Atrial size and transport function after the Maze III procedure for paroxysmal atrial fibrillation

A Modified Maze Versus Cut-and-Sew Maze for Long-Standing Persistent Atrial Fibrillation Concomitant with Mitral Valve Surgery: A Propensity Score-Matched Cohort Study

BACKGROUND

The cut-and-sew maze (CSM) procedure has an excellent efficacy for the elimination of long-standing persistent atrial fibrillation (AF) concomitant with mitral valve surgery. Because of the complexity and prolongation of cardiopulmonary bypass, CSM has not been widely used. The aim of this study was to examine a modified maze procedure that preserves the "cut-and-sew" procedure in the left atrium and uses cryoablation in the right atrium along with cavotricuspid isthmus.

METHODS

From December 2013 to December 2018, 229 patients underwent CSM, and 43 underwent the modified maze procedure during mitral valve surgery. Propensity score matching analysis was used to perform selective 1:2 ratio matching of the 43 patients undergoing the modified maze procedure with 86 patients undergoing CSM. Early operative outcomes were analyzed for differences. The absence of AF recurrence without the use of anti-arrhythmic drugs was calculated at 2 years by a generalized linear model analysis.

RESULTS

One (1.1%) early death occurred in the CSM group, and no deaths occurred in the modified maze group (p=0.722). The aortic cross-clamp durations were 76.30±8.86 minutes for the modified maze and 92.38±10.88 for the CSM procedure (p<0.001). There were no late strokes or deaths during the 2-year follow-up. The modified maze group showed similar rates of absence of AF without the use of anti-arrhythmic drugs as the CSM group within the 2 years (p=0.332).

CONCLUSION

This modified maze simplifies the "cut-and-sew" procedure and reduces operating time while retaining the efficacy of CSM.

Left atrial function after epicardial pulmonary vein isolation in patients with atrial fibrillation

Purpose

Epicardial pulmonary vein isolation has become an increasingly used therapy for medically resistant atrial fibrillation. The purpose of the present study was therefore to evaluate if epicardial pulmonary vein isolation combined with ganglionated plexi ablation affects the size and mechanical function of the left atrium, and whether the effects are dependent on the extensiveness of the ablation applications.

Methods

A total of 42 patients underwent an echocardiographic examination prior to and 6 months after a minimal invasive epicardial pulmonary vein isolation procedure for the assessment of the effects on left atrial size and function. In 27 patients, who had sinus rhythm both at baseline and follow-up, was a comparison of atrial size and function possible at these time intervals. Fractional area changes were obtained from the left atrial end-systolic and end-diastolic areas in the apical four-chamber view. Pulsed-Doppler was used to assess the transmitral flow velocities to evaluate mechanical function.

Results

Left atrial size and function at 6-month follow-up had not changed significantly from those at baseline as indicated by left atrial maximal area (17.1 ± 4.6 vs. 18.7 ± 5.3, p = 0.118), minimal area (12.5 ± 3.8 vs. 13.4 ± 4.7, p = 0.248), fractional area change (27.4 ± 8.2 vs. 28.7 ± 10.6, p = 0.670), and E/A ratio (1.49 ± 0.47 vs. 1.54 ± 0.67, p = 0.855).

Conclusions

Radiofrequency ablation for epicardial pulmonary vein isolation combined with ganglionated plexi ablation has no major effects on atrial function or size. A preserved atrial function for those maintaining sinus rhythm may have important implications for thromboembolic risk after surgery, but warrants confirmation in larger trials.

Modified radial v/s biatrial maze for atrial fibrillation in rheumatic valvular heart surgery

BACKGROUND

Atrial fibrillation (AF) is commonest sustained atrial arrhythmia producing high morbidity. Although Cox's Maze III procedure cures AF in majority, reduced atrial transport function (ATF) is a concern. Radial approach with ablation lines radial from sinus node towards atrioventricular annulii and parallel to atrial coronary arteries, has shown better ATF.

METHODS

Single blind open randomized prospective study of 80 patients was undertaken in two groups (40 each) of modified Cox's maze III and modified radial approach, to evaluate conversion to normal sinus rhythm (NSR) and ATF. Patients undergoing surgery for rheumatic valvular heart disease with continuous AF were prospectively randomized. Ablation lines were created with radiofrequency (RF) bipolar coagulation with cryoablation for the isthmal lesions and coronary sinus. Results were compared at 6 months and ATF was evaluated by atrial filling fraction (AFF) and A/E ratio on echocardiography.

