Atrial Linear Lesions Research Articles

High efficacy and safety of pulsed electrical field ablation via contact force-controlled radiofrequency catheters for atrial fibrillation ablation with linear lesions in the left atrium

Abstract Background Pulsed Field Ablation have been shown to be efficient and safe for Pulmonary vein isolation (PVI) in catheter ablation of atrial fibrillation (AF). The bipolar application of pulsed electrical energy for electroporation of myocardium has been established with specially designed catheters, which are not used for linear ablation. Purpose We evaluated a novel monophasic PEF ablation technique applied by commercially available CF-controlled catheters for linear ablation lines beyond PVI for treatment of complex AF patients. Methods Patients (n=31, age 64±12 years, 29% females, BMI 29±4) referred for re-ablation of AF and presented with recurrence of persistent AF (n=13) or atypical atrial flutter (n=14) after a PVI procedure, or patients with longstanding persistent AF and severe enlarged atrium (n=4) were included in our patient cohort for additional AF substrate ablation with PEF applications. After high density voltage mapping of the left atrium with multipolar microelectrode catheters, and PVI, or re-PVI was completed (8 patients), additional left atrial linear lesions were performed according to the atrial flutter mechanism or as fibrosis-guided substrate ablation. All but one patient showed low voltage areas (bipolar electrograms <0.5mV) in 35±31% of the left atrial surface. Using contact force sensing catheters, maximal PEF energy pulses were applied with a minimum of 5g contact force and an interlesion distance ≤6mm. Performed linear lesions were left atrial roof line, lateral mitral isthmus line, anterior mitral line, left posterior wall isolation, and cavotricuspid isthmus (CTI) line. Before PEF application close-by a coronary artery (lateral mitral line, CTI) nitroglycerie 0.2mg i.v. was injected. Results Complete lines with exclusively PEF applications and proofed bidirectional conduction block were 100% for roof lines (n=20), posterior wall isolation (n=8), anterior mitral lines (n=10). Exclusively endocardial PEF applications blocked the lateral mitral line in 14 out of 16 cases (88%). Only in two cases additional epicardial RF applications via coronary sinus and endocardial additional RF applications were necessary to complete the mitral isthmus block. In 7 out of 8 cases CTI were blocked by linear PEF applications (88%), however, in one case additional RF applications became necessary. No ECG ST segment elevation was recorded. No serious complications occurred throughout all procedures. Follow up will be available at presentation time. Conclusion Catheter ablation of complex AF patients with linear lesions is performd very efficient and safe with PEF applications by CF-sensing RF ablation catheters. Especially the high efficacy of exclusively endocardial PEF applications for creation of a lateral mitral isthmus block is very promising. However, the long term permanence of the linear lines have to be awaited.

Linear lesions for treating the recurrence of persistent atrial tachyarrhythmia after cryoballoon ablation of atrial fibrillation

There is no consensus on the most effective radiofrequency ablation strategy for the initial or repeated treatment of persistent atrial tachyarrhythmia (ATa). To describe success and complication rates after the creation of left atrial (LA) linear lesions for recurrent persistent ATa following an index cryoballoon pulmonary vein isolation (PVI), and to identify predictors of ATa recurrence. During March 2013 to March 2020, we prospectively included all consecutive patients undergoing repeat procedures for the treatment of persistent ATa. Radiofrequency ablation consisting of the creation of linear lesions: a roofline, a mitral isthmus and/or septal line, and a cavotricuspid isthmus line. All patients were prospectively followed up for ATa recurrence. Overall, 133 patients underwent 170 procedures after initial cryoballoon PVI (n=715). At least one pulmonary vein reconnection was observed in 60 patients (45.1%), all of whom underwent successful re-disconnection. After all the procedures, >90% of patients had a lesion pattern consisting of a roofline, a mitral isthmus and/or septal line, and a cavotricuspid isthmus line. ATa was terminated in 41 patients (35%). There were three cases of tamponade (3/170 procedures, 1.8%). Ninety-two patients (69.2%) were in sinus rhythm after a median (interquartile range) of 36 (21-53) months since the index cryoballoon PVI. Diagnosis-to-ablation time and LA area were predictors of recurrence in multivariable analysis. The creation of linear lesions is a safe and effective treatment strategy for the recurrence of persistent ATa after cryoballoon PVI. Longer diagnosis-to-ablation time and larger LA area were predictive of ATa recurrence.

