The maze procedure for cure of atrial fibrillation

Repeat ablation strategy for recurrent persistent atrial fibrillation: A propensity-matched score comparison between "2C3L" and "extensive ablation" approach

BACKGROUND

Debates exist in the repeat ablation strategy for patients with recurrence presenting as persistent atrial fibrillation (AF) after initial persistent AF ablation.

OBJECTIVE

To compare the outcome between the "2C3L" and "extensive ablation" approach in patients undergoing repeat procedures for recurrent persistent AF.

METHODS

Propensity-score matching was performed in 196 patients with AF recurrence undergoing repeat ablation, and 79 patients treated with "2C3L" strategy were matched to 79 patients treated with "extensive ablation" strategy. The "2C3L" approach included pulmonary vein isolation, mitral isthmus, left atrial roof, and cavotricuspid isthmus ablation, while the "extensive ablation" strategy included extensive ablation of a variety of other targets aiming to terminate the AF. The primary outcome was freedom from any atrial tachyarrhythmia after 24-h ambulatory monitoring follow-up for 12 months.

RESULTS

No statistically significant difference was found between the primary outcome between the "2C3L" and the "extensive ablation" group [70.9% vs. 69.6%, p = .862; 95% confidence interval (CI) -12.8 to 15.3], although the "extensive ablation" group had a significantly high proportion of AF termination (19.0% for "2C3L" vs. 41.8% for "extensive ablation" group, p = .002; 95% CI 8.5-35.9). And AF termination was not related to the primary outcome in multifactorial regression. At 40 ± 22 months after the repeat procedure, the primary outcome was also comparable (57.0 % for "2C3L" vs. 48.1% for "extensive ablation" group, p = .265; 95% CI -6.6 to 23.7).

CONCLUSION

The outcome between the "2C3L" and "extensive ablation" approaches was comparable in patients undergoing repeat procedures for recurrent persistent AF.

The Same is Not the Same: Device Effect during Bipolar Radiofrequency Ablation of Atrial Fibrillation

BACKGROUND

Different ablation devices deliver the same type of energy but use individual control mechanisms to estimate efficacy. We compared patient outcome after the application of radiofrequency ablation systems, using temperature- or resistance-control in paroxysmal and persistent atrial fibrillation (AF).

METHODS

This is an unselected all-comers study. Patients underwent standardized left atrial (paroxysmal atrial fibrillation, [PAF] n = 31) or biatrial ablation (persistent atrial fibrillation [persAF] n = 61) with bipolar RF from October 2010 to June 2013. Patients with left atrial dilatation (up to 57 mm), reduced left ventricular (LV) function, and elderly were included. We used resistance-controlled (RC) or temperature-controlled (TC) devices. We amputated atrial appendices and checked intraoperatively for completeness of pulmonary vein exit block. All patients received implantable loop recorders. Follow-up interval was every 6 months. Antiarrhythmic medical treatment endured up to month 6.

RESULTS

We reached 100% freedom from atrial fibrillation (FAF) in PAF. In perAF 19% of the RC but 82% of the TC patients reached FAF (12 months; p < 0.05). TC patients exhibited higher creatine kinase-muscle/brain (CK-MB) peak values. In persAF, CK-MB-levels correlated to FAF. No and no mortality (30 days) was evident. Twelve-month mortality did not correlate to AF type, AF duration, LV dimension, or function and age. Prolonged need of oral anticoagulants was 90.1% (RC) and 4.5% (TC).

CONCLUSION

In patients with persAF undergoing RF ablation, TC reached higher FAF than RC. Medical devices are not "the same" regarding effectiveness even if used according to manufacturer's instructions. Thus, putative application of "the same" energy is not always "the same" efficacy.

Assessment Of Sinoatrial Node Function In Patients With Persistent And Long-Standing Persistent Forms Of Atrial Fibrillation After Maze III Procedure Combined With Mitral Valve operation

RESEARCH OBJECTIVE

Assessment of sinoatrial node function after Maze III procedure combined with a mitral valve operation.