RESULTS

The rate of conversion to NSR in both groups was statistically insignificant by Fisher's exact test (p > 0.05). ATF was better in modified radial approach compared to modified Cox's Maze III (A/E compared by unpaired t test:0.52 ± 0.08 v/s 0.36 ± 0.10; p < 0.05. AFF compared using Mann Whitney U test: median AFF for radial group was 23 v/s 20 for biatrial group; p < 0.05).

DISCUSSION

In patients with AF undergoing rheumatic valvular surgery, radiofrequency radial approach is as effective as modified Cox's maze III for conversion to NSR with better atrial transport function.

Quantification of the functional consequences of atrial fibrillation and surgical ablation on the left atrium using cardiac magnetic resonance imaging

OBJECTIVES

The effect of atrial fibrillation (AF) on left atrial (LA) function has not been well defined and has been largely based on limited echocardiographic evaluation. This study examined the effect of AF and a subsequent Cox-Maze IV (CMIV) procedure on atrial function.

METHODS

Cardiac magnetic resonance imaging (cMRI) was performed in 20 healthy volunteers, 8 patients with paroxysmal atrial fibrillation (PAF) and 7 patients with persistent or long-standing persistent atrial fibrillation (LSP AF). Six of the PAF patients underwent surgical ablation with the CMIV procedure and 5 underwent both pre- and postoperative cMRIs. The persistent or LSP AF patients underwent only postoperative cMRIs because all scans were performed with patients in normal sinus rhythm. Volume-time curves throughout the cardiac cycle and regional wall shortening were evaluated using the cine images and compared across groups.

RESULTS

Compared with normal volunteers, patients with PAF had significantly decreased reservoir contribution to left ventricular (LV) filling (P = 0.0010), an increased conduit function contribution (P = 0.04) and preserved booster pump function (P = 0.14). Following the CMIV procedure, significant reductions were noted with respect to reservoir and booster pump function, with corresponding increases in conduit function. These differences were more drastic in patients with persistent/LSP AF. Regional wall motion was significantly reduced by PAF in all wall segments (P < 0.05), but was not further reduced by the CMIV. Despite changes in LA function, LV function was preserved following surgery.

CONCLUSIONS

PAF significantly altered LA function and has a detrimental effect on regional wall motion. Surgical intervention further altered LA function, but the reasons for this are likely multifactorial and not entirely related to the lesion set itself.

The CURE-AF trial: a prospective, multicenter trial of irrigated radiofrequency ablation for the treatment of persistent atrial fibrillation during concomitant cardiac surgery

BACKGROUND

Ablation technology has been introduced to replace the surgical incisions of the Cox-Maze procedure in order to simplify the operation. However, the efficacy of these ablation devices has not been prospectively evaluated.

OBJECTIVE

The purpose of this study was to examine the efficacy and safety of irrigated unipolar and bipolar radiofrequency ablation for the treatment of persistent and long-standing persistent atrial fibrillation (AF) during concomitant cardiac surgical procedures.

METHODS

Between May 2007 and July 2011, 150 consecutive patients were enrolled at 15 U.S. centers. Patients were followed for 6 to 9 months, at which time a 24-hour Holter recording and echocardiogram were obtained. Recurrent AF was defined as any atrial tachyarrhythmia (ATA) lasting over 30 seconds on the Holter monitor. The safety end-point was the percent of patients who suffered a major adverse event within 30 days of surgery. All patients underwent a biatrial Cox-Maze lesion set.

RESULTS

Operative mortality was 4%, and there were 4 (3%) 30-day major adverse events. Overall freedom from ATAs was 66%, with 53% of patients free from ATAs and also off antiarrhythmic drugs at 6 to 9 months. Increased left atrial diameter, shorter total ablation time, and an increasing number of concomitant procedures were associated with recurrent AF (P <.05).

CONCLUSION

Irrigated radiofrequency ablation for treatment of AF during cardiac surgery was associated with a low complication rate. No device-related complications occurred. The Cox-Maze lesion set was effective at restoring sinus rhythm and had higher success rates in patients with smaller left atrial diameters and longer ablation times.

