Atrial Transport Function Research Articles

Identification of AF Drivers: Toward a Mechanistic Basis of AF Ablation

While the ablation endpoint in patients with paroxysmal atrial fibrillation (AF) has been largely standardized, the optimal approach for patients with persistent AF remains unknown. Among the latter, it is clear that pulmonary vein (PV) isolation alone is insufficient. 1 In an effort to improve outcomes in patients with persistent AF, left atrial (LA) substrate modification has been shown to be effective. 2,3 This may be accomplished by linear ablation and/or ablation of complex, fractionated electrograms (CFAEs). Although CFAEs may be markers of sites that are critical to the fibrillatory process, i.e., drivers, it is also possible that they represent passive phenomena as a result of wave collision, tissue anisotropy, and slow conduction. 4 Even if one uses a relatively stringent definition of a CFAE site, e.g., continuous electrical activity, the likelihood that ablation at such a site will have a favorable impact on the AF cycle length is modest. 5 The fact that such sites may be found away from the PV region in patients with paroxysmal AF also suggests that they may be nonspecific. 6 Also, a randomized study failed to show an incremental benefit of CFAE ablation in patients with persistent AF. 7 Thus, it is possible that CFAE ablation results in more tissue destruction than perhaps necessary to eliminate AF. This has important implications with regards to procedure times, complication rates, and atrial transport function.

A New Vacuum-Assisted Probe for Minimally Invasive Radiofrequency Ablation

The Cobra Adhere XL (Estech, San Ramon, CA) is a multiple-electrode, temperature-controlled, monopolar radiofrequency probe with a vacuum-assisted stabilization system. We evaluated this new technology for epicardial ablation of atrial fibrillation in mitral valve patients through a right mini-thoracotomy. Between June and August 2008, 12 patients underwent minimal invasive surgery for mitral disease and ablation for atrial fibrillation with the Cobra Adhere XL (Estech). Three patients had paroxysmal atrial fibrillation. Off-pump pulmonary vein isolation was performed with an epicardial oval lesion parallel to the mitral plane. In 10 patients, an endocardial lesion to the mitral annulus was added. There were no operative deaths or major postoperative complications. At a mean follow-up of 8.76 +/- 1.0 months, 11 patients (91.67%) were in stable sinus rhythm. Echocardiography underscored a complete recovery of atrial transport function in most of these patients (90.91%). No major cardiac and cerebrovascular events occurred during follow-up. Left-side ablation combined with minimally invasive surgery for mitral disease can be easily, safely, and effectively performed with the Cobra Adhere XL probe.

Recovery of atrial transport function after a maze procedure for atrial fibrillation in conversion of a failing Fontan circulation

Surgical ablation for atrial arrhythmias at conversion of atriopulmonary or ventriculopulmonary Fontan to a total cavopulmonary connection is feasible with recovery of both sinus rhythm and atrial transport function. Recovery of the patient's physical condition may take up to a year. (Neth Heart J 2008;16:170-2.).

Video-Assisted Bilateral Epicardial Pulmonary Vein Isolation for the Treatment of Lone Atrial Fibrillation

This paper aims to evaluate the feasibility and the efficacy of a new off-pump, bilateral thoracoscopic pulmonary vein isolation technique in patients with lone atrial fibrillation. Between April 2004 and February 2006, 26 drug-resistant and symptomatic lone atrial fibrillation patients (18 permanent, 8 paroxysmal) underwent an irrigated radiofrequency ablation procedure using the Cardioblate ablation system (Medtronic, Minnesota). There were 16 men and 10 women with a mean age of 55 +/- 11 years. Mean duration of atrial fibrillation was 34.2 +/- 18.9 months. All patients underwent a bilateral thoracoscopic procedure in which both pulmonary veins were ablated with an atrial cuff using an off-pump epicardial approach. The conduction block was assessed by pacing the pulmonary veins after each ablation. Sixteen patients underwent endoscopic stapling of the left atrial appendage. There were no hospital deaths. All procedures were completed as planned without any conversions to sternotomy. There were no major complications. Follow-up was complete at 6 months, and 80% of the patients were in sinus rhythm (paroxysmal: 100%, permanent: 72%). Of the patients with permanent atrial fibrillation, 85% had regained their atrial transport function. No major thromboembolic event was observed during the follow-up period. The video-assisted bilateral pulmonary vein isolation technique was safe and effective. It was curative for paroxysmal atrial fibrillation patients and effective for permanent atrial fibrillation cases. This technique may find wider application if accumulating data further support these findings.

