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Background/Objectives: Pulmonary vein isolation (PVI) using radiofrequency catheter ablation with contact force (CF)-sensing technology has improved long-term outcomes in patients with atrial fibrillation. This prospective randomized study aimed to assess the efficacy and safety of CF-sensing technology for additional left atrial (LA) linear ablation of persistent AF (PerAF). Methods: After PVI, anteromitral (AM) line and roof line ablation were performed using a CF-sensing catheter. Patients were randomly assigned to either the CF-sensing (CFS) group or the CF-blind control (Blind) group. The primary endpoint was atrial arrhythmia recurrence. LA late gadolinium enhancement (LA-LGE) MRI was conducted at baseline and 1-year follow-up for long-term lesion evaluation. Results: A total of 62 patients with drug-refractory PerAF were enrolled (mean age: 58 ± 10 years; 77% male). The success rates of AM and roof line block were 97% and 100% in the CFS group (n = 33) and 93% and 90% in the Blind group (n = 29). The time to achieve block was reduced in the CFS group (AM: 36 ± 22 vs. 48 ± 28 min, p = 0.068; roof: 19 ± 14 vs. 27 ± 15 min, p = 0.031). The maximum CF for safety endpoints was significantly lower in the CFS group (AM: 42 vs. 69 g, p < 0.001; roof: 33 vs. 49 g, p = 0.003). Full linear LA-LGE formation on 1-year MRI did not differ significantly between the groups (AM: 17 vs. 36%; roof; 29 vs. 24%, both p = NS). Kaplan–Meier estimates of AF/AT-free survival after ablation procedures were 63.6% in the CFS group and 58.6% in the Blind group (log-rank p = 0.837). Conclusions: In patients with PerAF, additional LA linear ablation following PVI using CF-sensing technology improved procedural safety and reduced the time needed to achieve conduction block. However, it did not significantly influence clinical outcomes or the formation of permanent full linear lesions. [ABSTRACT FROM AUTHOR]

Aim: To explore the safety and efficacy of a novel strategy (bi-atrial linear catheter ablation guided by electrophysiological mapping) for persistent atrial fibrillation (PeAF) treatment. Methods: 83 patients with PeAF were enrolled for evaluation of ablation strategy. 43 patients were subjected to pulmonary vein isolation (PVI) strategy (PVI group). 40 patients were subjected to bi-atrial linear ablation strategy guided by electrophysiological mapping (PVI, left atrial BOX ablation, coronary sinus endocardial linear ablation, tailored left atrial anterior wall linear ablation, mitral isthmus linear ablation with necessary ethanol infusion into the vein of Marshall, right atrial posterior wall linear ablation and cavo-tricuspid isthmus ablation) (linear ablation group). Patients were followed up every 3 months. Results: During a median follow-up of 12 (4–16) months, freedom from atrial fibrillation/atrial tachycardia recurrence was 87.5% in the linear ablation group and 65.1% in the PVI group (P < 0.01). A Cox regression multivariate analysis revealed that ablation strategy group (tailored bi-atrial linear ablation) (HR 0.33, 95% CI 0.12–0.91, P = 0.03) was the only independent predictor of recurrence. Conclusion: Tailored bi-atrial linear ablation strategy guided by electrophysiological mapping resulted in improved outcomes without compromising safety for patients with PeAF. [ABSTRACT FROM AUTHOR]

Background: Maintaining an adequate temperature at the target site is essential for effective ablation. We hypothesized that a tissue temperature‐controlled (T‐Con) catheter for cavotricuspid isthmus (CTI) ablation could improve the procedural ablation parameters. Purpose: To evaluate the efficacy and safety of the T‐Con (DiamondTemp™) catheter for CTI ablation compared with non‐irrigation (Non‐Irri) and irrigation (Irri) catheters. Methods: We analyzed 150 patients who underwent prophylactic CTI ablation combined with pulmonary vein isolation. The Non‐Irri, Irri, and T‐Con catheter groups comprised 50 patients each, and the ablation procedural parameters and complications were compared between these groups. Results: There were no significant differences in clinical background characteristics among the three groups. The Kruskal–Wallis and post hoc tests demonstrated that the T‐Con group showed the lowest total radiofrequency energy delivery time among the three groups (median [25 and 75 percentiles]: 340 [209, 357], 147 [100, 199], and 83 [61, 109] s, respectively in the Non‐Irri, Irri, and T‐Con groups; T‐Con versus Non‐Irri, p <.01; T‐Con versus Irri, p <.01). The total procedural time and acute reconnection rate in the T‐Con group (264 s and 4%, respectively) were lower than those in the Non‐Irri group (438 s and 24%) but were similar to those in the Irri group (268 s and 6%). No significant complications were observed in any group. Conclusions: The T‐Con catheter achieved a short energy delivery time and a low acute reconnection rate, indicating its potential as an alternative catheter for CTI ablation. [ABSTRACT FROM AUTHOR]

Background: Patients may develop atrial tachycardia (AT) after left atrial (LA) ablation of persistent atrial fibrillation (AF). Methods: The population consisted of 101 consecutive patients (age = 64.3 ± 8.7 years, 70 males (69%), LA = 4.6 ± 0.8 cm, ejection fraction = 48.5 ± 16%) undergoing their initial procedure for persistent AF. After pulmonary vein isolation, patients either underwent posterior LA isolation (n = 50; study group) or linear ablation at the LA roof with verification of conduction block (n = 51; control group). Results: A repeat procedure was performed in 17 (34%) and 28 (55%) patients in the study and control groups, respectively (p = 0.02). Patients in the study group were less likely to develop AT (9/50 [18%] vs. 18/51 [35%]; p = 0.02), roof-dependent (1/50 [2%] vs. 8/51 [16%]; p = 0.008), and multi-loop AT (6/50 [12%] vs. 14/51 [27%]; p = 0.03) as compared to controls. Among various factors, only posterior LA isolation was associated with a lower likelihood of AT recurrence and roof tachycardia at redo procedure (OR, 0.37; 95% CI, 0.1 to 1.00, p = 0.05, and OR, 0.1, 95% CI, 0.01 to 0.96; p < 0.05, respectively). Conclusions: In patients with persistent AF, posterior LA isolation is associated with a lower risk of a redo procedure, roof-dependent macro-reentry, and post-ablation AT in general as compared to controls who only received roof ablation. Posterior LA isolation also obviates the need for pacing maneuvers, and may be a more definitive endpoint than linear ablation at the LA roof. [ABSTRACT FROM AUTHOR]