Surgery for Lone Atrial Fibrillation: Present State-of-the-Art

For two decades, the cut-and-sew Cox-Maze III procedure was the gold standard for the surgical treatment of atrial fibrillation (AF), and proved to be effective at curing lone AF and preventing its most dreaded complication, stroke. However, this procedure was not widely adopted due to its complexity and technical difficulty. Over the last 5-10 years, the introduction of new ablation technology has led to the development of the Cox-Maze IV procedure, as well as, more limited lesion sets, with the ultimate goal of performing a minimally-invasive lesion set on the beating heart, without the need for cardiopulmonary bypass. This review summarizes the current state of the art and future directions in the surgical treatment of lone atrial fibrillation. The hope is that as we learn more about the mechanisms of AF and develop preoperative diagnostic technologies capable of precisely locating the areas responsible for AF, it will become possible to tailor specific lesion sets and ablation modalities to individual patients, making the surgical treatment of lone AF available to a larger population of patients.

Atrial Remodeling And Atrial Fibrillation: Mechanistic Interactions And Clinical Implications

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. The prevalence of AF increases dramatically with age and is seen in as high as 9% of individuals by the age of 80 years. In high-risk patients, the thromboembolic stroke risk can be as high as 9% per year and is associated with a 2-fold increase in mortality. Although the pathophysiological mechanism underlying the genesis of AF has been the focus of many studies, it remains only partially understood. Conventional theories focused on the presence of multiple re-entrant circuits originating in the atria that are asynchronous and conducted at various velocities through tissues with various refractory periods. Recently, rapidly firing atrial activity in the muscular sleeves at the pulmonary veins ostia or inside the pulmonary veins have been described as potential mechanism,. AF results from a complex interaction between various initiating triggers and development of abnormal atrial tissue substrate. The development of AF leads to structural and electrical changes in the atria, a process known as remodeling. To have effective surgical or catheter ablation of AF good understanding of the possible mechanism(s) is crucial.Once initiated, AF alters atrial electrical and structural properties that promote its maintenance and recurrence. The role of atrial remodeling (AR) in the development and maintenance of AF has been the subject of many animal and human studies over the past 10-15 years. This review will discuss the mechanisms of AR, the structural, electrophysiologic, and neurohormonal changes associated with AR and it is role in initiating and maintaining AF. We will also discuss briefly the role of inflammation in AR and AF initiation and maintenance, as well as, the possible therapeutic interventions to prevent AR, and hence AF, based on the current understanding of the interaction between AF and AR.

The effects of the Cox maze procedure on atrial function

OBJECTIVE

The effects of the Cox maze procedure on atrial function remain poorly defined. The purpose of this study was to investigate the effects of a modified Cox maze procedure on left and right atrial function in a porcine model.

METHODS

After cardiac magnetic resonance imaging, 6 pigs underwent pericardiotomy (sham group), and 6 pigs underwent a modified Cox maze procedure (maze group) with bipolar radiofrequency ablation. The maze group had preablation and immediate postablation left and right atrial pressure-volume relations measured with conductance catheters. All pigs survived for 30 days. Magnetic resonance imaging was then repeated for both groups, and conductance catheter measurements were repeated for the right atrium in the maze group.

RESULTS

Both groups had significantly higher left atrial volumes postoperatively. Magnetic resonance imaging-derived reservoir and booster pump functional parameters were reduced postoperatively for both groups, but there was no difference in these parameters between the groups. The maze group had significantly higher reduction in the medial and lateral left atrial wall contraction postoperatively. There was no change in immediate left atrial elastance or in the early and 30-day right atrial elastance after the Cox maze procedure. Although the initial left atrial stiffness increased after ablation, right atrial diastolic stiffness did not change initially or at 30 days.

CONCLUSIONS

Performing a pericardiotomy alone had a significant effect on atrial function that can be quantified by means of magnetic resonance imaging. The effects of the Cox maze procedure on left atrial function could only be detected by analyzing segmental wall motion. Understanding the precise physiologic effects of the Cox maze procedure on atrial function will help in developing less-damaging lesion sets for the surgical treatment of atrial fibrillation.