METHODS

100 patients were included in the research with persistent and long-standing persistent forms of atrial fibrillation (AF) and need of operative treatment concerning valve disease. The following preoperative preparation methods were executed to all patients: Electrocardiogram in 12 standard assignments;Two-dimensional echocardiographic with assessment of systolic and diastolic functions of the left ventricle, size of the left atrium and grade of valve disease;Transesophageal echocardiography for exclusion of blood clots in the left atrium and left atrial appendage;Coronary angiography for exclusion of coronary heart disease;Computer tomography for examination of cardiac chambers and anatomic characteristics of pulmonary veins. Electric cardioversion in X-ray operating room conditions was performed on all patients. After successful restoration of sinus rhythm, electrophysiological examination (EP) of heart was carried out. Then, on the first or second day after EP study, Maze III procedure combined with a mitral valve operation was performed.

RESULTS

Following the results of Maze III procedure combined with correction of valve disease, disposal of AF was observed in 95% of patients. 46% of patients had stable sinus rhythm to the moment of discharge from the hospital. 24% of patients had atrial rhythm with the maximum heart rate of 80-110 bpm (according to results of 24-hour Holter monitoring). For 25% of patients, it was necessary to implant a pacemaker. According to results of EP study, 13% of these patients suffered from sick sinus syndrome before operation. For 9% of the remaining 12% of patients, the indications for pacemaker implantation were atrioventricular nodal rhythm with low heart rate and pauses more than 3 sec long. For 1% of patients the indication was second degree AV block (type 2) and second degree SA block (type 2); for 1% the indication was complete heart block, and for 1% it was atrial rhythm and pauses more than 3 sec long. 13% of patients with an atrial rhythm and normal heart rate developed typical atrial flutter (AFL) in the early postoperative period. For all of them the RF catheter ablation with linear ablation of the right atrial isthmus and creation of isthmus block was effective, and further recurrence of AFL was not observed.

CONCLUSIONS

In the early postoperative period Maze III procedure combined with a mitral valve operation proved to be an effective surgical technique of treatment of persistent and long-standing persistent forms of AF. Only 12% of patients had dysfunction of sinus node work due to iatrogenesis.

2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design

This is a report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation, developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology and the European Cardiac Arrhythmia Society (ECAS), and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). This is endorsed by the governing bodies of the ACC Foundation, the AHA, the ECAS, the EHRA, the STS, the APHRS, and the HRS.

Radiofrequency ablation of cardiac arrhythmias: past, present and future

The treatment of cardiac arrhythmias has been revolutionized by the ability to definitively treat many patients with radiofrequency catheter ablation, rather than requiring lifelong medication. This review covers the history of how this has developed and the methods used currently and explores what the future holds for this rapidly evolving branch of Cardiology.

The efficacy of intraoperative atrial radiofrequency ablation for atrial fibrillation during concomitant cardiac surgery-the Surgical Atrial Fibrillation Suppression (SAFS) Study

INTRODUCTION

Studies assessing radiofrequency ablation (RFA) for atrial fibrillation (AF) performed at the time of concomitant cardiac surgery have reported high success rates. The efficacy of this treatment has primarily been determined by a single electrocardiogram (ECG) or 24-h Holter monitor at follow-up. We sought to assess the true efficacy of this procedure using prolonged cardiac rhythm monitoring.

METHODS

One hundred patients with paroxysmal (n = 47) and persistent AF (n = 53) requiring cardiac surgery were enrolled. Patients were clinically reviewed 6 weeks post-operatively and were monitored with 7-day Holter with full disclosure, 6 months post-surgery. A cohort of 50 patients also underwent 7 day Holter monitoring preoperatively. AF recurrence was defined as >30 s of AF.

RESULTS

At 6 months, 75% of patients were in sinus rhythm according to a single ECG. However, only 62% of patients were free from AF on 7-day Holter; all AF episodes in these patients were asymptomatic. The procedure resulted in a significant decrease in AF burden from 56.2% at baseline to 27.5% at 6 months follow-up, (p < 0.001). Predictors of AF recurrence were (1) pre-operative AF duration; (2) persistent compared with paroxysmal AF; (3) increasing left atrial diameter and (4) requirement for mitral valve surgery.

CONCLUSIONS

Surgical RFA for the treatment of AF, during concomitant cardiac surgery, is a successful procedure and significantly reduces AF burden. However, 13% of patients have asymptomatic AF episodes only identified with continuous monitoring. This has important implications for post-operative anti-arrhythmic and anticoagulant management and for the definition of surgical AF ablation success.