76 Right mini-thoracotomy surgical Cox-maze (left atrial lesion) vs. catheter ablation using contact force-sensing technology in patients with persistent atrial fibrillation

Abstract Aims Pulmonary vein isolation (PVI) often is not sufficient in patients (pts) with persistent atrial fibrillation (AF). Substrate modification (SM) by catheter ablation (CA) of low-voltage zones (LVZ) has yielded favourable results, but those studies were performed before the introduction of contact force (CF) sensing technology. Surgical ablation (SA) studies support the hypothesis that empiric bi-atrial linear ablation (Cox Maze IV procedure) is able to improve success, but there is less data on outcome of patients undergoing left atrial (LA) linear lesions alone. In current guidelines, both CA and SA have Class IIa indication in pts with persistent AF. In this single-centre retrospective study, we analysed the long-term outcomes of CA and SA in pts with persistent AF. Methods and results In the CA group (Figure 1), pts underwent PVI and additional SM in the presence of LVZ (roof line and supero-septal line) using TactiCath™ or SmartTouch™ ablation catheters aiming at contact values ≥10 g < 20 g and FTI >400 g/s. Ablation was performed in a temperature-controlled fashion with energy of 30 W except at the posterior wall (20–25 W). In the SA group (Figure 2), pts underwent ablation procedure (creation of a pure LA endocardial lesion set consistent with the Cox Maze IV) performed by a right mini-thoracotomy approach using the Atricure™ cryoablation probe, a left atrial appendage (LAA) epicardial exclusion using the Atriclip™ system, and mitral valve repair in the presence of severe mitral valve regurgitation. No right atrial lesions were created. 196 pts were included. 120 pts underwent CA [median age: 65 (58–72) years, median LA volume index (LAVI): 66 (56–75) ml/m2], in pts with LVZs PVI + SM was performed [bidirectional block of lines in 100%]. 76 pts underwent SA [median age: 64 (58–74) years, median LAVI 90 (78–103) ml/m2], in 42 pts a mitral valve repair was performed. At 24 months (figure), 89% and 68% of pts were free of AF in the SA and CA group, respectively, mainly without antiarrhythmic drugs (92% SA group and 89% CA group). Conclusions In patients with persistent AF, SA performed by a right mini-thoracotomy approach with linear lesions limited to LA leads to excellent 2-year freedom from AF despite significantly larger LAVI compared with the CA group. LAA epicardial exclusion likely contributed to surgical efficacy by eliminating the LAA as trigger/driver.

High-power and short-duration ablation with the Qdot+ algorithm for pulmonary vein isolation and the right superior ganglion plexus ablation without fluoroscopy

In this report we present pulmonary vein and posterior box isolation together with the right superior ganglion plexus ablation using the Qdot Micro catheter without fluoroscopy. We describe different possibilities of this new technology for catheter ablation. The main advantages of this catheter to potentially increase ablation safety and effectiveness are discussed. Specifically, the possibility to perform high-density mapping with the lowest available distance between points. Furthermore, the possibility to decrease the risk of collateral tissue damage and to improve atrial linear lesions contiguity, transmurality and durability due to the dominance of resistive heating supported by the feedback temperature control. Finally, the possibility to shorten the procedure and fluoroscopy duration due to the high shortening of application duration to 4 seconds only.

Repeat procedures for recurrent persistent atrial fibrillation: A propensity-matched score comparison between left atrial linear ablation with radiofrequency and posterior wall isolation with the cryoballoon.

AimsTo evaluate the clinical outcome in patients undergoing repeat procedures for recurrent persistent atrial fibrillation following an index cryoballoon (CB‐A) pulmonary vein isolation ablation on a mid‐term follow‐up of 12 months.MethodsIn this propensity score‐matched comparison, 50 patients undergoing left atrial posterior wall isolation (LAPWI) with the CB‐A were matched to 50 patients treated with additional linear ablation using radiofrequency catheter ablation (RFCA).ResultsMeantime to repeat the procedure was 9.74 ± 4.36 months. At 12 months follow‐up freedom from atrial tachyarrhythmias (ATas) was achieved in 82% of patients in the LAPWI group and in 62% of patients in the linear ablation group (P = .03). Regression analysis demonstrated that relapses during the blanking period and LA dimensions were independent predictors of ATas recurrences following the repeat procedure.ConclusionLAPWI using CB‐A is associated with a significantly higher freedom from atrial arrhythmias when compared with the RFCA mediated left atrial linear lesions on a mid‐term follow‐up of 12 months in patients with persAF undergoing a redo procedure.