Structural and functional remodeling of the left atrium: clinical and therapeutic implications for atrial fibrillation

Left atrial (LA) structural and functional remodeling reflects a spectrum of pathophysiological changes that have occurred in response to specific stressors. These changes include alterations at the levels of ionic channels, cellular energy balance, neurohormonal expression, inflammatory response, and physiologic adaptations. There is convincing evidence demonstrating an important pathophysiological association between LA remodeling and atrial fibrillation (AF). Measures that will prevent, attenuate, or halt these processes of LA remodeling may have a major public health impact with respect to the epidemic of AF. In this review, we describe the mechanisms involved in LA remodeling and highlight the existing and potential therapeutic options for its reversal, and implications for AF development.

Surgical Treatment of Atrial Fibrillation: A Look into the Future

The surgical treatment of atrial fibrillation began in 1987, when Dr. James Cox introduced the maze procedure. This operation proved to be extremely effective in curing atrial fibrillation and preventing its most dreaded complication, stroke. However, many surgeons found the operation to be too difficult and invasive. Over the last 5 to 10 years, various groups have tried to develop less invasive approaches using a number of different energy sources to create linear lines of ablation to replace the surgical incisions. This has led to a plethora of new operations for this arrhythmia. There is significant confusion in the literature at the present time as to what is the best lesion pattern and what is the best energy source. It is our feeling that a great deal of this confusion is due to our lack of understanding of the mechanisms of atrial fibrillation and the effect of ablation technology on atrial hemodynamics and electrophysiology. Future progress will require a better understanding of this arrhythmia and continued research into the safety and efficacy of ablation devices.

Modification of the Cox-Maze III Procedure Using Bipolar Radiofrequency Ablation

The Cox-Maze III procedure remains the yardstick by which all treatments for atrial fibrillation are measured. This procedure is not widely adopted because of its perceived technical complexity, invasiveness and longer procedural time. Efforts have been made by various investigators to reproduce Dr Cox's results using alternative lesion sets and energy sources. Bipolar radiofrequency (BPRF) ablation avoids the morbidity of cut-and-sew lesions, reduces procedural time and increases the likelihood of transmurality and continuity of lesions created compared to unipolar devices. Initial results are encouraging. We present our surgical technique and early experience using BPRF modification of the Cox-Maze III procedure using the Medtronic Cardioblate BP system.

Off-Pump Epicardial Atrial Fibrillation Surgery Utilizing a Novel Bipolar Radiofrequency System

BACKGROUND

Over the past several years, pulmonary vein isolation for the treatment of atrial fibrillation has gained significant popularity. This study was undertaken to evaluate a novel radiofrequency (RF)-enabled clamp system designed to create transmural lesions epicardially on the beating heart using bipolar RF.

METHODS

A set of differently shaped clamps modified to deliver bipolar RF energy were used to create a series of lesions in a beating heart canine model. The pulmonary veins and atrial appendages of 6 dogs were electrically isolated using bipolar RF energy. The right and left atrial appendages served as controls for the right and left pulmonary veins, respectively. Temperature-controlled RF energy was delivered to maintain a tissue temperature of 80 degrees C for 15 seconds. Electrical isolation was assessed acutely and after 4 weeks by a bipolar pacing protocol.

RESULTS

A total of 24 circumferential lesions were created. By pacing analysis, 100% (24/24) of these lesions were electrically isolated acutely and 95% (19/20) were still isolated 4 weeks later. At 4 weeks, 92% (22/24) of lesions were transmural by histologic analysis, and 96% (23/24) demonstrated endocardial continuity. One animal experienced a fatal cardiac arrhythmia during initiation of the post-survival procedure, prior to electrophysiologic evaluation, accounting for the reduced number of potential electrically isolated lesions.

CONCLUSION

Bipolar RF ablation utilizing a novel bipolar RF clamp device results in electrical isolation and histologic transmurality in an off-pump epicardial model.

Extensive Ablation During Pulmonary Vein Antrum Isolation Has No Adverse Impact on Left Atrial Function: An Echocardiography and Cine Computed Tomography Analysis

BACKGROUND

Although pulmonary vein antrum isolation (PVAI) may cure atrial fibrillation (AF) and improve left atrial (LA) function, the effect of extensive LA ablation on LA function is not well known.

OBJECTIVE

To assess the impact of PVAI on LA function remotely postablation.