Pharmacologic targets for atrial fibrillation

Despite advances in treatment, atrial fibrillation (AF) remains the most common arrhythmia in humans. Antiarrhythmic drug therapy continues to be a cornerstone of AF treatment, even in light of emerging non-pharmacologic therapies. Conventional antiarrhythmic drugs target cardiac ion channels and are often associated with modest AF suppression and the risk of ventricular proarrhythmia. Ongoing drug development has focused on targeting atrial-specific ion channels as well as novel non-ionic targets. Targeting non-ionic mechanisms may also provide new drugs directed towards the underlying mechanisms responsible for AF and possibly greater antiarrhythmic potency. Agents that act against these new targets may offer improved safety and efficacy in AF treatment.

Adjunctive atrial fibrillation therapy with off-pump coronary artery bypass grafting: standard of care?

OBJECTIVES

: To validate the safety and applicability of a previously unreported innovative technique: bipolar epicardial radiofrequency pulmonary vein ablation for the treatment of atrial fibrillation (AF) in conjunction with off-pump coronary artery bypass surgery.

METHODS

: After the completion of off-pump coronary artery bypass grafting (OPCAB) via sternotomy, patients underwent epicardial pulmonary vein ablation using a bipolar radiofrequency clamp placed on the left atrial cuff. The left atrial appendage was removed or excluded in all patients.

RESULTS

: Fifteen patients (aged 59-81 years) were treated and reviewed. An average of 2.8 ± 1 grafts were performed per patient; all patients received left internal mammary artery grafts. All sets of pulmonary veins were encircled successfully and ablated. Four patients had additional lesions placed. No patient had pulmonary vein injury. There were no reoperations for bleeding and no mortality. Preoperatively, AF was continuous in 4 patients and intermittent in 11; 10 patients were taking Coumadin preoperatively and 11 were taking antiarrhythmic drugs (AAD). At the follow-up evaluation (7.6 ± 4.4 months; range 1-16 months), 12 patients (80%) are in sinus rhythm (100% in the intermittent AF group, 25% in the continuous AF group); Coumadin has been discontinued in 5 of 10 patients (50% reduction) and AAD have been discontinued in 7 of 11 patients (74% reduction).

CONCLUSIONS

: Bipolar radiofrequency epicardial pulmonary vein ablation can be safely and reproducibly used for the treatment of AF in conjunction with OPCAB. Patients with intermittent AF should be strongly considered for adjunctive treatment at the time of OPCAB.

Ablation of Atrial Fibrillation

Due in large part to the growing dissatisfaction with traditional pharmacologic approaches to atrial fibrillation (AF) management, and fueled by both the fruits of basic and clinical investigation into the nature of AF initiation and maintenance and the explosive development in catheter-based technologies, AF ablation has matured from a purely investigational technique to a viable--and often preferred--strategy for treating patients suffering from this arrhythmia. Future insights and developments will help us refine our treatment strategies, making AF ablation safer, faster, and more effective. As the prevalence of AF in the general population continues to expand, the goal of optimizing our approach to AF becomes ever more important--and more pressing.

A new minimally invasive heart surgery instrument for atrial fibrillation treatment: firstin vitro and animal tests

BACKGROUND

The paper presents a new robotic system for beating heart surgery. The final goal of this project is to develop a tele-operated system for the thoracoscopic treatment of patients with atrial fibrillation. The system consists of a robot that moves an innovative end-effector used to perform lines as in the Cox-Maze technique.

METHODS

The device is an electrode mesh that is introduced in the thorax through a trocar and is deployed inside the left atrium, where it can create selective ablation lines at any atrial region, using radio frequency. The current version of the umbrella has 22 electrodes. Using visual feedback from an ultrasound based navigation system, the surgeon can choose which electrodes on the mesh to activate. Once the umbrella is in contact with the endocardium of the left atrium, at the expected position, the surgeon activates the chosen electrodes sequentially. The umbrella can then be moved to another position.

RESULTS

In vitro and in vivo animal tests have been carried out in order to test and improve the instrument, the robotic system and the operative procedure.