Background: Catheter ablation is routinely used to treat scar-related atrial tachycardia (s-AT). Conventional ablation often involves creating anatomical "lines" that transect myocardial tissue supporting reentry. This can be extensive, creating iatrogenic scar as a nidus for future reentry, and may account for arrhythmia recurrence. High-density mapping may identify "narrower isthmuses" requiring less ablation, with ripple mapping proven to be an effective approach in identifying. This trial explores whether ablation of narrower isthmuses in s-AT, defined using ripple mapping, results in greater freedom from arrhythmia recurrence compared to conventional ablation. Methods: The Ripple-AT-Plus trial (registration ClinicalTrials.gov, NCT03915691) is a prospective, multicentre, single-blinded, randomised controlled trial with 12-month follow-up. Two hundred s-AT patients will be randomised in a 1:1 fashion to either "ripple mapping-guided isthmus ablation" vs conventional ablation on the CARTO3 ConfiDENSE system (Biosense Webster). The primary outcome will compare recurrence of any atrial arrhythmia. Multicentre data will be analysed over a secure web-based cloud-storage and analysis software (CARTONETTM). Conclusion: This is the first trial that considers long-term patient outcomes post s-AT ablation, and whether targeting narrower isthmuses in the era of high density is optimal. [ABSTRACT FROM AUTHOR]

Background: For patients with persistent atrial fibrillation (AF), whether linear ablation should be performed remains controversial, and the efficacy and safety for ablation index (AI)-guided high-energy linear ablation of mitral isthmus (MI) and left atrial (LA) posterior box isolation is still unclear. The aims of this study were to assess the feasibility and clinical success rate of pulmonary veins isolation (PVI) combined with linear ablation of LA roof and posterior inferior (posterior wall isolation) and MI compare with the PVI-alone method in patients of persistent AF. Methods and results: 362 consecutive persistent AF patients were enrolled from two electrophysiology centers. A total of 200 cases were in PVI-plus group and 162 cases were in PVI-alone group. The PVI-alone group received wide circumferential isolation of both ipsilateral pulmonary veins. PVI combined with linear ablation of left atrial posterior wall isolation (LAPWI)and MI were performed in the PVI-plus group. The primary study end point was the first recurrence of an atrial arrhythmia. After 24 months, freedom from the primary endpoint was achieved in 73.5% of the patients in the PVI-plus group and 62.5% in the PVI-alone group (hazard ratio = 0.62, 95% confidence interval: 0.43–0.91, log rank p = 0.012). The procedure-related complication rates were 2.5% in PVI-plus group and 1.9% in PVI-alone group (p = 0.808). Conclusion: In this study, the ablation strategy of ablation (PVI plus linear ablation of mitral isthmus and posterior box isolation) was feasible and safe for persistent AF patients. Compared with the PVI-alone method, it improved outcomes in patients with persistent AF. [ABSTRACT FROM AUTHOR]

Purpose: Based on the high rate of coexisting atrial fibrillation (AF) and atrial flutter (AFL), prophylactic cavotricuspid isthmus ablation (CTIA) adjunctive to AF ablation has recently been attempted in patients with AF and without AFL. The present study aimed to determine the rates of AFL occurrence and CTI reconduction after performing CTI ablation adjunctive to AF ablation.Methods: We analyzed the data of 3833 consecutive patients with AF, who underwent prophylactic CTIA with AF ablation between 2009 and 2020.Results: In all patients, CTIA and AF ablations were successful. Clinical AFL occurred in seven patients (0.18%, 7/3,833), and the observed rate was lower than those reported for cases of AF ablation without CTIA and for those of CTIA for pure AFL. A second ablation was needed in 745 patients at a median of 253 days (25 and 75 percentiles, 116 and 775 days) after the first ablation. In 12.1% (90/745) of the patients, CTI reconduction was observed. The reconduction rate was lower than that previously reported for CTIA for pure AFL.Conclusions: The present retrospective study found acceptably low rates of clinical AFL occurrence and CTI reconduction following prophylactic CTIA performed with AF ablation, which was supported by the findings obtained after performing a comparison of the rates with those of other ablations (AF ablation only and CTIA for pure AFL). Considering the high correlation between AF and AFL, the present study provided information regarding the efficacy of adjunctive CTIA. [ABSTRACT FROM AUTHOR]

Background: The efficacy of pulmonary vein isolation (PVI) alone is not guaranteed for persistent atrial fibrillation (PeAF), and it is unclear which type of ablation approach should be applied in addition to PVI. This study aimed to compare outcomes and prognosis between empirical linear ablation and low-voltage area (LVA) ablation after PVI for PeAF.Methods: We enrolled 128 patients with PeAF who were assigned to the linear ablation group (n = 64) and the LVA ablation group (n = 64) using a propensity score-matched model. After PVI and cardioversion, the patients underwent either empirical linear ablation or LVA ablation during sinus rhythm. All patients in the linear ablation group underwent both roof line and mitral valve isthmus (MVI) ablations. An electrical-guided ablation targeting LVA (< 0.5 mV) was performed in the LVA group. When there was no LVA in the LVA group, only PVI was applied. We compared the procedural outcomes and recurrence after ablation between the two groups.Results: The baseline characteristics were well-balanced between the two groups. Fifty patients had LVA (22 and 28 patients in the linear and LVA groups). The roof and MVI lines were completed in 100% and 96.9% of the patients. During the mean follow-up of 279.5 ± 161.3 days, the LVA group had significantly lower recurrence than the linear group (15 patients [23%] vs. 29 patients [45%], p = 0.014). Thirty-five patients were prescribed antiarrhythmic drugs during the follow-up period (linear group, n = 17; LVA group, n = 18); amiodarone and bepridil were administered to most of the patients (15 and 17 patients, respectively). The difference in the prognosis was relevant among the patients with LVA, while this trend was not observed in those without LVA. The LVA ablation group demonstrated significantly lower radiofrequency energy and shorter procedural time compared to the linear ablation group. The recurrence of atrial flutter was more likely to occur in the linear group than in the LVA group (14 [22%] vs. 6 [9.4%], p = 0.052).Conclusion: The electrophysiological-guided LVA ablation is more effective than empirical linear ablation in PeAF patients with LVA. Unnecessary empirical linear ablation might have a risk of iatrogenic gap and atrial flutter recurrence. [ABSTRACT FROM AUTHOR]