The Effect of Catheter Ablation for Atrial Fibrillation on Left Atrial Transport Function

The Effect of Catheter Ablation for Atrial Fibrillation on Left Atrial Transport Function

Atrial Pacemaker Complex Preserved Radiofrequency Maze Procedure Reducing the Incidence of Sick Sinus Syndrome in Patients With Atrial Fibrillation

The Cox maze III procedure can effectively restore sinus rhythm in most patients with permanent atrial fibrillation (AF). However, previous studies have shown that the maze procedure results in significant sinus node dysfunction, and, consequently, a considerable number of patients required postoperative pacemaker implantation. This study investigates the hypothesis that the modification of the Cox III maze procedure, to avoid injuring the sinus node and the atrial physiologic pacemaker complex, will reduce the incidence of sick sinus syndrome following surgery. This study investigated 71 patients with permanent AF and mitral valve disease who were undergoing concomitant open-heart surgery. Most atrial incisions in the Cox maze III procedure were replaced with radiofrequency ablation, and the intercaval counterablation was moved posterolaterally to avoid injury to the sinus node and atrial pacemaker complex. At a mean (+/- SD) follow-up time of 46.5 +/- 24 months, 59 patients (83.1%) regained sinus rhythm without receiving antiarrhythmic drug therapy or undergoing electrical cardioversion. The transmitral atrial wave was observed in 44 patients (62%), and the transtricuspid atrial wave was also observed in 53 patients (74.6%). Late sinus node dysfunction developed in only two patients (2.8%), who received permanent pacemaker implantation. This modified radiofrequency maze procedure produces few patients with sick sinus syndrome and effectively restores sinus rhythm and atrial transport function in most patients with permanent AF undergoing concomitant open-heart surgery.

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

The effects of left atrial (LA) circumferential ablation on LA function in patients with atrial fibrillation (AF) have not been well described. The purpose of this study was to determine the effect of LA circumferential ablation on LA function. 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. 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). 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.

Effect of left atrial catheter ablation on left atrial transport function in patients with atrial fibrillation

Effect of left atrial catheter ablation on left atrial transport function in patients with atrial fibrillation

Surgical treatment of atrial fibrillation: a review.

The optimal treatment of atrial fibrillation (AF) depends upon a proper understanding of the electrophysiological basis of its clinical manifestations. Whether AF is continuous (persistent) or intermittent (paroxysmal) depends on variable underlying electrophysiology and determines the choice of interventional treatment. The initiation of intermittent AF requires a "trigger", often, though not always, located near the orifices of pulmonary veins. In contrast, continuous AF does not need a "trigger" to be re-induced repetitively and does not depend on the pulmonary veins or other abnormal automatic foci for its induction or perpetuation. Simple pulmonary vein encircling confines the trigger to the pulmonary veins and, if expertly performed, will cure the majority of patients with intermittent AF. On the other hand, continuous AF requires a Maze procedure or variant thereof to eliminate atrial macro-reentry while allowing sinus rhythm to activate the entire atrial myocardium and preserve atrial transport function. This article reviews the development of the surgical Maze procedure and its implications for the treatment of AF by percutaneous intracardiac or epicardial, minimally invasive techniques. High-intensity focussed ultrasound, a new energy source generating frictional heat, appears promising in the creation of focussed transmural lesions, while preserving the integrity of coronary arterial walls.

Preoperative Atrial Size Predicts the Success of Radiofrequency Maze Procedure for Permanent Atrial Fibrillation in Patients Undergoing Concomitant Valvular Surgery

The radiofrequency (RF) maze procedure can effectively restore sinus rhythm and atrial transport function in the majority of patients with permanent atrial fibrillation (AF) and mitral valve disease. No previous study has described a cutoff value of preoperative atrial size determined by the discriminant analysis in predicting the success of sinus conversion by the RF maze procedure for permanent AF in patients with mitral valve disease. This study included 81 patients with permanent AF and mitral valve disease who underwent the RF maze IV procedure while undergoing concomitant valvular operations. There was one surgical death (1.2%). Another patient died of acute necrotizing pancreatitis 13 months later. Two patients (2.5%) developed sick sinus syndrome and received transvenous permanent pacemaker implantation. In the remaining 77 patients, there were 38 men and 39 women, with a mean (+/- SD) age of 51 +/- 11 years. At a mean follow-up time of 38 months, 65 patients (84.4%) had persistent sinus conversion that had been accomplished by the RF maze procedure (group 1), and 12 patients (15.6%) did not regain sinus rhythm (group 2). We evaluated the preoperative variables between the two groups. Univariate analysis demonstrated that the preoperative left atrial area and the left atrial diameter of group 1 patients were significantly smaller than those of group 2 patients. Group 1 had significantly fewer patients associated with tricuspid valve disease than did group 2. By multiple stepwise logistic regression analysis, only the preoperative left atrial area was an independent determinant of sinus conversion by the RF maze procedure (odds ratio, 0.961; 95% confidence interval, 0.935 to 0.988; p < 0.005). Linear discriminant analysis demonstrated that the sensitivity and specificity of the cutoff value of 56.25 cm(2) of the preoperative left atrial area in predicting the sinus conversion by the RF maze procedure were 50.0% and 86.2%, respectively, and the positive and negative predictive values were 40.0% and 90.3%, respectively. The preoperative left atrial area is an independent determinant of sinus conversion by the RF maze procedure for patients with permanent AF and mitral valve disease.

