The Role of α7nAChR-Mediated Cholinergic Anti-Inflammatory Pathway in Vagal Nerve Regulated Atrial Fibrillation.

The aim was to investigate the role of the α7nAChR-mediated cholinergic anti-inflammatory pathway in vagal nerve regulated atrial fibrillation (AF).18 beagles (standard dogs for testing) were used in this study, and the effective refractory period (ERP) of atrium and pulmonary veins and AF inducibility were measured hourly during rapid atrial pacing at 800 beats/minute for 6 hours in all beagles. After cessation of 3 hours of RAP, the low-level vagal nerve stimulation (LL-VNS) group (n = 6) was given LL-VNS and injection of salinne (0.5 mL/GP) into four GPs, the methyllycaconitine (MLA, the antagonist of α7nAChR) group (n = 6) was given LL-VNS and injection of MLA into four GPs, and the Control group (n = 6) was given saline into four GPs and the right cervical vagal nerve was exposed without stimulation. Then, the levels of the tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), acetylcholine (ACh), STAT3, and NF-κB proteins were measured. During the first 3 hours of RAP, the ERPs gradually decreased while the dispersion of ERPs (dERPs) and AF inducibility gradually increased in all three groups. During the last 3 hours of 6 hours' RAP in this study, the ERPs in the LL-VNS group were higher, while the dERPs and AF inducibility were significantly lower when compared with the Control and MLA groups at the same time points. The levels of ACh in the serum and atrium in the LL-VNS and MLA groups were higher than in the Control group, and the levels of TNF-α and IL-6 were higher in the Control and MLA groups than in the LL-VNS group. The concentrations of STAT3 in RA and LA tissues were higher in the LL-VNS group while those of NF-κB were lower.In conclusion, the cholinergic anti-inflammatory pathway mediated by α7nACh plays an important role in low-level vagal nerve-regulated AF.

Heart rate increase after pulmonary vein isolation predicts freedom from atrial fibrillation at 1 year.

INTRODUCTION: Ablation of atrial vagal ganglia has been associated with improved pulmonary vein isolation (PVI) outcomes. Disruption of vagal reflexes results in heart rate (HR) increase. We investigated the association between HR change after PVI and freedom from atrial fibrillation (AF) at 1 year. METHODS AND RESULTS: Patients who underwent PVI for paroxysmal AF were identified from the Johns Hopkins Hospital AF registry. Electrocardiograms taken pre-PVI and post-PVI were used to determine the change in HR. Patients followed-up at 3, 6, and 12 months. Of 257 patients (66% male, age 59+/-11 years), 134 (52%) remained free from AF at 1 year. The average HR increased from 60.6 ± 11.3 beats per minute (bpm) pre-PVI to 70.7 ± 12.0 bpm post-PVI. Patients with recurrence of AF had lower post-PVI HR than those who remained free from AF (67.8 ± 0.2 vs 73.3 ± 13.0 bpm; P <.001). The probability of AF recurrence at 1-year decreased as the change in HR increased (estimated odds ratio [OR], 0.83; 95% confidence interval [CI, 0.74-0.93]; P = .002). HR increase more than 15 bpm was associated with the lowest odds of AF recurrence (estimated OR, 0.39; 95% [0.17-0.85]; P = .018) compared to HR decrease. CONCLUSIONS: Resting HR was found to increase after PVI. Increase in HR more than 15 bpm has a positive association with remaining free from atrial fibrillation at 1 year.

Pacemaker Implantation After Mitral Valve Surgery With Atrial Fibrillation Ablation.