B-PO05-092 RIGHT MINI-THORACOTOMY SURGICAL COX-MAZE IV (LEFT ATRIAL LESION SET) VS CATHETER ABLATION USING CONTACT FORCE-SENSING TECHNOLOGY IN PATIENTS WITH PERSISTENT ATRIAL FIBRILLATION

Pulmonary vein isolation (PVI) often is not sufficient in patients (pts) with persistent atrial fibrillation (PAF). Substrate modification (SM) by catheter ablation (CA) of low-voltage zones (LVZ) has yielded favorable results, but those studies were performed before the introduction of contact force (CF) sensing technology. Surgical ablation (SA) studies support the hypothesis that Cox Maze IV procedure is able to improve success, but there is less data on outcome of pts undergoing left atrial (LA) linear lesions alone. In this single-center retrospective study, we analyzed the long-term outcomes of CA and SA in PAF. In the CA group, pts underwent PVI and additional SM in the presence of LVZ (roof and supero-septal lines) using CF catheters. In the SA group, pts underwent ablation procedure (Cox Maze IV LA endocardial lesion set) performed by a right mini-thoracotomy approach using the Atricure™ cryoablation probe and mitral valve repair in the presence of severe mitral valve regurgitation. 196 pts were included. 120 pts underwent CA (median age 65 [58-72] yrs, median LA volume index (LAVI) 66 [56-75] ml/m2), in pts with LVZs PVI + SM was performed (bidirectional block of lines in 100%). 76 pts underwent SA (median age 64 [58-74] yrs, median LAVI 90 [78-103] ml/m2), in pts mitral valve repair was performed. At 24 months (figure), 89% and 68% of pts were free of AF in the SA and CA group, respectively, mainly without antiarrhythmic drugs (92% SA group, 89% CA group). In PAF, SA performed by a right mini-thoracotomy approach with linear lesions limited to LA leads to excellent 2-year freedom from AF despite significantly larger LAVI compared to the CA group.

B-PO05-093 VALIDATION OF A NEW ABLATION INDEX PROTOCOL FOR LEFT ATRIAL LINEAR ABLATION

Standardized contiguous and optimized radiofrequency ablation encircling ipsilateral pulmonary veins (PV) with high incidence of first-pass isolation has been established with the CLOSE protocol. In this study, we evaluated the acute outcome of a specific ablation index protocol for left atrial (LA) linear ablation. This prospective study comprised 81 patients (age: 67±14 y, male: 52 %) undergoing de-novo ablation for persistent atrial fibrillation (AF) or patients requiring substrate ablation beyond PV isolation. We hypothesized that point-by-point ablation with an ablation index of 600 for the anterior line and 500 for the roof line and an interlesion distance <6mm will result in a high rate of first-pass block. Touch-up ablation was performed in case of incomplete line block. Line integrity was evaluated with a high-density mapping catheter (Pentaray) and the coherent activation mapping tool (CARTO3 V7) during LAA pacing and differential pacing maneuver. First-pass block of the roof line was achieved in 70 (92 %) patients, while another 5 (7 %) patients required additional touch-up ablation to complete the line, resulting in a total of 75 (99 %) blocked roof lines. A first-pass anterior line block was observed in 47 (69 %) patients. An additional 17 (25 %) patients required touch-up ablation for block achievement, resulting in a total of 64 (94 %) blocked anterior lines. For the anterior line, the Bachmann bundle insertion was identified as the predominant location of gaps. The mean ablation index of roof line ablation was 512±14 and 610±13 in anterior line ablation. The mean overall procedure and fluoroscopy time was 136±30 min and 7.2±3.8 min, respectively. The mean RF ablation time for roof line was 8±5.4 min and for anterior line 14±5.9 min. Baseline rhythm was AF in 46 patients, which terminated by linear ablation in 19 (41%) patients. This new standardized Ablation Index protocol accomplishes first-pass block of left atrial linear lesions in the vast majority of patients. Furthermore, with additional touch-up ablation at gap sites, line block was achieved in almost all patients.

Temperature- and flow-controlled ablation/very-high-power short-duration ablation vs conventional power-controlled ablation: Comparison of focal and linear lesion characteristics