We aimed to evaluate the effect of Bachmann bundle (BB) impairment on electrical and mechanical function of the left atrium (LA), as well as the long-term clinical impact of such impairment. We measured activation time in the five LA walls in 56 patients with atrial fibrillation. LA reservoir, conduit, and contractile function were also evaluated. Patients were divided into two groups based on ablation strategy: the circumferential pulmonary vein isolation (CPVI) group and CPVI with LA anterior wall linear ablation (LAAW) group. Patients in the CPVI + LAAW group were divided into two sub-groups based on ECG differences following ablation: the BB impairment group and intact BB group. LA activation time and function were then compared between the ablation strategy groups and the CPVI + LAAW subgroups. Patients in the CPVI + LAAW group exhibited longer activation times in the anterior and lateral walls of the LA, poorer LA synchrony, and reduced LA contractile and reservoir function when compared with those in the CPVI group. In the BB impairment subgroup, we observed a discrepancy between electrical/mechanical remodeling. Among five walls, activation time was longest in this region. BB impairment was also associated with reduced LA function. Significant changes in LA function and conductibility were observed in patients with anterior wall ablation, especially those with iatrogenic BB impairment. [ABSTRACT FROM AUTHOR]

Aims: Previous studies could not demonstrate any benefit of more intensive ablation in addition to pulmonary vein isolation (PVI) including complex fractionated atrial electrogram (CFAE) and linear ablation for recurrence in the initial catheter ablation of persistent atrial fibrillation (AF). This study aimed to establish the non-inferiority of PVI alone to PVI plus these additional ablation strategies.Methods and Results: Patients with persistent AF who underwent an initial catheter ablation (n = 512, long-standing persistent AF; 128 cases) were randomly assigned in a 1:1 ratio to either PVI alone (PVI-alone group) or PVI plus CFAE and/or linear ablation (PVI-plus group). After excluding 15 cases who did not receive procedures, we analysed 249 and 248 patients, respectively. The primary endpoint was recurrence of AF, atrial flutter, and/or atrial tachycardia, and the non-inferior margin was set at a hazard ratio of 1.43. In the PVI-plus group, 85.1% of patients had linear ablation and 15.3% CFAE ablation. After 12 months, freedom from the primary endpoint occurred in 71.3% of patients in the PVI-alone group and in 78.3% in the PVI-plus group [hazard ratio = 1.56 (95% confidence interval: 1.10-2.24), non-inferior P = 0.3062]. The procedure-related complication rates were 2.0% in the PVI-alone group and 3.6% in the PVI-plus group (P = 0.199).Conclusion: This randomized trial did not establish the non-inferiority of PVI alone to PVI plus linear ablation or CFAE ablation in patients with persistent AF, but implied that the PVI plus strategy was promising to improve the clinical efficacy (NCT03514693). [ABSTRACT FROM AUTHOR]

Introduction: When performing linear ablation, creating contiguous and transmural lesions are technically challenging due to the difficulty in finding electrical conduction gaps. We hypothesized that high‐density mapping could identify the gaps. Methods and Results: This study included consecutive patients who underwent conduction gap mapping of de novo lesions (41 patients, 55 lines) and previous lesions (25 patients, 34 lines). We analyzed the utility of bipolar and unipolar conduction gap mapping and retrospectively assessed the voltage and morphology of the bipolar electrograms at the gap sites. Bipolar and unipolar propagation maps were classified into three types: the propagation wavefront traveled through the linear ablation lesions (direct leak), the wavefront jumped to an opposite site across the line and returned to the line (jump and return leak), and others (indefinite leak). In the jump and return leak maps, the site where it returned suggested a conduction gap site. Bipolar propagation maps identified 30 (54.5%) conduction gaps and unipolar maps identified 40 (72.7%) gaps at de novo linear ablation lesions (P =.01), and 32 (94.1%) gaps and 33 (97.1%) gaps, respectively, at previous lesions (P =.56). Bipolar voltage mapping did not add any further efficacy in detecting conduction gaps, and the morphology of the electrograms recorded at the gap sites was not related to the types of propagation maps. Conclusion: Conduction gaps of linear ablation lesions can be visualized by high‐density mapping with a high probability. Unipolar propagation, when used with bipolar mapping, may help detect conduction gap sites. [ABSTRACT FROM AUTHOR]

Background: Atrial linear lesions are generally created with radiofrequency energy. We sought to evaluate the feasibility of cryothermal atrial linear ablation. Methods and Results: Twenty‐one atrial fibrillation (AF) patients underwent linear ablation on the left atrial (LA) roof, mitral isthmus (MI), and cavotricuspid isthmus (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. Conclusions: 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. [ABSTRACT FROM AUTHOR]