BACKGROUND: The incidence of permanent pacemaker (PPM) implantation is higher following mitral valve surgery (MVS) with ablation for atrial fibrillation (AF) compared with MVS alone. OBJECTIVES: This study identified risk factors and outcomes associated with PPM implantation in a randomized trial that evaluated ablation for AF in patients who underwent MVS. METHODS: A total of 243 patients with AF and without previous PPM placement were randomly assigned to MVS alone (n = 117) or MVS + ablation (n = 126). Patients in the ablation group were further randomized to pulmonary vein isolation (PVI) (n = 62) or the biatrial maze procedure (n = 64). Using competing risk models, this study examined the association among PPM and baseline and operative risk factors, and the effect of PPM on time to discharge, readmissions, and 1-year mortality. RESULTS: Thirty-five patients received a PPM within the first year (14.4%), 29 (83%) underwent implantation during the index hospitalization. The frequency of PPM implantation was 7.7% in patients randomized to MVS alone, 16.1% in MVS + PVI, and 25% in MVS + biatrial maze. The indications for PPM were similar among patients who underwent MVS with and without ablation. Ablation, multivalve surgery, and New York Heart Association functional (NYHA) functional class III/IV were independent risk factors for PPM implantation. Length of stay post-surgery was longer in patients who received PPMs, but it was not significant when adjusted for randomization assignment (MVS vs. ablation) and age (hazard ratio [HR]: 0.81; 95% confidence interval [CI]: 0.61 to 1.08; p = 0.14). PPM implantation did not increase 30-day readmission rate (HR: 1.43; 95% CI: 0.50 to 4.05; p = 0.50). The need for PPM was associated with a higher risk of 1-year mortality (HR: 3.21; 95% CI: 1.01 to 10.17; p = 0.05) after adjustment for randomization assignment, age, and NYHA functional class. CONCLUSIONS: AF ablation, multivalve surgery, and NYHA functional class III/IV were associated with an increased risk for permanent pacing. PPM implantation following MVS was associated with a significant increase in 1-year mortality. (Surgical Ablation Versus No Surgical Ablation for Patients With Atrial Fibrillation Undergoing Mitral Valve Surgery; NCT00903370).

Quantification of acute parasympathetic denervation during cryoballoon ablation by using extracardiac vagal stimulation.

AIMS: The purpose of this study was to systematically quantify the level of acute parasympathetic denervation in a stepwise fashion by means of extracardiac vagal stimulation (ECVS) by positioning a quadripolar catheter in the internal jugular vein, in a cohort of patients undergoing second-generation cryoballoon ablation for paroxysmal atrial fibrillation. METHODS: Fifty patients with symptomatic paroxysmal atrial fibrillation, having undergone extracardiac vagal stimulation before and after ablation by means of second-generation cryoballoon second-generation cryoballoon ablation, were included. RESULTS: The extracardiac vagal stimulation performed preablation provoked cardioinhibitory responses in all patients with mean pause duration of 10130.6 ± 3280.0 ms. At the end of the procedure, the VRs were significantly diminished with mean pause of 1687.5 ms ± 2183.7 ms (P = 0.00 compared with the pause before the procedure). CONCLUSION: The ECVS proved to be a reproducible, feasible and reliable method to quantify the degree of parasympathetic denervation during CB-A. In all patients, significant cardiac parasympathetic denervation could be observed at the end of the procedure. Responses to ECVS were more specific to quantify the vagal denervation than the increase in the heart rate. However larger studies are needed to confirm this observation.

Quantitative Analysis of the Isolation Area During the Chronic Phase After a 28-mm Second-Generation Cryoballoon Ablation Demarcated by High-Resolution Electroanatomic Mapping.

BACKGROUND: The post-second-generation cryoballoon (CB) ablation isolation area during the chronic phase has not been described. The aim of this study was to quantitatively evaluate the chronic-phase isolation area after 28-mm second-generation CB ablation and compare it to the estimated conventional radiofrequency circumferential pulmonary vein isolation (CPVI) line. METHODS AND RESULTS: Thirty-two patients with paroxysmal atrial fibrillation underwent pulmonary vein (PV) isolation using second-generation CB. After a median of 6.0 (4.0-9.0) months, the PV isolation area was evaluated using high-resolution mapping (1-mm electrode, 2-mm interelectrode spacing; 527±99 points per map) and pacing techniques in all patients (17 with and 15 without arrhythmia recurrence beyond blanking period) and compared with estimated conventional radiofrequency CPVI area. PV reconnections were observed in 34 of 126 PVs (27.0%) among 21 of 32 patients (65.6%), which were eliminated by a median of 1.0 (1.0-3.0) focal radiofrequency application. The left- and right-sided PV antrum isolation area and nonablated posterior wall areas were 9.8±1.7, 8.1±2.3, and 17.0±6.1 cm(2), respectively. The cryoablated areas were significantly smaller than the estimated conventional radiofrequency CPVI areas in all but the right inferior PV. The difference was highest in the left superior PV. In 2 patients (6.3%), recurrent atrial fibrillation originated from the foci identified at the left superior PV antrum outside the CB isolation area but inside the estimated conventional radiofrequency CPVI line. CONCLUSIONS: Although the PV isolation areas during the chronic phase after the second-generation CB ablation were generally wide, they were significantly smaller than the area encircled by the CPVI line except at the right inferior PV antrum. Recurrent atrial fibrillation could originate from the left superior PV antrum and could be isolated by a CPVI but not by a CB.