The QDOT MICRO catheter allows temperature- and flow-controlled (TFC) ablation and very-high-power short-duration (vHPSD) ablation. The purpose of this study was to compare lesion characteristics between TFC/vHPSD ablation and standard power-controlled (PC) ablation. Lesion characteristics in the right atrium, left atrium, and right ventricle (RV) of 6 sheep were compared between vHPSD (90 W/4 seconds, TC mode with 60°C target using QDOT) and standard radiofrequency settings (PC mode, 30 W/30 seconds with ThermoCool SmartTouch SF). Lesions in the left ventricle (LV) were compared, targeting 50 W for 60-second applications. Forty-six focal atrial lesions, 50 RV focal lesions, and 12 linear lesions were created by vHPSD ablation and PC ablation in each group of 6 animals. vHPSD ablation produced significantly larger focal atrial lesions in length (8.3 [6.4-9.7] mm vs 6.3 [5.2-7.4] mm; P = .0002), width (6.0 [5.3-6.9] mm vs 4.6 [3.8-5.4] mm; P <.0001), and surface area (39.4 [25.4-52.4] mm2 vs 23.6 [16.0-31.1] mm2; P = .0001), with superior transmurality (89.1% vs 69.6%; P = .04) compared to PC ablation. vHPSD ablation produced significantly larger RV lesions in length (7.7 [7.0-8.7] mm vs 6.0 [4.8-6.9] mm; P <.0001), width (6.4 [5.4-7.5] mm vs 4.3 [3.6-5.2] mm; P <.0001), and area (39.4 [29.1-50.1] mm2 vs 19.9 [14.7-25.2] mm2; P <.0001) but similar volume (P = .97) with shallower lesions (2.7 [2.2-3.4] mm vs 3.8 [3.0-4.4] mm; P <.0001). Atrial linear lesions were more homogeneous (P = .02), with fewer gaps in each line (P = .003) with vHPSD ablation. LV focal lesions (15 TFC mode; 21 PC mode) were similar in volume and depth, but lesion size showed less deviation (P <.05) in TFC than PC mode. Fewer steam pops were observed in TFC mode (0% vs 28.6%; P = .03). Hemorrhagic rings around the lesion core were generally smaller with TFC/vHPSD ablation (P <.05). TFC/vHPSD ablation produces larger, shallower, more homogeneous, and less hemorrhagic lesions. vHPSD Ablation produces more transmural and contiguous linear lesions compared to PC ablation. LV lesions are more homogeneous with fewer steam pops in TFC ablation.

Management of thrombus formation after electrical isolation of the left atrial appendage in patients with atrial fibrillation.

Left atrial appendage (LAA) electrical isolation (LAAEI) in addition to pulmonary vein isolation is an emerging catheter-based therapy to treat symptomatic atrial fibrillation. Previous studies found high incidences of LAA thrombus formation after LAAEI. This study sought to analyse therapeutic strategies aiming at the resolution of LAA thrombi and prevention of thromboembolism. Left atrial appendage electrical isolation was conducted via creation of left atrial linear lesions or cryoballoon ablation. Follow-up including transoesophageal echocardiography was conducted. In patients with LAA thrombus, oral anticoagulation (OAC) was adjusted until thrombus resolution was documented. Percutaneous LAA closure (LAAC) under use of a cerebral protection device was conducted in case of medically refractory LAA thrombi. Left atrial appendage thrombus was documented in 54 of 239 analysed patients who had undergone LAAEI. Thrombus resolution was documented in 39/51 patients (72.2%) with available follow-up after adjustment of OAC. Twenty-nine patients underwent LAAC and 10 patients were kept on OAC after LAAEI. No thromboembolic events or further LAA thrombi were documented after 553 ± 443 days of follow-up in these patients. Persistent LAA thrombi despite adaption of OAC was documented in 12/51 patients. One patient remained on OAC until the end of follow-up, while LAAC with a cerebral protection device was performed in 11 patients in the presence of LAA thrombus without complications. Left atrial appendage thrombus formation is common after LAAEI. Adjustment of OAC leads to LAA thrombus resolution in most patients. Left atrial appendage closure in the presence of LAA thrombi might be a feasible option in case of failed medical treatment.

Focal Pulsed Field Ablation for Pulmonary Vein Isolation and Linear Atrial Lesions: A Preclinical Assessment of Safety and Durability.

A novel ablation and mapping system can toggle between delivering biphasic pulsed field (PF) and radiofrequency energy from a 9-mm lattice-tip catheter. We assessed the preclinical feasibility and safety of (1) focal PF-based thoracic vein isolation and linear ablation, (2) combined PF and radiofrequency focal ablation, and (3) PF delivered directly atop the esophagus. Two cohorts of 6 swine were treated with pulsed fields at low dose (PFLD) and high dose (PFHD) and followed for 4 and 2 weeks, respectively, to isolate 25 thoracic veins and create 5 right atrial (PFLD), 6 mitral (PFHD), and 6 roof lines (radiofrequency+PFHD). Baseline and follow-up voltage mapping, venous potentials, ostial diameters, and phrenic nerve viability were assessed. PFHD and radiofrequency lesions were delivered in 4 and 1 swine from the inferior vena cava onto a forcefully deviated esophagus. All tissues were submitted for histopathology. Hundred percent of thoracic veins (25 of 25) were successfully isolated with 12.4±3.6 applications/vein with mean PF times of <90 seconds/vein. Durable isolation improved from 61.5% PFLD to 100% with PFHD (P=0.04), and all linear lesions were successfully completed without incurring venous stenoses or phrenic injury. PFHD sections had higher transmurality rates than PFLD (98.3% versus 88.1%; P=0.03) despite greater mean thickness (2.5 versus 1.3 mm; P<0.001). PF lesions demonstrated homogenous fibrosis without epicardial fat, nerve, or vessel involvement. In comparison, radiofrequency+PFHD sections revealed similar transmurality but expectedly more necrosis, inflammation, and epicardial fat, nerve, and vessel involvement. Significant ablation-related esophageal necrosis, inflammation, and fibrosis were seen in all radiofrequency sections, as compared with no PF sections. The lattice-tip catheter can deliver focal PF to durably isolate veins and create linear lesions with excellent transmurality and without complications. The PF lesions did not damage the phrenic nerve, vessels, and the esophagus.