Aims: Achieving block across linear lesions is challenging. We prospectively evaluated radiofrequency (RF) linear ablation at the roof and mitral isthmus (MI) using point-by-point contiguous and optimized RF lesions.Methods and results: Forty-one consecutive patients with symptomatic persistent AF underwent stepwise contact force (CF)-guided catheter ablation during ongoing AF. A single linear set of RF lesions was delivered at the roof and posterior MI according to the 'Atrial LINEar' (ALINE) criteria, i.e. point-by-point RF delivery (up to 35 W) respecting strict criteria of contiguity (inter-lesion distance ≤ 6 mm) and indirect lesion depth assessment (ablation index ≥550). We assessed the incidence of bidirectional block across both lines only after restoration of sinus rhythm. After a median RF time of 7 min [interquartile range (IQR) 5-9], first-pass block across roof lines was observed in 38 of 41 (93%) patients. Final bidirectional roof block was achieved in 40 of 41 (98%) patients. First-pass block was observed in 8 of 35 (23%) MI lines, after a median RF time of 8 min (IQR 7-12). Additional endo- and epicardial (54% of patients) RF applications resulted in final bidirectional MI block in 28 of 35 (80%) patients. During a median follow-up of 396 (IQR 310-442) days, 12 patients underwent repeat procedures, with conduction recovery in 4 of 12 and 5 of 10 previously blocked roof lines and MI lines, respectively. No complications occurred.Conclusion: Anatomical linear ablation using contiguous and optimized RF lesions results in a high rate of first-pass block at the roof but not at the MI. Due to its complex 3D architecture, the MI frequently requires additional endo- and epicardial RF lesions to be blocked. [ABSTRACT FROM AUTHOR]

Abstract: Background: In longstanding persistent atrial fibrillation (LPeAF), the ideal endpoint of ablation remains to be determined. This study was to explore the value of pursuing AF termination or no with the same strategy during ablation on the long‐term outcomes in patients with LPeAF. Methods: Utilized “CCL” strategy is a fixed ablation approach consisting of circumferential pulmonary vein antrum isolation, ablation of complex fractionated atrial electrogram, and linear ablation between two anatomical structures (the mitral isthmus, left atrial roof). Note that 400 patients were randomized to group A (technical endpoint) and group B (pursuing AF termination). Results: A group with technical endpoint had lower rate of acute AF termination (AF→sinus rhythm, 3.5% vs 18.1%; AF→atrial tachycardia, 23.7% vs 44.7%; P < 0.01) and shorter duration of ablation (164.9 ± 20.8 vs 223.4 ± 24.9, P < 0.01), radiofrequency delivery time (69.8 ± 18.1 vs 102.2 ± 26.3, P < 0.01), and x‐ray exposure time (18.2 ± 8.8 vs 27.9 ± 12.4, P < 0.01) than those in B group (pursuing AF termination). During follow‐up, freedom from atrial arrhythmias did not differ between the two groups after a single ablation procedure (46.5% vs 54.3%, P=0.12) and the final ablation procedure (60.1% vs 65.8%, P  =  0.24). Conclusion: In patients of LPeAF, pursuing AF termination during ablation was associated with similar long‐term clinical outcome compared to that with technical endpoint. Ablation to termination is not the best strategy during ablation. [ABSTRACT FROM AUTHOR]

Background Data on the roof line (RL) and mitral isthmus line (MIL) reconnections after atrial fibrillation (AF) catheter ablation (CA) are scarce. Objective We studied the RL and MIL completeness and localization of reconnection sites in consecutive patients after their first-ever AF-CA. Methods 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. Results 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). Conclusions 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. [ABSTRACT FROM AUTHOR]

Aims: This prospective clinical trial was designed to evaluate the efficacy of an ablation strategy, namely '2C3L', in the treatment of persistent atrial fibrillation (AF); and to compare its efficacy with that of the 'stepwise' approach, which has been acknowledged as a promising ablation technique for persistent AF.Methods and Results: The '2C3L' technique is a fixed ablation approach consisting of bilateral circumferential pulmonary vein antrum isolation (PVAI) and three linear ablation lesion sets across the mitral isthmus, left atrial roof, and cavo-tricuspid isthmus. One hundred and forty-six patients with persistent AF were randomized to undergo ablation by using the '2C3L' or the 'stepwise' technique (n = 73, respectively). The primary endpoint was freedom from any atrial tachyarrhythmia off antiarrhythmic drug (AAD) after a single procedure at follow-up. Twelve months after a single procedure, there was no difference in sinus rhythm (SR) maintenance rate between the two groups (67% for '2C3L' vs. 60% for 'stepwise', P = 0.394; 95% confidence interval of between-group difference -8.7 to 22.4%). The procedure (222 ± 42 vs. 263 ± 41 min), fluoroscopy (41 ± 9 vs. 55 ± 8 min), and radiofrequency (RF) (107 ± 32 vs. 128 ± 38 min) time were significantly shorter in the '2C3L' group (all P < 0.001). At 25 ± 5 months after the first procedure, 57.5 and 52.1% of patients from the '2C3L' group and the 'stepwise' group were in SR off AAD (P = 0.494), respectively.Conclusions: For catheter ablation of persistent AF, the '2C3L' strategy is a fixed approach associated with clinical efficacy similar to that of the 'stepwise' approach but with less RF delivery, fewer X-ray exposure, and shorter procedural time. [ABSTRACT FROM AUTHOR]

Consequences of Left Atrial Anterior Wall Linear Ablation Objective As an alternative to the mitral isthmus line (MIL), the left atrial anterior wall line (LAAWL) is effective for the treatment of perimitral flutter. This study evaluated the electrophysiologic and clinical outcomes of LAAWL versus MIL in patients with persistent atrial fibrillation (AF). Methods Two hundred patients with persistent AF were evenly randomized to the LAAWL and MIL groups. After confirming bidirectional block of the line, left atrial appendage (LAA) activation time and LA propagation pattern were assessed during sinus rhythm (SR). Transthoracic and transesophageal echocardiography (TTE and TEE) were performed at 12 months after ablation in patients who remained in stable SR. Results In the 74 patients with LAAWL conduction block relative to the 79 with MIL conduction block, LA propagation contour was markedly changed with delayed LAA potential (longer P-wave onset-to-LAA potential interval: 151.7 ± 19.5 vs. 67.8 ± 18.3 milliseconds, P < 0.001); TTE peak A velocity was lower and LAA emptying wave was delayed in the LAAWL group compared with the MIL group; spontaneous echo contrast (SEC) detected in the LAAWL group was significantly higher than that in the MIL group (15.8% vs. 1.6%, p = 0.0004). During a mean follow-up period of 31.8 ± 9.4 (22-57) months, there were 5 cases of stroke in the LAAWL group, which was significantly different from the MIL group (5% vs. 0%, P = 0.047). Conclusions Complete linear lesions transecting the anterior LA were associated with a significant change in the SR propagation pattern with late activation of LAA. This might result in an increased risk of long-term thrombo-embolism events. [ABSTRACT FROM AUTHOR]