[Predictors of Efficacy of Radiofrequency Ablation of Pulmonary Veins Performed During Coronary Bypass Surgery in Patients With Ischemic Heart Disease and Paroxysmal Atrial Fibrillation].

We performed simultaneous coronary artery bypass grafting (CABG) and radiofrequency ablation (RFA) ostia of pulmonary veins in 254 patients (147 men and 107 women) with ischemic heart disease and paroxysmal atrial fibrillation (AF). In-hospital mortality in patients with early recurrence of AF was 8.4%, in patients without recurrence of AF 1.9% (χ2 = 4.65; p = 0.03). The patients were followed-up during 12 months after operation. During follow-up 166 patients (69.5%) had no recurrence of AF without receiving antiarrhythmic drugs (AAP), 33 patients (13.8%) had recurrences of AF, and 40 patients (16.7%) receiving AAD had repeated rare paroxysms of AF. Main predictors of late AF recurrence were age > 65 years, AF duration > 5 years, preoperative atrial effective refractory period < 240 ms, frequency threshold of AF induction < 400 counts/min, anteroposterior left atrial size > 50 mm, glomerular filtration rate < 60 ml/min/1.73 m2. Reverse dynamics of structural, functional and electrophysiological parameters of the heart due to CABG and RFA, use of ß-blockers, angiotensin converting enzyme inhibitors and aldosterone antagonists were associated with the preservation of a stable sinus rhythm. The cardiovascular mortality during 12 months follow-up accounted for 2.1% and 1.2% in groups of patients with and without late recurrences of AF respectively (p > 0.05) to coronary artery bypass grafting surgery and RFA, taking drugs--ß-blockers, angiotensin converting enzyme inhibitors and aldosterone antagonists--were associated with the preservation of a stable sinus rhythm.

The Hot and the Cold: Radiofrequency Versus Cryoballoon Ablation for Atrial Fibrillation.

Catheter ablation is superior to antiarrhythmic drugs in maintaining sinus rhythm for patients with atrial fibrillation (AF). Pulmonary vein (PV) isolation is the cornerstone of any AF ablation procedure. Conventionally, this is achieved by performing point by point lesions using radiofrequency (RF) energy. However, this is technically challenging, time consuming and is associated with a number of complications. Long-term durability of PV isolation is also a concern. To address these issues, 'one-shot' energy delivery systems and alternative energy sources have been developed. The cryoballoon system has emerged as the most commonly used alternative to point by point RF technology. In this paper, we compare the technology, biophysics and clinical data of cryoballoon to conventional RF ablation for AF. The safety and efficacy of cryoballoon compared to RF ablation is critically reviewed. We conclude by looking at future applications of this technology.

Electrical connection between ipsilateral pulmonary veins: prevalence and implications for ablation and adenosine testing.

BACKGROUND: Anatomic studies have reported the presence of shared myocardial fibers between approximately half of ipsilateral pulmonary veins (IPVs). OBJECTIVE: The purpose of this study was to assess the prevalence of electrical connection between IPVs and the impact of antral isolation with or without carina ablation on IPV connection. METHODS: Thirty consecutive patients undergoing atrial fibrillation (AF) ablation (14 redo) were included. Wide antral pulmonary vein isolation (PVI) was performed with or without carina lesions. For each PV set, IPV electrical connection was assessed before and after PVI by pacing and recording from the ostium of both IPVs using a circular mapping catheter and the ablation catheter. Adenosine was given after PVI to assess for acute PV reconnection. RESULTS: Before PVI without preceding AF ablation procedure, all the PVs had ipsilateral connection albeit frequently via the left atrium. After PVI, 65.6% of the IPVs were connected without carina ablation vs 17.7% if prior carina ablation (P = .001). Left vs right IPVs were connected in 57.1% and 72.2% of the cases without carina ablation, respectively, vs 30% and 0% of cases with carina ablation (P = .19 and P = .001). When transient PV reconnection was demonstrated during adenosine challenge, connected IPVs uniformly demonstrated simultaneous reconnection. CONCLUSION: Electrical connection between IPVs is uniformly demonstrated before any ablation. Two-thirds of the IPVs are connected after antral PVI, and carina ablation decreases IPV connection. Connected IPVs consistently show the same response to adenosine challenge; therefore, a single catheter positioned in either of the IPVs with electrical connection is sufficient to confirm reconnection in both veins.