Cryothermal atrial linear ablation in patients with atrial fibrillation: An insight from the comparison with radiofrequency atrial linear ablation.

Atrial linear lesions are generally created with radiofrequency energy. We sought to evaluate the feasibility of cryothermal atrial linear ablation. Twenty-one atrial fibrillation (AF) patients underwent linear ablation on the left atrial (LA) roof, mitral isthmus (MI), and cavotricuspidisthmus (CTI) with 8-mm-tip cryocatheters following pulmonary vein isolation. The data were compared with those of 31 patients undergoing linear ablation with irrigated-tip radiofrequency catheters. Conduction block was successfully created in 18 of 20 (90%), 9 of 21 (43%), and 20 of 20 (100%) on the LA roof, MI, and CTI by endocardial cryoablation alone with 19.0 (12.0-24.0), 30.0 (23.0-34.0), and 14.0 (14.0-16.0) minute cryo applications, respectively. The presence of either an interposed circumflex artery or pouch at the MI was significantly associated with failed MI block (P = .04). Conduction block was created in 25 of 31 (83.9%), 27 of 31 (87.1%), and 30 of 31 (96.8%) on the roof, MI, and CTI, respectively, by radiofrequency ablation. During the 17.5 (13.0-31.7) months of follow-up, freedom from AF/atrial tachycardia (AT) was significantly higher in the cryo group (P = .05); especially, recurrent AT was more frequent in the RF group (8/31 vs 1/21; P = .03). Conduction block across the roof, MI, and CTI was durable in 6 of 12 (50.0%), 4 of 12 (33.3%), and 9 of 12 (75.0%) patients during second procedures. All nine patients (except one) with recurrent ATs had at least one roof or MI conduction resumption. Cryoablation is effective for creating a roof and CTI linear block, however, creating MI block by endocardial ablation alone was often challenging. Conduction resumption of LA linear block is common and recurrent arrhythmias, especially iatrogenic ATs, are more frequently observed after radiofrequency linear ablation.

A Lattice-Tip Temperature-Controlled Radiofrequency Ablation Catheter: Durability of Pulmonary Vein Isolation and Linear Lesion Block.

This study was designed to evaluate lesion durability on invasive electrophysiologic remapping. The lattice-tip catheter generates a large thermal footprint during temperature-controlled irrigated radiofrequency ablation. In a first-in-human study, this catheter performed rapid point-by-point pulmonary vein isolation (PVI) and other linear atrial ablations. In a prospective 3-center single-arm study, paroxysmal or persistent atrial fibrillation patients underwent PVI and, as needed, linear ablation at the cavotricuspid isthmus (CTI), mitral isthmus (MI), and/or left atrial roof; no other atrial substrate was ablated. Using the lattice catheter and a custom electroanatomic mapping system, temperature-controlled (Tmax 73° to 80°C; 2 to 7 s) point-by-point ablation was performed. Patients were followed for 12months. A total of 65 patients (61.5% paroxysmal/38.5% persistent) underwent ablation: PVI in 65, MI in 22, left atrial roof in 24, and CTI in 48 patients. At a median of 108days after the index procedure, protocol-mandated remapping was performed in 27 patients. The pulmonary veins (PVs) remained durably isolated in all but 1 reconnected PV-translating to durable isolation in 99.1% of PVs, or 96.3% of patients with all PVs isolated. Of 47 linear atrial lesions initially placed during the index procedure, durability was observed in 10 of 11 (90.9%) MI lines, all 11 (100%) roof lines, and all 25 (100%) CTI lines. After a median follow-up of 270days, the 12-month Kaplan-Meier estimate for freedom from atrial arrhythmias was 94.4 ± 3.2%. Temperature-controlled lattice-tip point-by-point ablation showed not only highly durable PVI lesion sets, but also durable contiguity of linear atrial lesions.