Atrial fibrillation (AF) is the most common sustained arrhythmia worldwide and represents a major burden to health care systems. Atrial fibrillation is associated with a 4- to 5-fold increased risk of thromboembolic stroke. The pulmonary veins have been identified as major sources of atrial triggers for AF. This is particularly true in patients with paroxysmal AF but not always the case for those with long-standing persistent AF (LSPAF), in which other locations for ectopic beats have been well recognized. Structures with foci triggering AF include the coronary sinus, the left atrial appendage (LAA), the superior vena cava, the crista terminalis, and the ligament of Marshall. More than 30 studies reporting results on radiofrequency ablation of LSPAF have been published to date. Most of these are observational studies with very different methodologies using different strategies. As a result, there has been remarkable variation in short- and long-term success, which suggests that the optimal ablation technique for LSPAF is still to be elucidated. In this review we discuss the different approaches to LSPAF catheter ablation, starting with pulmonary vein isolation (PVI) through ablation lines in different left atrial locations, the role of complex fractionated atrial electrograms, focal impulses and rotor modulation, autonomic modulation (ganglionated plexi), alcohol ablation, and the future of epicardial mapping and ablation for this arrhythmia. A stepwise ablation approach requires several key ablation techniques, such as meticulous PVI, linear ablation at the roof and mitral isthmus, electrogram-targeted ablation with particular attention to triggers in the coronary sinus and LAA, and discretionary right atrial ablation (superior vena cava, intercaval, or cavotricuspid isthmus lines). [ABSTRACT FROM AUTHOR]

PV and Linear Ablation for CFAEs. Introduction: Linear ablations in the left atrium (LA), in addition to pulmonary vein (PV) isolation, have been demonstrated to be an effective ablation strategy in patients with persistent atrial fibrillation (PsAF). This study investigated the impact of LA linear ablation on the complex-fractionated atrial electrograms (CFAEs) of PsAF patients. Methods and Results: A total of 40 consecutive PsAF patients (age: 54 ± 10 years, 39 males) who underwent catheter ablation were enrolled in this study. Linear ablation of both roofline between the right and left superior PVs and the mitral isthmus line joining from the mitral annulus to the left inferior PV were performed following PV isolation during AF. High-density automated CFAE mapping was performed using the NAVX, and maps were obtained 3 times during the procedure (prior to ablation, after PV isolation, and after linear ablations) and were compared. PsAF was terminated by ablation in 13 of 40 patients. The mean total LA surface area and baseline CFAEs area were 120.8 ± 23.6 and 88.0 ± 23.5 cm2 (74.2%), respectively. After PV isolation and linear ablations in the LA, the area of CFAEs area was reduced to 71.6 ± 22.6 cm2 (58.7%) (P < 0.001) and 44.9 ± 23.0 cm2 (39.2%) (P < 0.001), respectively. The LA linear ablations resulted in a significant reduction of the CFAEs area percentage in the region remote from ablation sites (from 56.3 ± 20.6 cm2 (59.6%) to 40.4 ± 16.5 cm2 (42.9%), P < 0.0001). Conclusion: Both PV isolation and LA linear ablations diminished the CFAEs in PsAF patients, suggesting substrate modification by PV and linear ablations. (J Cardiovasc Electrophysiol, Vol. 23, pp. 962-970, September 2012) [ABSTRACT FROM AUTHOR]

Abstract: Non-pharmacological rhythm control of atrial fibrillation (AF) is becoming increasingly important in our aging society. Advancement of catheter ablation techniques in the last decade has provided a cure for AF patients, with a nearly established efficiency for paroxysmal cases. However, since ablation of persistent/chronic AF cases is still challenging, early treatment of paroxysmal AF before transformation to the persistent/chronic form is mandatory. Although there is a consensus that pulmonary vein isolation is the first-line approach for ablation of long-standing persistent AF, similar to that for paroxysmal AF, there are still wide variations in the adjunctive approach to modify the atrial substrate of persistent AF (anatomical linear ablation, electrogram-based complex fractionated atrial electrogram ablation, ganglionated plexus ablation, etc.). Since data comparing the effectiveness of these adjunctive approaches are still lacking, large-scale controlled trials evaluating the effect of catheter ablation in diverse patient populations on a long-term basis are needed to establish the appropriate approach for long-standing persistent AF. Furthermore, the development of de novo ablation methods (new energies, new targets, etc.) is expected to improve ablation outcome in patients with long-standing persistent AF. [Copyright &y& Elsevier]

Electrophysiological Change and Mitral Line Block. Background: Achievement of complete conduction block across left mitral isthmus (MI) is a challenging endpoint of linear lesion, and recognizing the precise moment of block is important during ongoing ablation. The objective of this study is to evaluate the changes in P wave morphology and local MI potential at the moment of block during ongoing radiofrequency (RF) application. Methods and Results: We evaluated 69 patients (procedures) in whom successful MI linear conduction block was achieved during coronary sinus (CS) pacing. P wave morphology and/or local MI potential could be evaluated in 64 (93%) and 69 (100%) procedures, respectively. The achievement of MI block was associated with substantial instantaneous changes in 57/69 (82.6%) procedures. P wave morphology changed in 44 (64%) procedures with the change restricted to lateral leads in 39 (57%). Abrupt prolongation of local conduction delay from 106 ± 24 ms to 167 ± 39 ms (P < 0.0001) was observed on proximal bipole of ablation catheter in 34/69 (49.3%) procedures during ongoing RF application. In addition, prolongation of conduction delay was associated with significant change in the electrogram amplitude and polarity in 11 and 19 procedures, respectively. The substantial change in P wave morphology was not observed in any patients without achievement of complete block. Conclusions: The achievement of conduction block across MI line is associated with recognizable changes in the local MI electrograms and the P wave morphology especially in the lateral leads. These instantaneous critical changes may assist catheter ablation and indicate the requirement for prolonged RF application, if necessary. (J Cardiovasc Electrophysiol, Vol. pp. 1-7) [ABSTRACT FROM AUTHOR]