The independent role of the aortic root ganglionated plexi in the initiation of atrial fibrillation: An experimental study.

OBJECTIVE: The major atrial ganglionated plexi (GP) can initiate atrial fibrillation alone without any contribution from the extrinsic cardiac nervous system. However, if stimulation of the ventricular GP, especially the aortic root GP, can provoke atrial fibrillation (AF) alone is unknown. Our study was designed to investigate the independent role of aortic root GP activity in the initiation of AF. METHODS: In 10 Langendorff-perfused canine hearts, the atrial effective refractory period, pulmonary vein effective refractory period, and percentage of AF induced were measured at baseline and during aortic root GP stimulation. RESULTS: Stimulation of the aortic root GP shortened the atrial effective refractory period from 128 ± 10 ms at baseline to 103 ± 15 ms (P < .05) and shortened the pulmonary vein effective refractory period from 139 ± 14 ms to 114 ± 15 ms (P < .05). Furthermore, the percentage of AF induced in the 10 isolated hearts increased from 10% at baseline to 90% during aortic root GP stimulation (P < .05). CONCLUSIONS: In Langendorff-perfused canine hearts, stimulation of the aortic root GP provokes AF in the absence of any extrinsic cardiac nerve activity. The aortic root GP is an important element in the intrinsic neuronal loop that can increase the risk of AF in isolated heart models.

Additional benefit of cryoballoon-based atrial fibrillation ablation beyond pulmonary vein isolation: modification of ganglionated plexi.

AIMS: It has been known that cryoballoon-based pulmonary vein isolation (PVI) is an efficacious and a safe therapeutic option to eliminate triggers of atrial fibrillation (AF). However, the effect of cryoablation on external modifiers of AF-like ganglionated plexi (GP) has never been investigated. In this study, we aimed to investigate whether vagal reactions probably due to GP modification during cryoablation, are associated with success rates during follow-up. METHODS AND RESULTS: A total of 145 patients (age: 54.5 ± 10.1, 52.4% males and 80.7% paroxysmal AF) who were symptomatic despite treatment with ≥ 1 antiarrhythmic drug underwent PVI with cryoballoon. Occurrences of intraprocedural vagal reactions were recorded in all patients. Intraprocedural vagal reaction was observed in 59 patients (40.7%). Vagal reaction characterized by bradycardia and hypotension was more common in patients free of AF recurrence as was the requirement of atropine administration or temporary pacing (46.2 vs. 15.4%, P = 0.004 and 38.7 vs. 7.7%, P = 0.002, respectively). At a median 17 (4-27) months follow-up, AF recurrence was observed in 26 (17.9%) patients. Multivariate Cox regression analysis showed that non-paroxysmal AF, left atrial diameter, and early recurrence significantly increased AF recurrence; however, requirement of atropine administration or temporary pacing (hazard ratio: 0.064; 95% confidence interval: 0.008-0.48, P = 0.008) decreased AF recurrence. CONCLUSION: Our findings indicate that vagal reactions during cryoablation, as a surrogate marker of cardiac ANS modification, decrease AF recurrence in a subgroup of patients with paroxysmal and persistent AF. This finding may be attributed to the concomitant ablation of GP during antral PVI.

Stand alone surgical ablation for atrial fibrillation.

BACKGROUND: Trials to maintain sinus rhythm in patients with atrial fibrillation (AF) and refractory symptoms have been complicated by lack of success or intolerance of medications. Experience with minimally invasive AF surgery is relatively new, and early results have been promising. However, the study populations and techniques were heterogeneous, and the follow-up periods were short in many series. METHODS: We present a single center experience through a retrospective review of medical records of patients who had minimally invasive AF surgery. RESULTS: The surgical techniques addressed several possible mechanisms of AF and causes of recurrence, including pulmonary vein isolation, underlying substrates modification, ligament of Marshall interruption, ganglion plexus ablation, and left atrial appendage exclusion. Thirty-three cases were identified. The mean duration of follow-up was 23.2 months, and 58.6% were maintained in a sinus rhythm and were off antiarrhythmic drugs at the end of the follow-up period. Cases with persistent AF had a lower success rate. CONCLUSION: Results with minimally invasive surgery are suboptimal at two years of follow-up, particularly for patients with persistent AF.

Epicardial confirmation of conduction block during thoracoscopic surgery for atrial fibrillation--a hybrid surgical-electrophysiological approach.