The standard maze-III procedure

The standard maze-III procedure

Electro cautery maze in chronic atrial fibrillation: An early experinece

The maze procedure is the only surgical treatment that can alleviate the three physiologic sequelae of atrial fibrillation i.e. tachycardia, thromboembolic events and hemodynamic compromise. In the present study, we attempted ablation of atrial fibrillation (AF) using monopolar conventional cautery. is to demonstrate efficacy of electroxcautery maze in chronic AF in patients undergoing mitral valve surgery and long term efficacy of it in maintaining sinus rhythm. In this series 25 patients who underwent electrocautery maze since 2002 were studied, the age ranged from 20–60 years, 60% of patients were females. 20 patients were in NYHA class IV and 5 patients were in class III, who had left atrium (LA) ranging from 5–6.5 cms with LA appendage clot in 8 patients. All patients underwent mitral valve replacement, 3 patients under went tricuspid valve repair and 2 underwent aortic valve replacement as concomitant procedures. The electrocautery maze was done encircling left & right pulmonary veins along with interconnecting portion. Left atrial appendage was ligated only in cases with LA clot. The hospital mortality rate was nil in this group of patients. Freedom from atrial fibrillation or atrial flutter was 92% at 6mths followup. Patients were followed up with regular electrocardiography. Electrocautery maze procedure, an adjunctive procedure is safe, time sparing & effective in eliminating atrial fibrillation & restoring atrial transport function.

Surgical outcome of the maze procedure for atrial fibrillation in mitral valve disease: rheumatic versus degenerative

BackgroundThe results of the maze procedure are known to be less satisfactory in rheumatic mitral disease than in nonrheumatic mitral valve disease. The aim of this study was to determine whether the etiology of mitral valve disease affected surgical outcome. MethodsFrom July 1997 to January 2001, 129 consecutive patients with chronic atrial fibrillation associated with mitral valve disease had mitral valve operations with the maze procedure. The underlying mitral pathology was rheumatic in 86 patients (group R) and degenerative in 43 (group D). Echocardiograms and electrocardiograms were performed immediately and then repeated 3 months and 6 months postoperatively. ResultsThe mean age, duration of atrial fibrillation, and preoperative left atrial size were similar between the groups. There was no operative mortality and no significant difference in cardiopulmonary bypass and aortic cross-clamp times. The sinus conversion rate at 7 days postoperatively was 86% in both groups, and at 6 months it was 95.3% in group R and 97.7% in group D (p > 0.05). The transmitral A wave detection rates in groups R and D at 7 days and 6 months postoperatively were, respectively, 63.1% versus 67.4% and 90.4% versus 91.9% (p > 0.05). The transmitral A wave velocity (cm/second) at the same times (7 days and 6 months postoperatively) was 41.9 ± 41.6 versus 45.5 ± 37.7 and 67.8 ± 38.2 versus 69.8 ± 35.8 in groups R and D, respectively (p > 0.05). ConclusionsThe maze procedure is equally effective in treating chronic atrial fibrillation in patients with either rheumatic or nonrheumatic mitral valve disease in terms of sinus conversion rate and left atrial transport function.