CONCLUSIONS

The performed trials proved the ability of the system to treat atrial fibrillation. More in vivo tests are currently being performed to make the robot and its device ready for clinical use.

Surgical Ablation of Atrial Fibrillation

Surgical ablation of atrial fibrillation (AF) is the most effective means of curing this arrhythmia, with the classic Maze procedure eliminating AF in more than 90% of patients. A complex but safe operation, the Maze procedure has been applied by relatively few surgeons. However, recent advances in the understanding of the pathogenesis of AF and development of new ablation technologies enable surgeons to perform pulmonary vein ablation, create linear left atrial lesions, and remove the left atrial appendage rapidly and safely. Lesions are created under direct vision, minimizing the risk of damage to the pulmonary veins and adjacent mediastinal structures. Most surgical ablation procedures have been performed in conjunction with mitral valve surgery, the combination of mitral valve repair and cure of AF enabling patients to avoid lifelong anticoagulation. Recently developed surgical instrumentation now enables thoracoscopic and keyhole approaches, facilitating extension of epicardial AF ablation and excision of the left atrial appendage to patients with isolated AF and no other indication for cardiac surgery.

Warfarin for atrial fibrillation: the end of an era?

BACKGROUND

Warfarin has been in routine clinical use for more than 50 years; however, it was not proven to be of benefit in both primary and secondary prevention of stroke for patients with non-valvular atrial fibrillation (AF) until about a decade ago. Despite its efficacy in reducing the risk of stroke in patients with AF by about 60%, with an absolute reduction of about 3% per year, there have always been barriers to its use. These barriers have included the need for monitoring the degree of anticoagulation with blood tests to measure the international normalised ratio, frequent dose adjustments to maintain this ratio within quite a narrow therapeutic range, and the risk of bleeding should the upper limits of this range be exceeded. Aspirin has also been used but is less effective.

RECENT DEVELOPMENTS

New oral drugs are being tested; these may be as effective at reducing stroke risk as warfarin in patients with AF. Direct thrombin inhibitors such as ximelagatran are not inferior to warfarin and, based on results from the SPORTIF III and V trials, are perhaps safer, with no need for long-term monitoring and dose adjustment. However, the side-effect of raised amounts of the liver enzyme alanine amino-transferase in 6% of patients needs to be resolved. In the ACTIVE trial, the efficacy of a combination of antiplatelet drugs (aspirin plus clopidogrel) is being tested against dose-adjusted warfarin; and in AMADEUS, the factor-Xa inhibitor and pentasaccharide idraparinux is being assessed in a similar way. Several surgical procedures and devices are also being developed to control AF rhythm and prevent stroke. WHERE NEXT?: The place of these new drugs in the management of AF needs to be established. In the short term, it seems that ximelagatran will replace warfarin in patients for whom there is evidence of a favourable risk-to-benefit ratio. The SPORTIF population consists of patients with AF plus at least one risk factor. More information about the effect of raised liver enzymes will probably not be available until phase IV studies are completed. Combination antiplatelet drugs need to be tested further--perhaps even triple therapy with aspirin, clopidogrel, and dipyridamole--if the results of ACTIVE are encouraging. The place of surgical procedures and devices to control rhythm and prevent stroke is unclear. Whatever happens, there is a high probability that the days of warfarin are numbered.

Advances in the surgical treatment of atrial fibrillation

There has been a resurgence in the surgical treatment of AF. Although the Maze procedure is extremely effective at curing AF, new surgical approaches are far simpler and include pulmonary vein isolation, left atrial lesions, and excision of the left atrial appendage. Currently applied as an adjunct to other cardiac operations, these new approaches are being modified for thoracoscopic, minimally invasive, epicardial AF ablation. This minimally invasive procedure will enable rapid and effective cure of AF in large numbers of patients.

Evolution of non-pharmacological curative therapy for atrial fibrillation. Where do we stand today?