Impact of PFO on LA Linear Ablation. Introduction: We investigated the impact of the mode of left atrial (LA) access via patent foramen ovale (PFO) versus transseptal (TS) puncture on LA linear lesions during atrial fibrillation (AF) ablation. Methods and Results: We investigated 139 (PFO: 25) consecutive patients who underwent mitral isthmus (MI) and/or LA roof linear ablation. Technical endpoint was completeness of linear lesions and duration of radiofrequency (RF) application. During the initial procedure, complete MI and LA roof blocks were created in 13 of 19 (68%) and 14 of 17 (82%) patients in the PFO group, and in 57 of 94 (61%) and 54 of 70 (74%) patients in the TS group, respectively (P = NS). There was no significant difference in RF durations at MI (11.1 ± 8.9 and 15.1 ± 7.6 minutes, P = 0.11), and LA roof (10.1 ± 3.5 and 8.3 ± 5.0 minutes, P = 0.21) between the 2 groups. Among 28 patients who underwent repeat linear ablation, complete MI and LA roof blocks were created in 3 of 4 (75%) and 0 of 1 (0%) patients in the PFO group, and in 16 of 21 (76%) and 7 of 10 (70%) patients in the TS group, respectively (P = NS). There was no significant difference in RF durations at MI (15.3 ± 8.3 and 19.5 ± 18.3 minutes, P = 0.71), and LA roof (19.0 and 10.3 ± 5.4 minutes, P = 0.19) between the 2 groups. Clinical outcomes at 12 months were also similar. Conclusion: There were no significant differences in the procedural success rates, durations of RF application, 12-month clinical outcomes, and complication rates of LA linear ablation between the PFO and TS groups. Accessing the LA via a PFO is not an unfavorable approach toward LA linear ablation. (J Cardiovasc Electrophysiol, Vol. 22, pp. 846-850, August 2011) [ABSTRACT FROM AUTHOR]

LA Linear Ablation With Multielectrode Catheter. Introduction: Creating complete linear block with point-by-point ablation is challenging in the left atrium (LA). The purpose of this study was to evaluate the efficacy of LA linear ablation using a hexapolar linear multielectrode mapping/ablation catheter. Methods and Results: Seventeen patients (age 57 ± 10, 14 male, 6 paroxysmal AF (PAF)) were studied and underwent linear ablation at the mitral isthmus (MI) and LA roof. Ablation was performed with 90 second, 60 °C applications of duty-cycled bipolar/unipolar radiofrequency in a 1:1 ratio simultaneously at all selected electrode pairs. The result could not be evaluated in 2 patients because AF persisted despite cardioversion. Roof line block was confirmed in 9 of 15 (60%) patients. The mean number of applications and the procedural time with and without block was 5.4 ± 2.4 and 4.5 ± 2.2 applications, and 15 ± 8 and 13 ± 7 minutes. MI block was confirmed in 4 of 15 (27%) patients. The mean number of RF applications with and without block was 5.3 ± 2.2 and 9.9 ± 4.4 applications, and the procedural time was 20 ± 9 and 27 ± 10 minutes, respectively. For patients with underlying persistent AF, power was lower than those with PAF but improved when ablation was performed in sinus rhythm. Char was observed in 2 cases; however, no procedure-related complications were observed. Conclusions: In our initial experience, a linear multielectrode catheter using duty-cycled bipolar and unipolar RF energy was inferior to conventional single point irrigated ablation in achieving LA linear block. However, successful linear block was obtained within a short period of time, when it was achieved. (J Cardiovasc Electrophysiol, Vol. 22, pp. 739-745, July 2011) [ABSTRACT FROM AUTHOR]

Aims: Although cavotricuspid isthmus (CTI) ablation can cure typical atrial flutter (AFL), it might be difficult to achieve a bidirectional conduction block in the isthmus in some patients. We investigated the usefulness of a steerable sheath for CTI ablation in patients with typical AFL or atrial fibrillation. [ABSTRACT FROM PUBLISHER]

The seminal observation that ectopics from the pulmonary veins may initiate paroxysmal atrial fibrillation (AF) heralded an era of potentially curative catheter ablation therapy for AF. In recent years, catheter ablation has been performed for not only paroxysmal but also persistent and permanent AF. It is anticipated that the number of procedures will continue to increase and the indication for catheter ablation will expand. This article details our experience with catheter ablation therapy for patients with persistent and chronic AF. [ABSTRACT FROM AUTHOR]

Aims To investigate the effectiveness of additional substrate modification (SM) by left atrial (LA) linear lesions as compared with pulmonary vein isolation (PVI) alone in patients with persistent atrial fibrillation (AF) in a prospective randomized study. Percutaneous PVI has evolved as an accepted treatment for paroxysmal AF but seemed to be less effective in patients with persistent AF. The benefit of PVI alone and additional linear lesions has not been validated in a randomized study so far. [ABSTRACT FROM PUBLISHER]

Background: Left atrial (LA) linear lesions are effective in substrate modification for atrial fibrillation (AF). However, achievement of complete conduction block remains challenging and conduction recovery is commonly observed. The aim of the study was to investigate the localization of gap sites of recovered LA linear lesions. Methods and Results: Forty-eight patients with paroxysmal (n = 26) and persistent/permanent (n = 22) AF underwent repeat ablation after pulmonary vein (PV) isolation and LA linear ablation at the LA roof and/or mitral isthmus due to recurrences of AF or flutter. In 35 patients, conduction through the mitral isthmus line (ML) had recovered whereas roof-line recovery was observed in 30 patients. The gaps within the ML were distributed to the junction between left inferior PV and left atrial appendage in 66%, the middle part of the ML in 20%, and in 8% to the endocardial aspect of the ML while only 6% of lines showed an epicardial site of recovery. The RL predominantly recovered close to the right superior PV (54%) and less frequently in the mid roof or close to the left PV (both 23%). Reablation of lines required significantly shorter RF durations (ML: 7.24 ± 5.55 minutes vs 24.08 ± 9.38 minutes, RL: 4.24 ± 2.34 minutes vs 11.54 ± 6.49 minutes; P = 0.0001). Patients with persistent/permanent AF demonstrated a significantly longer conduction delay circumventing the complete lines than patients with paroxysmal AF (228 ± 77 ms vs 164 ± 36 ms, P = 0.001). Conclusions: Gaps in recovered LA lines were predominantly located close to the PVs where catheter stability is often difficult to achieve. Shorter RF durations are required for reablation of recovered linear lesions. Conduction times around complete LA lines are significantly longer in patients with persistent/permanent AF as compared to patients with paroxysmal AF. [ABSTRACT FROM AUTHOR]