Intraoperative saline-irrigated radiofrequency modified Maze procedure for atrial fibrillation

Background This study was conducted to evaluate the effectiveness of the saline-irrigated radiofrequency modified Maze operation for treatment of chronic atrial fibrillation, and to compare the results of the left and biatrial procedures. Methods During a period of 11 months, 62 patients with chronic atrial fibrillation who were having concomitant cardiac surgery underwent the procedure. The mean age of the patients was 52 ± 14 years. Patients underwent either a biatrial (group A; n = 39) or left atrial (group B; n = 23) procedure. Results Two patients (3.2%) died early in the postoperative period. Three patients (4.8%) required reoperation for bleeding. One patient in group A (1.6%) received a permanent pacemaker. Patients in both groups were free of atrial fibrillation at the end of the procedure (group A: sinus 86.9%, pacemaker 13%; group B: sinus 90.5%, pacemaker 9.5%) ( p > 0.05). At 1-month and longer-term follow-up, sinus rhythm was maintained in 92% and 95% of cases in group A, respectively, whereas this rate was 71% and 81% in group B ( p > 0.05). Holter monitor surveillance revealed a higher rate of atrial fibrillation, atrial arrhythmias, and atrial flutter in group B ( p < 0.05). Transthoracic echocardiography revealed improvement over time in left atrial transport function in both groups ( p < 0.05). Conclusions The saline-irrigated radiofrequency modified Maze procedure was performed safely and efficiently. Both the left and biatrial procedures were successful in terms of restoring sinus rhythm during short-term follow-up. Long-term follow-up with more cases is needed to show the superiority of one method over the other.

Electrical, contractile and structural remodeling during atrial fibrillation.

The natural history of atrial fibrillation (AF) is characterized by a gradual worsening with time. The recent finding that AF itself produces changes in atrial function and structure has provided a possible explanation for the progressive nature of this arrhythmia. Electrical remodeling (shortening of atrial refractoriness) develops within the first days of AF and contributes to an increase in stability of AF. However, 'domestication of AF' must also depend on a 'second factor' since the persistence of AF continues to increase after electrical remodeling has been completed. Atrial contractile remodeling (loss of contractility) leads to a reduced atrial transport function after cardioversion of AF. An important clinical consequence is that during several days after restoration of sinus rhythm, the risk of atrial thrombus formation is still high. In addition, the reduction of atrial contractility during AF may enhance atrial dilatation which may add to the persistence of AF. Tachycardia-induced structural remodeling takes place in a different time domain (weeks to months). Myolysis probably contributes to the loss of atrial contractile force. Although it might explain the loss of efficacy of pharmacological cardioversion and the development of permanent AF, the role of structural remodeling in the progression of AF is still unclear. Atrial structural remodeling also occurs as a result of heart failure and other underlying cardiovascular diseases. The associated atrial fibrosis might explain intra-atrial conduction disturbances and the susceptibility for AF. Thus, both AF itself and the underlying heart disease are responsible for the development of the arrhythmogenic substrate. New strategies for prevention and termination of AF should be build on our knowledge of the mechanisms and time course of AF-induced atrial remodeling.

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

Background. The Maze procedure is a curative surgical therapy for atrial fibrillation, restoring sinus rhythm and improving quality of life. Because the procedure results in tissue scarring, the atrial transport function is most likely affected. Methods. Seventeen patients with paroxysmal atrial fibrillation underwent the Maze III procedure without any concomitant valve operation. Atrial size and transport function were measured before and at 2, 6, and 24 months after operations with two-dimensional echocardiography and pulsed-wave Doppler. Results. Fifteen patients (88%) had signs of left atrial contractions as shown by the presence of a transmitral atrial filling wave on Doppler echocardiography at 6 months follow-up. The transmitral early filling wave and atrial filling wave were measured to calculate the early filling/atrial filling wave ratio, which increased from 1.2 before to 1.9 at 2 months after the Maze procedure (nonsignificant), and further to 2.8 at 24 months ( p = 0.02). A decrease in the right and left atrial size was seen at 2 months after an operation, but no further decrease occurred. Conclusions. In patients with paroxysmal atrial fibrillation, there is a progressive increase in the transmitral early filling/atrial filling wave ratio after the Maze procedure, consistent with a gradual decrease in the left atrial transport function.

Predictors for atrial transport function after mini-maze operation

Background. Restoration of atrial transport function (ATF) is a major goal of the maze procedure. This prospective study was undertaken to evaluate predictors of left atrial transport function in patients undergoing a mini-variant of the maze III procedure 3 and 12 months postoperatively. Methods. Mini-maze operation was performed in 72 patients with a mean age of 64 ± 8.7 years during a 5-year period. Seventy of 72 (97%) had combined procedures. Clinical and electrophysiologic examination was carried out before surgery, and 3 and 12 months postoperatively. Results. Early mortality was 1.4% (1 of 72 patients) and late death occurred in 5.6% (4 of 71 patients). After 3 months, 54 of 68 (80%) patients showed sinus rhythm, and 48 of 60 (80%) after 12 months. ATF was restored in 87% (echocardiography) and 82% (magnetic resonance imaging) after 3 months, and in 86% (echocardiography) and 78% (magnetic resonance imaging) after 12 months. Independent predictors for ATF restoration after 12 months were better preoperative left ventricular function ( p = 0.02), and smaller preoperative left atrial diameter ( p = 0.005). Correlation between echocardiography and magnetic resonance imaging was 80% after 12 months. Conclusions. Restoration of ATF after mini-maze procedure is achieved in over 80%. Independent predictors for ATF restoration are smaller preoperative left atrial diameter and better preoperative left ventricular ejection fraction.