METHODS

Consecutive patients undergoing PVAI had either transthoracic (TTE) and transesophageal (TEE) echocardiography (n = 41) or cine EBCT (n = 26) performed preablation and 6 months postablation. Only patients with paroxysmal and persistent, but not permanent, AF were included. Imaging was done in sinus rhythm for all patients. LA diameter (LAD), LA systolic and diastolic areas, and left atrial fractional area change (LFAC) were assessed by TTE. Transmitral (TMF), left atrial appendage (LAA), and pulmonary venous (PVF) Doppler flows were measured by TEE. Peak A on TMF, LAA peak emptying velocity (LAAF), and peak A reversal (AR) on PVF were used as surrogates of LA contractile function. Peak S on PV flow was used as a surrogate of reservoir function. LA areas, volumes, and LA ejection fraction (LAEF) were measured from cine EBCT.

RESULTS

Mean radiofrequency ablation time was 45 +/- 21 minutes. All four PVs were isolated for all patients; there were no cases of PV stenosis. Echocardiography revealed a significant reduction in LAD and LA areas post-PVAI. Both peak A and peak AR were also higher post, while other variables showed strong trends toward improvement. In the subset of patients with persistent AF, post-PVAI improvements were seen in LA size, peak A, and even peak S (P = 0.04). Cine EBCT showed a significant decrease in both LA areas and volumes post-PVAI. There was also a significant improvement in LAEF post-PVAI from 17 +/- 6% to 22 +/- 5% (P = 0.01).

CONCLUSION

Extensive ablation during PVAI does not cause deterioration in LA function, and may cause long-term improvement, especially in patients with higher AF burden.

Effect of left atrial circumferential ablation for atrial fibrillation on left atrial transport function

BACKGROUND

The effects of left atrial (LA) circumferential ablation on LA function in patients with atrial fibrillation (AF) have not been well described.

OBJECTIVES

The purpose of this study was to determine the effect of LA circumferential ablation on LA function.

METHODS

Gated, multiphase, dynamic contrast-enhanced computed tomographic (CT) scans of the chest with three-dimensional reconstructions of the heart were used to calculate the LA ejection fraction (EF) in 36 patients with paroxysmal (n = 27) or chronic (n = 9) AF (mean age 55 +/- 11 years) and in 10 control subjects with no history of AF. Because CT scans had to be acquired during sinus rhythm, a CT scan was available both before and after (mean 5 +/- 1 months) LA circumferential ablation (LACA) in only 10 patients. A single CT scan was acquired in 8 patients before and in 18 patients after LACA ablation. Radiofrequency catheter ablation was performed using an 8-mm-tip catheter to encircle the pulmonary veins, with additional lines along the mitral isthmus and the roof.

RESULTS

In patients with paroxysmal AF, LA EF was lower after than before LACA (21% +/- 8% vs 32 +/- 13%, P = .003). LA EF after LA catheter ablation was similar among patients with paroxysmal AF and those with chronic AF (21% +/- 8% vs 23 +/- 13%, P = .7). However, LA EF after LA catheter ablation was lower in all patients with AF than in control subjects (21% +/- 10% vs 47% +/- 5%, P < .001).

CONCLUSION

During medium-term follow-up, restoration of sinus rhythm by LACA results in partial return of LA function in patients with chronic AF. However, in patients with paroxysmal AF, LA catheter ablation results in decreased LA function. Whether the impairment in LA function is severe enough to predispose to LA thrombi despite elimination of AF remains to be determined.

A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation

OBJECTIVE

The Cox maze III procedure has excellent long-term efficacy in curing atrial fibrillation. It has not been widely practiced because it is technically challenging and requires prolonged cardiopulmonary bypass. The aim of this study was to examine a simplified Cox maze III procedure that uses bipolar radiofrequency energy as an ablative source.

METHODS

Beginning January 2002, a total of 40 consecutive patients underwent a modified Cox maze III procedure with bipolar radiofrequency energy. Nineteen had a lone maze procedure and 21 had a maze procedure plus a concomitant operation. One month after the operation, the first 8 patients were investigated with high-resolution magnetic resonance imaging. Patients were followed up monthly with clinical examination and electrocardiography.

RESULTS

There was no operative deaths. The crossclamp times were 47 +/- 26 minutes for the modified lone Cox maze III procedure and 92 +/- 37 minutes for the Cox maze III procedure plus concomitant procedures. These were significantly shorter than our previous times for the traditional Cox maze III procedure (93 +/- 34 minutes and 122 +/- 37 minutes, respectively, P <.05). Follow-up magnetic resonance imaging showed no evidence of pulmonary vein stenosis, and atrial contractility was preserved in all patients. There were no late strokes. At 6-month follow-up, 91% of patients (21/23) were in sinus rhythm.