Novel mechanisms in the initiation and maintenance of atrial fibrillation: tailored individual treatment

Atrial fibrillation affects approximately three percent of the adults. Ablation strategies targeting the isolation of the pulmonary veins are the up-to-date cornerstones for atrial fibrillation ablations. However, a one-year success rate of repeated interventions is not more than 70%. Long-term efficacy of catheter ablation is presumably limited by electrical and structural remodeling of the atria, which results in a progressive increase in the duration of atrial fibrillation to become sustained. The potential pathophysiological importance of the epicardial adipose tissue, atrial fibrosis, autonomic nervous system and arrhythmogenic foci are documented by several studies. Increased volume, inflammation induced transformation to fibrosis and myocardial infiltration of atrial subepicardial fat in obese patients result in higher risk of atrial fibrillation development. Changes in atrial autonomic innervation under some conditions including regular physical exercise strongly promote arrhythmogenesis via the mechanism of enhanced triggered activity or abbreviated atrial refractoriness. Individualized management of possible trigger and substrate mechanisms are proposed to provide a novel basis for the effective treatment of atrial fibrillation. Pro-fibrotic signalling pathways can be inhibited by the suppression of renin-angiotensin-aldosterone system. Neuromodulation strategies include renal sympathetic denervation and ganglionic plexi ablation. Anticoagulation therapy has also been shown to reduce the burden of abnormal atrial remodeling. Possible novel catheter ablation techniques are used for right or left atrial linear lesions, scar homogenization and catheter ablation of complex fractionated atrial electrograms, rotors or ectopic foci. Beside these new management strategies, clinical consideration of factors of particular risks as obesity, hyperlipidaemia, hypertension, diabetes and obstructive sleep apnoe are also essential. Orv Hetil. 2018; 159(28): 1135-1145.

Lesion Index-Guided Ablation Facilitates Continuous, Transmural, and Durable Lesions in a Porcine Recovery Model.

The Lesion Index (LSI) is a proprietary algorithm from Abbott Medical combining contact force, radiofrequency application duration, and radiofrequency current. It can be displayed during ablation with the TactiCath contact force catheter. The LSI Index was designed to provide real-time lesion formation feedback and is hypothesized to estimate the lesion diameter. Before ablation, animals underwent cardiac computed tomography to assess atrial tissue thickness. Ablation lines (n=2-3 per animal) were created in the right atrium of 7 Göttingen mini pigs with point lesions (25 W). Within each line of ablation, the catheter tip was moved a prescribed distance (D/mm) according to 1 of 3 strategies: D=LSI+0 mm; D=LSI+2 mm; or D=LSI+4 mm. Two weeks after ablation, serial sections of targeted atrial tissue were examined histologically to identify gaps in transmural ablation. LSI-guided lines had a lower incidence of histological gaps (4 gaps in 69 catheter moves, 5.8%) than LSI+2 mm lines (7 gaps in 33 catheter moves, 21.2%) and LSI+4 mm lines (15 gaps in 23 catheter moves, 65.2%, P<0.05 versus D=LSI). ΔLSI was calculated retrospectively as the distance between 2 adjacent lesions above the mean LSI of the 2 lesions. ΔLSI values of ≤1.5 were associated with no gaps in transmural ablation. In this model of chronic atrial ablation, delivery of uninterrupted transmural linear lesions may be facilitated by using LSI to guide catheter movement. When ΔLSI between adjacent lesions is ≤1.5 mm, no gaps in atrial linear lesions should be expected.

Persistency of left atrial linear lesions after radiofrequency catheter ablation for atrial fibrillation: Data from an invasive follow-up electrophysiology study.

Data on the roof line (RL) and mitral isthmus line (MIL) reconnections after atrial fibrillation (AF) catheter ablation (CA) are scarce. We studied the RL and MIL completeness and localization of reconnection sites in consecutive patients after their first-ever AF-CA. We prospectively included 41 consecutive AF patients who underwent predefined lesion sets of two circumferential lines (CLs) for ipsilateral pulmonary vein isolation (PVI) combined with a RL and lateral MIL. Three months after CA, all patients underwent invasive follow-up procedure for line persistency evaluation, irrespective of clinical outcome. At the time of index ablation, PVI-CLs, RL, and MIL was completed in 41 (100%), 39 (95%), and 34 (83%) of patients, respectively. At the 3-month follow-up procedure, reconnections of PVI-CLs, RL, and MIL were found in 61% (25/41), 28% (11/39), and 24% (8/34) of patients, respectively. The 3-month reconnections were located commonly in the anterior and posterior PVI-CL segments, and rarely in the right third of RL and in the posterior part of MIL. The 3-month reconnections were rarely seen at the sites of acute reconnections during index procedure (6%, 20%, and 25% of the PVI-CL segments, RL segments, and MIL segments, respectively). To our knowledge, this is the first study systematically investigating the reconnection of standardized left atrium linear lesions such as RL and MIL after RF-CA for AF in consecutive patients. The RL and MIL 3-month reconnection rates were relatively low (28% and 24%), with poor anatomical concordance between the sites with acute and 3-month reconnections.