Radiofrequency modified maze in patients with atrial fibrillation undergoing concomitant cardiac surgery

Objective: In the majority of patients with chronic atrial fibrillation the arrhythmia will persist after correction of the underlying structural abnormality. The maze procedure is an effective surgical method to eliminate atrial fibrillation and to restore atrial contractility. Methods: In this study we used radiofrequency energy to create lines of conduction block in both atria during cardiac surgery as a modification of the maze III procedure. One hundred twenty-two patients with atrial fibrillation for at least 1 year and structural heart disease underwent open heart operation and a radiofrequency modified maze procedure. Results: In 108 (89%) of 122 patients mitral valve surgery was performed, and in this group 86 patients (80%) underwent 121 concomitant procedures. Fourteen patients (11%) underwent cardiac surgery not involving the mitral valve. The additional crossclamp time required for the left atrial part of the radiofrequency modified maze procedure was 14 ± 3 minutes. The in-hospital mortality rate was 4.1%. The overall 39-month survival was 90%, and freedom of atrial flutter or atrial fibrillation was 78.5% ± 5.1%. Eighty-nine survivors with sinus, atrial rhythm, or atrioventricular sequential pacemaker had Doppler echocardiography, and right atrial transport function was documented in 83% and left atrial transport function in 77% of patients. Conclusion: We concluded that the radiofrequency modified maze procedure as an adjunctive procedure is safe, time-sparing, and effective in eliminating atrial fibrillation and restoring atrial transport function.J Thorac Cardiovasc Surg 2001;122:249-56

Differential atrial stunning after electrical cardioversion: An echo tissue doppler case study

Left atrial stunning after cardioversion is a well-known phenomenon. It has been associated with higher risk of postcardioversion thromboemboli and increased risk of recurrence of atrial fibrillation. We present a case of differential atrial stunning after electrical cardioversion for atrial fibrillation. Diagnosis was made by pulsed wave Doppler of mitral, tricuspid, and pulmonary vein inflow and mitral and tricuspid annuli. Differential mechanical atrial stunning may be a common phenomenon after cardioversion and may suggest difference in right and left atrial transport function. Its prevalence needs to be determined by a large study. Doppler tissue imaging might be routinely used in patients after cardioversion for atrial fibrillation to detect atrial stunning. (J Am Soc Echocardiogr 2001;14:834-7.)

Serial change in the atrial transport function after the radial incision approach

Background. The left atrial transport function recovers slowly over several months after the maze procedure (Maze), but remains at a low level even during the long-term postoperative period. Because the Maze leaves an insufficient left atrial transport function, patients may still be prone to thromboembolism after the Maze. The radial incision approach (Radial) has been shown to preserve greater atrial transport function than does the Maze in the early postoperative period. Methods. To examine the serial change in the atrial transport function after the Radial, out of 32 patients who underwent the Radial, 15 patients were assessed by transthoracic Doppler echocardiography 1, 3, 6, and 12 months after surgery. The atrial filling fraction and peak A/E velocity ratio were determined from the flow-velocity spectra across the mitral and tricuspid valves. The incidence of thromboembolic events was examined in 21 patients who were followed for more than 3 months after the Radial. The data were compared with data obtained from 13 patients after (41 ± 6 months) the Maze III procedure. Results. The left atrial transport function after the Radial increased within 3 months to a significantly greater level than did that after the Maze in the long-term. The atrial filling fraction was 28.2% ± 7.9% at 3 months after the Radial and 15.1% ± 4.0% at 41 months after the Maze ( p < 0.01). The peak A/E ratio was 0.52 ± 0.18 at 3 months after the Radial and 0.25 ± 0.07 at 41 months after the Maze ( p < 0.01). This increased atrial transport function was maintained for an extended period after the Radial. There were no thromboembolic events in any of the patients after the Radial or Maze, irrespective of postoperative anticoagulant therapy. Conclusions. The Radial approach prevents thromboembolism by restoring sufficient atrial transport function more effectively and faster than does the Maze.