The present review aims at giving a comprehensive synthesis regarding not only the epidemiological aspects but also the evolution, over the last decades, of the curative surgical and catheter-based ablative treatments for atrial fibrillation (AF), with particular emphasis on the experience of Milan working group which has always been committed to the on-going and fascinating therapeutic challenges inherent in this type of cardiac arrhythmia. After discussing the surgical treatment of AF we report the rationale basis of current pulmonary vein (PV) ablation techniques. In particular, we report on circumferential PV ablation, an intellectually appealing strategy, aimed at creation of RF lesions around each PV ostia using a non-fluoroscopic electro-geometric mapping system to reconstruct the anatomy of venous-atrial junction, allowing to tailor number and size of lesions to the complex morphology of the PV-LA junction in each patient. This purely anatomic approach not only disconnects PVs (as demonstrated by elimination of PV ostial potentials and absence of discrete electrical activity inside the lesion during pacing outside the ablation line), but also, like surgery, reduces the "electrically active" atrial tissue, involving substantial parts of the posterior LA wall, with a profound atrial electroanatomic remodeling, as expressed by voltage abatement (<0.1 mV) inside and around the encircled areas.

Atrial fibrillation: current surgical options and their assessment

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with morbidity and mortality. Traditional surgical treatment of AF is the Cox-Maze III procedure, a complicated operation. New surgical approaches include alternate energy sources (radiofrequency, microwave, cryothermy) and simplified left atrial lesion sets. These operations cure AF in 70% to 80% of patients. This review describes contemporary and emerging surgical approaches to AF, synthesizes results of these operations, and proposes new standards for reporting results of AF treatment.

Catheter ablation for cardiac arrhythmias

The safety and efficacy of catheter ablation for treatment of most types of cardiac arrhythmias are well established. These arrhythmias and arrhythmia substrates include AVNRT, accessory pathways, focal atrial tachycardia, atrial flutter, idiopathic ventricular tachycardia, and bundle-branch re-entry. Catheter ablation is considered as an alternative to pharmacologic therapy in the treatment of these cardiac arrhythmias.

Ablation of atrial fibrillation: a procedure come of age?

Various approaches for catheter ablation of focal initiators of atrial fibrillation or the substrate for maintaining atrial fibrillation have evolved over the past 5 years. Despite these advances, there are still a large number of unresolved issues regarding the efficacy and safety of these procedures as well as optimal patient selection for the different approaches. These uncertainties raise questions about the applicability at the present time of atrial fibrillation as front-line therapy within the community.

The maze III procedure for atrial fibrillation: should the indications be expanded?

BACKGROUND

We favor the maze III procedure over nonsurgical treatments for atrial fibrillation and have advocated addition of the maze in symptomatic patients with other compelling indications for cardiac surgery.

METHODS

Characteristics and perioperative outcomes of our 76 cumulative maze recipients between 1993 to 1998 were reviewed. The original maze III technique was employed without modification.

RESULTS

Isolated maze III was performed in 19 patients (25%) and combined with other procedures in 57 patients (75%), 49 of these involving one or more valves. Patients having combined procedures were taking fewer antiarrhythmics (p < 0.0001), but were older (p < 0.01), more often female (p < 0.05), and more often had chronic atrial fibrillation (p < 0.01) compared with isolated maze III recipients. The mean duration of aortic clamping and cardiopulmonary bypass for isolated maze was 69 +/- 11 and 145 +/- 22 minutes, and for combined valve procedures it was 122 +/- 38 and 205 +/- 47 minutes. There was no operative mortality. Complications occurred in 15 patients (19.7%). At 3 months atrial fibrillation was cured in 73 of 75 patients (97.3%). Sick sinus syndrome required pacemaker implantation in 3 patients (4.0%).

CONCLUSIONS

The maze III can be performed alone or as a combined procedure with equivalent success, and technical modifications may be unnecessary. A lower threshold for its expanded use in symptomatic patients with atrial fibrillation who require isolated or combined operations is appropriate.

Prospective comparison of lesions created using a multipolar microcatheter ablation system with those created using a pullback approach with standard radiofrequency ablation in the canine atrium