CONCLUSIONS

Bipolar radiofrequency ablation can be used to replace the surgical incisions of the Cox maze procedure. This energy source did not result in pulmonary vein stenosis. The modification of the Cox maze III procedure to use bipolar radiofrequency ablation simplified and shortened this procedure without sacrificing short-term efficacy.

A new device for beating heart bipolar radiofrequency atrial ablation

OBJECTIVE

A technique for mimicking left atrial atriotomies using an ablation device that can be deployed without cardiopulmonary bypass has been developed.

METHODS

In 12 healthy large (35-50 kg) adult pigs, maze-like ablation lesions were directly applied to the left atrial epicardium on the beating heart. The ablation device is irrigated, with a bipolar "hemostat" morphology, utilizing radiofrequency energy. Prior to and after ablation, left atrial electromechanical properties were measured during sinus rhythm in the latest 5 pigs using percutaneous endocardial catheter electromechanical mapping and intracardiac echocardiography. Pathologic analysis was performed acutely.

RESULTS

All ablation lesions demonstrated conduction block along their entire course. Global left atrial conduction time (49.4 +/- 8.8 milliseconds before vs 58.8 +/- 9 milliseconds after) and pattern were not significantly altered. Although a significant amount (17.12% +/- 9%) of myocardium was either ablated or electrically isolated, ablation was not associated with significant alterations in global left atrial mechanics (left atrium ejection fraction 19% before vs 17% after; pulmonary vein peak flow velocity 1.22 m/s before vs 1.38 m/s after; peak mitral inflow velocity 2.34 m/s before vs 2.64 m/s after), mitral valve function, nor left ventricular function. There was no evidence of atrial thrombus formation. Transmurality was achieved in most lesions with no evidence of charring or barotrauma.

CONCLUSIONS

Utilizing this ablation device, atrial lesions similar to the left component of the Maze procedure were deployed with uniform success in a beating heart without cardiopulmonary bypass or atriotomy and without adverse effects on left atrial electromechanics.

Surgical radiofrequency ablation of both atria for atrial fibrillation: results of a multicenter trial

BACKGROUND

The Cox maze procedure has shown to be effective in treating atrial fibrillation. Radiofrequency ablation, with a similar objective, has been used as an adjunct to conventional cardiac surgery for the treatment of atrial fibrillation in more than 20 centers in Australia and New Zealand since March 2000. This is a report of those results.

METHODS

One hundred thirty-two patients in 20 centers underwent radiofrequency ablation as an adjunct to conventional cardiac surgery, with a standardized lesion set created with a flexible, 7-electrode, temperature-controlled probe (Cobra; EPTechnologies, San Jose, Calif). All data were entered into a central registry, with regular follow-up prompted by the registry cocoordinator. Each radiofrequency scar was made with standard parameters requiring 2 minutes of tissue coagulation at 80 degrees C to 85 degrees C. Patients undergoing mitral procedures had radiofrequency ablation performed in the left atrium endocardially. Patients undergoing aortic valve replacement or coronary artery bypass surgery underwent epicardial radiofrequency ablation of the left atrium. Epicardial radiofrequency ablation lesions on the right atrium were common to both groups of patients. Preoperatively, 75% of the patients had chronic atrial fibrillation, 21% had paroxysmal atrial fibrillation, and 4% had flutter. Surgical procedures performed included mitral valve procedure in 60%, coronary artery bypass grafting in 14%, aortic valve replacement in 7%, and coronary artery bypass grafting plus aortic valve replacement in 4%.

RESULTS

There were no major complications related to the use of radiofrequency ablation. There were no soft tissue or cardiac perforations. Ten patients were defibrillated into sinus rhythm within 3 months postoperatively. The freedom from atrial fibrillation was 84% at 3 months, 90% at 6 months, and 100% at 12 months. All patients at 12 and 18 months' follow-up were in sinus rhythm. There were no thromboembolic complications.

CONCLUSIONS

Surgical radiofrequency ablation can be performed safely as an adjunct to conventional cardiac surgery. A standardized lesion set created by using similar temperature settings can be adopted in multiple centers and might be effective in treating atrial fibrillation. Data collection through a central registry has helped in monitoring the effectiveness of this new technique in a scattered population.