Introduction: Nonpulmonary vein sources have been implicated as potential drivers of atrial fibrillation (AF). This observational study describes regions of fibrillating atrial tissue isolated inadvertently from the left atrium (LA) following linear catheter ablation for AF. Methods and Results: We report four patients with persistent/permanent AF who underwent pulmonary vein isolation with additional linear lesions and who presented with recurrent AF (mean AF cycle length [AFCL] 175–270 ms). Further catheter ablation resulted in the inadvertent electrical isolation of significant areas of the LA in which AF persisted at the same AFCL as was measured prior to disconnection, despite the restoration of sinus rhythm (SR) in all other left and right atrial areas, strongly suggesting that these islands were driving the remaining atria into fibrillation. The disconnected areas were located in the lateral LA, including the left atrial appendage (LAA) in three patients (limited to the LAA in one) and in the posterior LA in one patient. These isolated fibrillating regions represented 15–24% of the global LA surface, as estimated by electroanatomic mapping. Conclusion: Fibrillation can be maintained within electrically isolated regions of the LA following catheter ablation of AF, demonstrating the importance of atrial drivers in the maintenance of AF. Further mapping of these drivers is needed to characterize their mechanism and thereby allow for a more specific ablation strategy. [ABSTRACT FROM AUTHOR]

Creating Continuous Linear Lesions. Introduction: Catheter-based treatment of atrial fibrillation (AF) requires the isolation of the triggering foci as well as modification of the atria with substrate that sustains AF. The creation of linear lesions in the left atrium with standard radiofrequency ablative methods requires long procedural times with unpredictable results. Methods: The simultaneous delivery of phase-shifted radiofrequency energy from a multipolar catheter was compared to the conventional drag-and-burn technique for creating linear lesions in 10 dogs. Four atrial sites were targeted under intracardiac ultrasound and fluoroscopic guidance in each of 10 dogs. The conventional drag-and-burn technique or the multipolar phase-shifted ablation catheter was randomly applied for 60 seconds and compared. Results: Creating linear lesions using the simultaneous multipolar phase-shifted ablation catheter was on average 11.0 minutes faster (33.6 minutes vs 44.6 minutes, P < 0.01) than the drag-and-burn method. The fraction of the lesion length achieved using phase-shifted ablation compared to that intended was 23% greater (76% vs 53%, P < 0.01), and has less discontinuities (0.1 compared to 0.8 discontinuities/line, P < 0.003). There was no significant difference in either the lesion transmurality, or fluoroscopy times. Conclusion: The simultaneous delivery of phase-shifted, radiofrequency energy using a multipolar catheter is more effective and efficient in producing linear lesions than the traditional drag-and-burn technique. Using the multipolar ablative method to create linear lesions may be a useful technique in the treatment of patients with substrate-mediated atrial fibrillation. (J Cardiovasc Electrophysiol, Vol. 16, pp. 1-7, July 2005) [ABSTRACT FROM AUTHOR]

Aims Catheter ablation of atrial fibrillation (AF) is centred on pulmonary vein (PV) ablation with or without additional atrial substrate modification. These procedures may be prolonged with significant fluoroscopy exposure. This study evaluates a new non-fluoroscopic navigation system during ablation of AF. [ABSTRACT FROM PUBLISHER]

Linear Ablation and Pacing Site in AF Prevention. Introduction: Right atrial linear lesions (RALL), either alone or in combination with antiarrhythmic drug therapy, may modify the substrate for maintenance of atrial fibrillation (AF). The aim of this prospective randomized study was to determine whether RALL provides additional benefit to right atrial appendage pacing (RAAP) and/or interatrial septum pacing (IASP) and drug therapy in patients with symptomatic paroxysmal AF and sinus bradycardia requiring permanent atrial pacing. Methods and Results: Sixty-four patients (33 men and 31 women, mean age 73 ± 10 years ) completed the 6-month follow-up. Patients were randomized to either RALL (n = 33) or non-right atrial linear lesions (NRALL), and then to either IASP (n = 32) or RAAP (n = 32) . Fifteen RALL patients were paced at the IAS and 18 at the RAA. Seventeen NRALL patients were paced at the IAS and 14 at the RAA. No statistical difference was observed with regard to the mean atrial tachyarrhythmia (AT) burden between NRALL (84 ± 169 min/day) and RALL patients (202 ± 219 min/day) . Mean AT burden was significantly lower in the IASP group (70 ± 150 min/day) than in RAAP group (219 ± 317 min/day; P < 0.016) . In the RALL group, the mean AT burden was 99 ± 180 min/day in the IASP patients and 288 ± 372 min/day in the RAAP patients (P < 0.046) . In the NRALL group, no statistical difference in the mean AT burden was observed between IASP patients (46 ± 117 min/day) and RAAP patients (130 ± 211 min/day) . Conclusion: The results of the present study indicate that RALL did not provide any additional therapeutic benefit to combined antiarrhythmic drug therapy and septal or nonseptal atrial pacing in patients with sinus bradycardia and paroxysmal AF. (J Cardiovasc Electrophysiol, Vol. 14, pp. 733-738, July 2003). [ABSTRACT FROM AUTHOR]