The aim of this study was to compare the lesions created using a multipolar microcatheter (MICRO) ablation system in the right canine atrium to a pullback approach with a standard radiofrequency (STND RF) ablation and to determine the value of electrogram amplitude and pacing threshold in predicting transmurality of lesions. Ten dogs underwent right atrial ablation using a MICRO (6 dogs) or STND RF (4 dogs) ablation system in each animal. Attempts were made to create linear RF lesions at four predetermined atrial sites. RF energy was delivered for 60 seconds using closed-loop, temperature control to achieve a target temperature of 60 degrees C for STND RF and 50 degrees C for MICRO. Unipolar atrial electrogram amplitude and atrial pacing threshold were obtained before and after ablation. Pathological analysis was determined at 4 weeks after ablation. Lesions created with MICRO were narrower, more likely to be continuous, and more likely to be anchored to an anatomic structure than those lesions which were created using a STND RF. No difference was observed in overall lesion length or in the proportion of lesions that were transmural over at least 50% of their length. Of lesions created using MICRO, a significant relation was observed between transmurality of lesion and unipolar electrogram amplitude as well as pacing threshold. Further studies are needed to determine if this type of ablation technique and parameters during ablation may facilitate a successful catheter-based MAZE procedure.

The Cox-Maze procedure: the Cleveland Clinic experience

The Cox-Maze procedure was designed to address the consequences of atrial fibrillation, tachycardia, hemodynamic impairment, and thromboembolism. From 1991 until June 1999, 100 patients underwent the Maze operation at the Cleveland Clinic Foundation. The group included 72 men with a mean age of 58 +/- 11 years (range, 23 to 78 years). Initially, the Maze-I procedure was performed primarily for patients with lone atrial fibrillation. However, since 1995, the Maze-III procedure has been performed exclusively, and it is typically combined with mitral valve repair. Twenty-three patients had only a Maze procedure, 60 patients had the Maze procedure/mitral valve repair, 10 patients had Maze procedure/coronary artery bypass, 6 had Maze procedure/mitral valve replacement, and 1 had Maze procedure/atrial septal defect repair. Chronic atrial fibrillation was present in 78% of patients for a mean of 8 +/- 9 years. There was a 1% perioperative mortality and 5% late mortality rate. Median hospital stay was 9 +/- 5 days. Six patients required new early permanent pacemaker insertion. With a mean follow-up of 3 years, 90.4% of patients are in sinus rhythm (or atrial pacing). Preoperative symptoms were reduced: 24% had preoperative syncope; none had syncope in follow-up; 14% of patients preoperatively had cerebral or systemic emboli; and there were no perioperative or late embolic events. The Maze procedure effectively addressed the major complications of atrial fibrillation and was associated with low perioperative and late morbidity rates.

The Maze procedure: the LDS Hospital experience

At our center we have encouraged consideration of the Maze procedure over noncurative therapies for atrial fibrillation, particularly in patients who have other indications for cardiac surgical intervention. As a result, 78 of the 99 Maze procedures we have performed since 1993 have involved combined procedures. These combined operations included procedures on 1 or more valves in 69 of 78 patients (88%). The unmodified "cut-and-sew" Maze-III technique was used in all patients. There has been no operative mortality, and the median postoperative stay has been 7 days. Cure of atrial fibrillation has been observed in 97% of patients, and pacemaker implantation was required for sick sinus syndrome in 6%. Our results favor broader use of the Maze procedure for symptomatic atrial fibrillation and support use of the original Maze-III technique as the procedure of choice.

A new system for catheter ablation of atrial fibrillation

Increased attention is now being focused on developing new technologies to cure atrial fibrillation using catheter ablation techniques. The performance of a MAZE-type procedure using standard catheter ablation technologies is arduous and is associated with an unacceptable risk of complications. The Guidant Heart Rhythm Technologies Linear Ablation System was developed to create long transmural linear lesions. Unique features of this system include the availability of different preshaped multi-electrode steerable ablation catheters, the use of phased radiofrequency (RF) energy, and the control of RF output by varying the duty cycle. A prospective multicenter clinical trial to evaluate the safety and efficacy of a right atrial ablation procedure using this technology to treat atrial fibrillation is currently underway. To date, 15 patients have been enrolled and the procedure was acutely effective in 14 of 15 patients with no complications. Atrial fibrillation has recurred during short-term follow-up in 12 of 15 patients, a not surprising result, because this initial phase of testing involved only right-sided ablation. The early results of the phase I clinical trial confirm the findings of others that successful ablation of chronic atrial fibrillation is likely to require a left atrial approach. This clinical trial, as well as others that are currently underway, will be invaluable in the continuing development of catheter ablation of atrial fibrillation and, ultimately, in determining if the routine use of this therapeutic tool can become a reality.