Identification of pulmonary vein reconnection gaps with high-density mapping in redo atrial fibrillation ablation procedures.

Maps obtained by means of electroanatomic high-density mapping (HDM) systems have shown their use in the identification of conduction gaps in experimental atrial linear lesion models. The objective of this study was to assess the use of HDM in the recognition of reconnection gaps in pulmonary veins (PV) in redo atrial fibrillation (AF) ablation procedures. One hundred and eight patients were included in a non-randomized study that assessed the recognition of reconnection gaps in PV by means of HDM compared to a control group that received conventional non-fluoroscopic guidance with a circular multipolar catheter (CMC). Among the HDM group, adequate recognition of reconnection gaps was obtained in 60.99% of the reconnected PVs (86 of 141), a figure significantly higher than that achieved with analysis of CMC recorded signals (39.66%, 48 of 121; P = 0.001). The number of applications and total radiofrequency time were also significantly lower in the HDM group (12.46 ± 6.1 vs. 15.63 ± 7.7 and 7.61 ± 3 vs. 9.29 ± 5; P = 0.02, and P = 0.03, respectively). At the 6-month follow-up, no statistically significant differences were found in recurrence of AF or any other atrial tachycardia between the HDM group (8 patients, 14.8%) and the control group in (16 patients, 29.6%; P = 0.104). An analysis of the high-density activation maps allows greater precision in the identification of reconnection gaps in PV, which results in lower radiofrequency time for the new isolation.

Middle-term results of hybrid atrial fibrillation ablation using AtriCure system

IntroductionLong-term results of catheter ablation (CA) for persistent and long-standing persistent atrial fibrillation (AF) are disappointing. The hybrid approach is currently one of options for overcoming the limitations of CA. AimTo evaluate the safety and medium-term efficacy of the hybrid approach in patients with persistent and long-standing persistent AF. MethodsAll patients underwent epicardial thoracoscopic radiofrequency (RF) pulmonary vein (PV) isolation using the AtriCure clamp followed by left atrial (LA) linear lesions (using a linear pen), Marshall ligament disruption, and LA appendage exclusion using an Atriclip. All patients underwent an electrophysiological study (EPS) and RF CA 2–3 months after the initial surgery to eliminate recurrent conductions from/to the PVs or across the linear lesions, and to eliminate all spontaneous and inducible atrial arrhythmias. 7-Day ECG Holter monitoring was performed every 3 months during the first year and every 6 months afterwards to evaluate possible recurrent arrhythmias. ResultsSeventy patients (49 male, median 63.5 years) took part in the study. EPS was performed 87 days (median) after the thoracoscopic surgery. Seventy-six percent of patients were in normal sinus rhythm (SR) at the start of the EPS, 7% had typical atrial flutter, 11% had atrial tachycardia, and 6% were in AF. After completion of the hybrid approach, all PVs were isolated, while a complete conduction block across the linear lines was achieved in 88.6% of patients. Twelve months after the procedure, 77.1% of patients had a stable SR without any anti-arrhythmic medication or re-ablation. If we included those on anti-arrhythmic drugs and re-ablation procedures, SR was achieved in 96.5% of patients during follow-up (936±432 days). ConclusionThe sequential hybrid approach is probably the most effective and relatively safe invasive treatment for persistent and long-term persistent AF with very low medium- to long-term recurrences. Introduction of the hybrid approach to clinical practice requires extensive cooperation between cardiologic and cardiothoracic teams.