BACKGROUND: Totally thoracoscopic epicardial pulmonary vein ablation is an emerging treatment of atrial fibrillation (AF). A hybrid surgical-electrophysiological procedure with periprocedural confirmation of conduction block might reduce recurrences of AF or atrial tachycardia and improve surgical success. METHODS AND RESULTS: We report our joint surgical-electrophysiological approach for confirmation of conduction block across pulmonary vein ablation lines and those compartmentalizing the left atrium during totally thoracoscopic surgery. A diagnostic electrophysiology (EP) catheter positioned under the left atrium is used as reference and a custom-made multi-electrode for recording. Determination of conduction block across the pulmonary vein (PV) ablation lines requires measurement of activation time differences of milliseconds. Second, a stable reference electrogram to which to relate local activation time is required. Third, the recording electrode terminals and the inter-electrode distance should be small to prevent recording of far field activity and to allow recording of very small electrograms. We confirm entry and exit block and determine conduction block across linear ablation lines with differential pacing. CONCLUSION: A joint surgical-electrophysiological protocol for confirmation of conduction block across PV isolation lines and left atrial ablation lines is feasible and might prevent recurrences and further improve the success of minimally invasive surgery for AF.

Dormant pulmonary vein conduction induced by adenosine in patients with atrial fibrillation who underwent catheter ablation.

BACKGROUND: intravenous administration of adenosine triphosphate (ATP) is used to induce transient pulmonary vein (PV) reconduction (dormant PV conduction) following PV isolation. This study investigated the detailed characteristics of dormant PV conduction in patients with atrial fibrillation (AF) who underwent catheter ablation. METHODS: two hundred sixty consecutive patients (235 men; mean age, 54 ± 10 years) who underwent catheter ablation of their AF were included in this study. ATP was injected following PV isolation to induce dormant PV conduction, which was then eliminated by radiofrequency application. RESULTS: dormant PV conduction was induced by ATP in 60.4% (157/260) of the patients and in 25.3% (258/1,021) of the isolated PVs. This transient PV reconduction was more frequently observed in the left superior PV in comparison with other PVs (P < .0001). There was no significant difference in the prevalence of the dormant PV conduction among patients with paroxysmal AF, persistent AF, and long-lasting AF (62%, 66%, and 48%, respectively; P = .13). During the follow-up period, repeat AF ablation was performed in 70 patients with recurrent AF. The dormant PV conduction was less frequently induced in the repeat procedure than in the initial procedure (60.4% vs 31.4%, P < .0001). CONCLUSIONS: dormant PV conduction was evenly induced among AF types. The repeat PV isolation led to the decrease in incidence of the ATP-induced acute transient pharmacological PV reconduction.

Histopathological substrate for chronic atrial fibrillation in humans.

BACKGROUND: There is a lack of understanding of the substrate for microreentrant circuits and triggered activity of the pulmonary vein (PV) muscle sleeves and atria in patients with atrial fibrillation (AF). OBJECTIVE: This study sought to examine the histological substrate of patients with chronic AF. METHODS: We stained 23 biopsies taken from the PV-left atrium (LA) junction and right atrial appendage from 5 chronic AF patients and 3 sinus rhythm (SR) patients undergoing mitral valve surgery using periodic acid-Schiff (PAS) test, and antibodies to hyperpolarization-activated cyclic nucleotide-gated potassium channel 4 (HCN4), CD117/c-kit, myoglobin, tyrosine hydroxylase (TH), growth-associated protein 43, cholineacetyltransferase, and synaptophysin, as well as trichrome. RESULTS: As opposed to being clustered together in the subendocardial layer in SR patients, PAS-positive cells were separated from each other by inflammatory infiltrate and collagen fibers in AF patients. These cells stained positively for HCN4 and myoglobin, indicating they were cardiomyocytes that might have a potential pacemaking function, but different from CD117/c-kit-positive interstitial Cajal-like cells (ICLC). In AF patients, the intercellular space was occupied by a lymphomononuclear infiltrate (100% vs 33% in SR patients, P = .002), and a greater amount of interstitial fibrosis (37% +/- 5.6% vs 7.4% +/- 2.8%, P = .009). Nerve densities did not differ between AF and SR patients. However, the density of sympathetic nerve twigs in AF patients was significantly greater as compared to the others nerves (P = .03). CONCLUSION: HCN4-/PAS-positive cardiomyocytes and CD117/c-kit-positive ICLC scattered among abundant inflammatory infiltrate, fibrous tissue, and sympathetic nerve structures in the atria and at the PV-LA junctions might be a substrate for the maintenance of chronic AF.

