when the standard approach for PV isolation is publication of any potentially identifiable images or data being redefined in a new era ushered in by single-shot ablation included in this article. techniques, such as the recently emerged pulsed field ablation, which is clinically promising but still has non–well-established protocols of energy delivery along the venoatrial junction. We hope that the information provided by our study will be Author contributions clinically useful and may allow optimization of the standard BC-G, CA-M, and ER-F designed the study. JG-R, ZM-W, FM- approach for PV isolation. Z, RM-Q, AB-G, and XV-P were involved in data collection. BC-G, CA-M, and ER-F performed data analyses and drafted the manuscript. All authors contributed to the article and approved Study limitations the submitted version. The number of patients included in the study is relatively small and reflects their experiences in a single center. The clinical effect of the proposed ablation strategy cannot be Acknowledgments evaluated, since the entire standard circumferential ablation line was systematically completed around the ipsilateral PVs, We thank Jose Angel Cabrera for the histological images included in the article, which undoubtedly help to illustrate the regardless of whether PV isolation had been achieved during the study findings. implementation of the ablation protocol. However, the objective of this study was not to evaluate the clinical impact of this ablation strategy but to determine the regional contribution to the PV–LA electrical connection along the standard ablation Conflict of interest circumference. Our results represent a proof of concept that complete PV isolation may be achieved before the standard The authors declare that the research was conducted in the ablation of the circumference is completed, leaving large areas absence of any commercial or financial relationships that could with no ablation at the time of PV isolation. The clinical effect be construed as a potential conflict of interest. of a PV isolation strategy with ablation restricted to the anterior and posterior regions of the standard circumference around the ipsilateral PVs remains unknown and warrants further study. Publisher’s note All claims expressed in this article are solely those of the Conclusion authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the The myocardial fibers along the anterior and posterior regions reviewers. 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