Background: Catheter based “maze” procedures for atrial fibrillation have been hampered by difficult creation and evaluation of continuous and transmural linear lesions. Our aim was to develop an online evaluation method for effective lesion creation based on conventional techniques and using the multipolar ablation catheter, already in place. Methods and Results: We created 15 linear lines in right atria of 13 anesthetized sheep using three multipolar catheter designs (8 × 4 mm 7 Fr, 4 × 6 mm 7 Fr, 8 × 4 mm 3.7 Fr). The lesions were placed on the right posterolateral wall between the orifices of the superior and inferior vena cava. Radiofrequency energy was applied in the temperature-controlled mode to prespecified endpoints (electrogram amplitude decrease to ≤50%; pacing threshold increase by ≥100%; split potentials indicating conduction block). Macroscopically transmural and continuous lesions were achieved in only 3 experiments (29 ± 12 mm × 5 ± 1 mm), all created by 3.7 Fr octapolar catheters inserted through long sheaths. Preset temperature was reached in 96% of the electrodes (vs. 64% in the non-effective experiments; p < 0.01). Electrogram amplitude decrease (to ≤50%) and pacing threshold increase (by ≥100%) did not predict effectiveness. The only criterion that could reliably predict transmural continuous necrosis at histology was the development of split potentials (p ≤ 0.05). Conclusions: Effective creation of linear lesions is difficult. Pliable catheters that conform to the endocardial contour give the best results. The only endpoint that reliably predicted histological transmural continuous necrosis was development of split potentials indicating conduction block. [ABSTRACT FROM AUTHOR]

Pre-ablation impedance was evaluated for its ability to detect electrode-tissue contact and allow creation of long uniform linear lesions with a multi-electrode ablation catheter. The study consisted of 2 parts, both of which used the in vivo pig thigh muscle model. In part 1, a 7 Fr. multi-electrode catheter was held in 3 electrode-tissue contact conditions: (1) non-contact; (2) light contact with a 30[emsp4 ]g downward force; and (3) tight contact with a 90[emsp4 ]g downward force. Impedances were measured in unipolar, modified unipolar and bipolar configurations using a source with frequencies from 100[emsp4 ]Hz to 500[emsp4 ]kHz. Compared with non-contact, the impedance increased 35±22±% with 30[emsp4 ]g contact pressure and 68±40±% when the contact pressure was increased to 90[emsp4 ]g across the range of frequencies studied. In part 2, the same catheter was held against the tissue with different forces. Pre-ablation impedance was measured using a 10[emsp4 ]kHz current. Phased radiofrequency energy was applied to the 5 electrodes simultaneously using 10[emsp4 ]W power at each electrode for 120[emsp4 ]s. A total of 32 linear lesions were created. The lesion dimensions correlated with pre-ablation impedance. A unipolar impedance ≥190[emsp4 ]Ω indicates 95±% possibility to create a uniform linear lesion of at least 3[emsp4 ]mm depth with our ablation system. We conclude that pre-ablation impedance may be a useful indicator for predicting electrode-tissue contact and the ability to create a continuous and transmural linear lesion with a multi-electrode catheter. [ABSTRACT FROM AUTHOR]

Recent observations regarding the mechanisms of chronic atrial fibrillation (CAF) plus a few encouraging clinical reports have created a paradigm shift regarding treatment strategies and the potential for restoring normal sinus rhythm (NSR) utilizing available catheter-based ablation techniques. The initial and late follow-up clinical experience with a two-staged biatrial linear and focal radiofrequency ablation (BALF I, II) procedure to restore NSR in patients with GAP are described. Pre-BALF management included confirming drug refractoriness and optimizing anticoagulation therapy. BALF I and II were preceded by transesophageal echocardiography to exclude thrombus. Femoral venous catheters were placed in the left atrium and the right atrium with extensive left atrial mapping, ablation (linear and focal) and more limited right atrial ablation. Localized electrogram recordings demonstrated rapid, localized, stable focal driving rotors (FDRs) in the left atrium (nine patients) and in the right atrium (one patient). A trial or intraatrial tachycardia (IAT) commonly recurred after HALF I, BALF II addresses these recurrences by repeat mapping and ablation techniques. There were no thromboembolic complications. Two patients developed pericardial tamponade that responded to medical management. Of the 11 patients with late follow-up data, 9 have NSR, atrial function, and are no longer experiencing C4F. Left atrial ablation lines decrease continuous electrogram activity, probably isolate portions of the atrium, and unmask FDRs. Focal and linear ablations appear helpful in transforming CAF to NSR. FDRs are commonly localized to pulmonary vein ostium, trabeculated portions of the atrium, and left atrial appendage. [ABSTRACT FROM AUTHOR]

Recently, a novel linear multielectrode mapping/ablation catheter was developed. We present a case in which mitral isthmus line ablation was undertaken with this catheter and showed repeated conduction recovery at the same site on the line. Mapping with this multielectrode catheter along the whole lesion allowed recording of abrupt conduction resumption. [ABSTRACT FROM PUBLISHER]

An ongoing multicenter U.S. clinical study evaluates the safety and effectiveness of creating linear lesions with radiofrequency (RF) energy using a 3.7 Fr microcatheter used with a 9 Fr steerable guiding catheter in the right atrium (RA) to treat paroxysmal atrial fibrillation (PAF). Study entry criteria were symptomatic, drug refractory PAF. RF energy was delivered in 60-second episodes at 30 W or 50 W power settings. Electrode tissue con tact was ascertained by sharp electrograms of high amplitude. Coagulum Index (C.I.), a new calculation to predict the probability of coagulum development, was derived analytically from measurements of RF power, RF current, and time to reach maximum temperature in each ablation episode. The RF data from 398 separate ablation episodes in 15 patients were used to calculate C.I. Coagulum presence was determined by postablation visual inspection of the microcatheter electrodes. A logistic model was used to estimate the probability of coagulum occurrence, with C.I. as the predictive variable. When C.I. ≥ 12, the probability of coagulum formation increased significantly in this model (P < 0.0001). Prolonging the power delivery rise time and limiting maximum RF power setting to 30 W effectively lowers C.I. and minimizes coagulum formation. These results should also apply to left atrium ablation, where minimizing coagulum formation may decrease the risk of stroke or mortality. [ABSTRACT FROM AUTHOR]