Association Between Local Bipolar Voltage and Conduction Gap Along the Left Atrial Linear Ablation Lesion in Patients With Atrial Fibrillation

A bipolar voltage reflects a thick musculature where formation of a transmural lesion may be hard to achieve. The purpose of this study was to explore the association between local bipolar voltage and conduction gap in patients with persistent atrial fibrillation (AF) who underwent atrial roof or septal linear ablation. This prospective observational study included 42 and 36 consecutive patients with persistent AF who underwent roof or septal linear ablations, respectively. After pulmonary vein isolation, left atrial linear ablations were performed, and conduction gap sites were identified and ablated after first-touch radiofrequency application. Conduction gap(s) after the first-touch roof and septal linear ablation were observed in 13 (32%) and 19 patients (53%), respectively. Roof and septal area voltages were higher in patients with conduction gap(s) than in those without (roof, 1.23 ± 0.77 vs 0.73 ± 0.42mV, p= 0.010; septal, 0.96 ± 0.43 vs 0.54 ± 0.18mV, p= 0.001). Trisected regional analyses revealed that the voltage was higher at the region with a conduction gap than at the region without. Complete conduction block across the roof and septal lines was not achieved in 3 (7%) and 6 patients (17%), respectively. Patients in whom a linear conduction block could not be achieved demonstrated higher ablation area voltage than those with a successful conduction block (roof, 1.91 ± 0.74 vs 0.81 ± 0.51mV, p= 0.001; septal, 1.15 ± 0.56 vs 0.69 ± 0.31mV, p= 0.006). In conclusion, a high regional bipolar voltage predicts failure to achieve conduction block after left atrial roof or septal linear ablation. In addition, the conduction gap was located at the preserved voltage area.

Evaluation of the safety and effectiveness of the CryoMedix cryoablation catheter system for the treatment of atrial flutter and fibrillation

Catheter ablation of atrial flutter and fibrillation (AFL and AF) has typically been performed with radiofrequency energy. Cryoablation has recently been used for AF and AFL, but its success has been limited by the nadir temperature achievable using nitrous oxide as a refrigerant. In this study, a novel approach allowing for use of a liquid refrigerant capable of achieving lower nadir temperatures was tested in a canine model with cavo-tricuspid isthmus (CTI) and left atrial (LA) ablation. In six dogs, under general anesthesia, standard catheters were placed in the coronary sinus and right ventricular apex, and the CryoMedix cryoablation catheter (CAC) in the right (CTI) and left atrium (for ablation, across the LA roof, mitral isthmus, and LA septum). Double-freezes up to 2 min each were performed, with a 30-s thaw cycle between freezes. Ablated areas were subsequently grossly inspected and photographed and tissues fixed in formalin for histologic analysis to determine if the lesions were contiguous and transmural. In all animals, long linear (from 4-8 cm) transmural atrial lesions were observed on gross and histological examination in the left atrial roof, septum and mitral isthmus, and across the cavo-trisucpid isthmus. In all animals, bi-directional cavo-tricuspid isthmus block was observed after ablation, during pacing from the coronary sinus ostium and low lateral right atrium, respectively. Up to 50% thickness lesions were observed in the right ventricle below the tricuspid valve in all animals. There were no acute complications noted in any animals. The CAC system produces extremely negative freezing temperatures, significantly lower than those reported for nitrous oxide based systems. The CTI was easily ablated with the CAC system, producing bi-directional conduction block, suggesting a potential role for the system in the treatment of isthmus-dependent atrial flutter. Transmural LA lesions were also produced with the CAC system, suggesting a potential role in treating AF.

Very Long-Term Results of Surgical and Transcatheter Ablation of Long-Standing Persistent Atrial Fibrillation

New hybrid approaches for atrial fibrillation (AF) ablation, combining surgical and percutaneous procedures, are emerging to enhance the long-term success rate of these 2 procedures severally considered. Recent guidelines underline the need for long-term follow-up to really assess the efficacy of AF ablation. From 2000 to 2002, 33 patients with long-standing persistent AF and valvular heart disease underwent valve surgery and cryoablation (pulmonary veins isolation and mitral isthmus and roof line lesions). The surgically created ablation scheme was validated with electroanatomic mapping and percutaneous radiofrequency ablation was performed in case of lesion incompleteness. In 19 of 33 patients (58%) the electroanatomic mapping showed a complete lesion scheme, which increased to 79% (26 of 33) with the addition of radiofrequency ablation. At the mean follow-up of 10.7 ± 3.1 years, 73% (24 of 33) of patients were in sinus rhythm (SR),whereas 27% had permanent AF. At the end of follow-up 81% of patients with a complete lesion scheme were in SR, while 43% with an incomplete one maintained SR (p= 0.048). In patients with long-standing persistent AF and valvular heart disease, the hybrid approach with surgical cryoablation consisting of pulmonary veins isolation and left atrial linear lesions combined with transcatheter radiofrequency ablation was highly effective in maintaining SR for a very long-term follow-up. Electrophysiological evaluation, to validate the transmurality of the surgical lesions and to complete the lesion scheme applying radiofrequency energy, improved the long-term efficacy.