Current strategies in the management of atrial fibrillation.

Treatment of atrial fibrillation (AF) has been undergoing significant changes recently. This is due partly to different mechanisms proposed for persistent and permanent AF and partly due to the introduction of energy-based techniques, providing less invasive procedures. This article aims to review the mechanisms of AF leading to the changes in clinical practice and to review the results of surgery, energy-based, and percutaneous techniques. It is difficult to compare and contrast the results of reported series in the literature due to different definitions of AF; freedom from and recurrence of it. Furthermore, in most series it is difficult to distinguish results of surgery for lone AF and AF associated with valvular heart disease and coronary artery disease.

A prospective multicenter trial of bipolar radiofrequency ablation for atrial fibrillation: early results.

BACKGROUND: The Cox-Maze III remains the gold standard for the surgical treatment of atrial fibrillation. However, the "cut-and-sew" technique is time consuming and technically challenging. The pulmonary veins are the source of ectopy in the majority of patients with atrial fibrillation. The safety and efficacy of bipolar radiofrequency to electrically isolate the pulmonary veins was evaluated in a prospective multi-center trial. METHODS: Beginning in January 2002, 30 patients at three medical centers underwent pulmonary vein isolation using bipolar radiofrequency and were followed for 6 months. Twenty-four of the patients also underwent a modified Cox-Maze III. Electrical isolation of the pulmonary veins was confirmed with intraoperative pacing. Pulmonary vein patency was assessed by magnetic resonance imaging or three-dimensional computed tomography in 15 patients at 1 month. RESULTS: Mean age was 60.9 +/- 11.7 years. Nineteen patients had paroxysmal atrial fibrillation. All pulmonary veins were isolated in every patient. The left pulmonary veins underwent 3.0 +/- 1.4 applications for a total of 26.4 +/- 10.5 seconds. The right pulmonary veins underwent 2.8 +/- 1.1 applications for a total of 26.3 +/- 12.6 seconds. There was no operative mortality. At 1 month, imaging revealed no evidence of pulmonary vein stenosis. At 6 months, 96% of patients were in normal sinus rhythm. CONCLUSIONS: The use of bipolar radiofrequency for electrical isolation of pulmonary veins and to replace other Cox-Maze III incisions is safe and effective at controlling atrial fibrillation. This emerging technology may shorten and simplify the surgical management of atrial fibrillation.

Functional study on nitroxidergic nerve in isolated dog pulmonary arteries and veins.

In dog pulmonary arterial and venous strips without endothelium under treatment with prazosin, nicotine induced relaxation that was abolished by N(G)-nitro-L-arginine, hexamethonium and methylene blue. L-Arginine antagonized the N(G)-nitro-L-arginine action. Neurogenic relaxations tended to be more evident in the vein. Nitric oxide (NO)-induced relaxations were greater in the veins than in the arteries. Concentrations of NO to induce the same magnitude of relaxation as that to nicotine were higher in the arteries. In conclusion, dog pulmonary arteries and veins are innervated by nitroxidergic (nitrergic) nerves, and NO is released by nerve stimulation with nicotine in a larger amount in the artery than the vein.

Validation of a left atrial lesion pattern for intraoperative ablation of atrial fibrillation.

BACKGROUND: Evidence that atrial fibrillation may begin in early stages from triggers or reentry circuits primarily in the left atrium suggests that the entire Maze 3 lesion pattern may be unnecessary. In the present study we describe a new left atrial lesion pattern for intraoperative linear ablation of chronic atrial fibrillation. METHODS: Endocardial radiofrequency ablation was performed on 12 dogs with chronic atrial fibrillation. Lesions to isolate pulmonary veins in pairs, the left atrial appendage, and connecting lesions between these structures were administered in a randomized approach. RESULTS: Twelve dogs were in chronic atrial fibrillation for 31 +/- 21 days before ablation. Atrial fibrillation was successfully ablated and rendered noninducible in all 12 dogs. All treatment failures observed with less than the full lesion pattern became a success when the remaining lesions were given. CONCLUSIONS: Atrial fibrillation ablation using this left atrial lesion pattern is highly successful in this model. This approach may have significant utility as a concomitant procedure for patients with atrial fibrillation undergoing mitral valve procedures.