Surgical Ablation of Atrial Fibrillation

Comparison of the outcomes of monopolar and bipolar radiofrequency ablation in surgical treatment of atrial fibrillation

OBJECTIVE

To compare the therapeutic effects and safety of monopolar and bipolar radiofrequency (RF) ablation used during cardiac surgery to treat atrial fibrillation.

METHODS

We retrospectively studied a total of 81 patients with chronic atrial fibrillation who underwent open cardiac surgery with concomitant RF ablation between January 2007 and March 2011. Fifty-eight patients received bipolar RF ablation and 23 received monopolar RF ablation, respectively. The sinus rhythm restoration rate, the procedural duration, the frequency of severe perioperative complications, and mortality were compared between the two groups.

RESULTS

The sinus rhythm restoration rate did not differ significantly between the two groups after follow-up of 15.1 ± 12.6 months (P=0.199). The frequencies of severe perioperative complications and mortality were also similar in the two groups. The total procedural time using bipolar RF ablation was significantly shorter than that using monopolar ablation (19.7 ± 4.6 minutes vs. 28.1 ± 8.5 minutes, P< 0.001).

CONCLUSIONS

Both monopolar and bipolar RF ablation are safe and effective in treating chronic atrial fibrillation patients during open cardiac surgery, but bipolar RF ablation is more convenient in practice.

Surgical treatment of lone atrial fibrillation by mid-sternotomy Maze procedure under standard cardiopulmonary bypass

The aim of article is to give a brief description to the surgical strategies for patients with lone atrial fibrillation without associated cardiac operations, and present the possible indications of on-pump Maze procedures through a mid-sternotomy approach.

Minimally invasive surgical release of entrapped mapping catheter in the mitral valve

Two cases of catheter entrapment in the mitral valve, which is a rare complication of pulmonary vein isolation, were successfully treated via robot-assisted minimally invasive surgery.

Pilot study of transesophageal endoscopic epicardial coagulation by submucosal endoscopy with the mucosal flap safety valve technique (with videos)

BACKGROUND

We previously demonstrated that the thoracic cavity could be safely accessed by submucosal endoscopy with the mucosal flap safety valve (SEMF) technique.

OBJECTIVES

To evaluate the technical feasibility of transesophageal access to the heart and epicardial ablation.

DESIGN

One-week survival study with 5 porcine models.

SETTINGS

Animal laboratory with general anesthesia.

INTERVENTIONS

High-pressure carbon dioxide injection and balloon dissection created a large submucosal working space for insertion of a cap-fitted endoscope. A myotomy was performed inside the submucosal space. The thoracic cavity was endoscopically accessed through the myotomy site. A pericardial window was created with a needle-knife. A spot coagulation of the epicardium was performed with a heat probe and a hook-knife. The myotomy site was sealed with the overlying mucosal flap, and the mucosal entry site was closed with clips.

MAIN OUTCOME MEASUREMENTS

An endoscopy and a necropsy were performed to study the esophagus, mediastinum, pericardial space, and cautery locations on the epicardium one week after the procedure.

RESULTS

Epicardial coagulation was successfully performed within 30 minutes in 4 of the 5 pigs. Follow-up endoscopy demonstrated completely sealed myotomy sites by the overlying mucosal flap. There was no gross contamination or signs of contamination in the thoracic cavity. The pericardial space was normal in appearance. The epicardial coagulation sites were healing, without exudative ulceration.

CONCLUSIONS

The SEMF technique allowed endoscopic access to the upper mediastinum, the pericardium, and the epicardium via the esophagus, along with a minimal intervention on the epicardium.

Atrial function after ablation procedure in patients with chronic atrial fibrillation using steady-state free precession magnetic resonance imaging

BACKGROUND

Surgical ablation procedures are an established surgical procedure for restoration of sinus rhythm and reestablishment of atrial function in patients with chronic atrial fibrillation. The purpose of this study was to evaluate the feasibility and reproducibility of steady-state free precession magnetic resonance imaging (SSFP MRI) for examination of atrial dimensions and function after ablation procedures.

METHODS

Nineteen patients (mean age, 63.1 +/- 11.7 years) being at least six months after surgical ablation procedure, with stable sinus rhythm, were selected for the study. They underwent cardiac MRI. End-diastolic and end-systolic volumes were measured using Simpson's rule. The presence of visual contraction was visually assessed.

RESULTS

In MRI evaluation mean end-diastolic volume of the right atrium and left atrium after an ablation procedure was 127 +/- 45 mL and 163 +/- 50 mL, respectively. Mean stroke volume was 23 +/- 15 mL and 26 +/- 12 mL for the right and left atrium. Mean ejection fraction of the right atrium was 0.19 +/- 0.14 and 0.17 +/- 0.1 for the left atrium. An atrial kick of both atria was observed in 8 of 19 (47%) patients. An atrial kick of only the right atrium was observed in an additional 13 of 19 (68%) patients.

CONCLUSIONS

The anticipated events after a surgical ablation procedure are the restoration of atrial contractility and the associated atrial kick, thereby enhancing cardiac output and decreasing the risk of thromboembolism. Evaluation of atrial function after an ablation procedure using SSFP MRI is feasible and allows a standardized documentation of postoperative atrial function, thus allowing evaluation of the surgical outcome in a reproducible way. Echocardiographic evaluation seems to underestimate the transport function of the atrium.

Surgical approaches for atrial fibrillation

The Cox Maze procedure, a cardiac intervention that was developed by James Cox, MD, was first performed in 1988 to surgically cure atrial fibrillation. Over the years, changes in techniques of the classic maze were made, culminating in the Cox Maze III procedure, the Gold Standard. Modifications in the original procedure included simplifying the procedure to a minimally invasive approach. As a result of some of these modifications, the initial maze-like series of surgical atrial incisions has been reduced with the use of alternate energy sources that create hyperthermic lesion lines of conduction block that isolate and interrupt the abnormal impulses. The minimize, a minimally invasive thorascopic approach, can be performed off pump, thus avoiding a median sternotomy and cardiopulmonary bypass and cardioplegic arrest intraoperatively and ensuring a shorter, less painful recovery.

An experimental sheep model used to develop an ablation procedure for chronic atrial fibrillation

BACKGROUND

Atrial fibrillation is the most common form of serious arrhythmia in humans. The therapeutic options offered are medical, surgical, and interventional. The surgical approach is justified in cases of atrial fibrillation already subjected to cardiac surgery for an associated organic heart disease such as a valvular or ischemic disease. A minimally invasive surgical approach is needed to extend the possibility of surgical treatment to patients with lone atrial fibrillation and those who cannot be treated by interventional procedures. This study aimed to use sheep as an experimental model in developing a minimally invasive surgical procedure for chronic atrial fibrillation therapy in humans.

METHODS

The investigation was conducted with 20 animals using a video-assisted thoracoscopic approach, in which a flexible microwave energy ablating probe was positioned on the epicardial surface encircling the pulmonary veins.

RESULTS

In 10 of the 20 animals, it was possible to encircle the pulmonary veins using the thoracoscopic approach in less than 3 h without major complications.

CONCLUSION

The epicardial ablation procedure using the thoracoscopic approach is feasible, safe, and reproducible.

Analysis of the left atrial appendage by magnetic resonance angiography in patients with atrial fibrillation

BACKGROUND

Recent interest has focused on the left atrial appendage (LAA) in the setting of atrial fibrillation as a potential source of thromboembolism and stroke, which may be amenable to permanent occlusion by a variety of investigational catheter-delivered devices. Precise anatomic characterization of the LAA is necessary to determine the suitability of a patient for device placement and for device selection and sizing.

OBJECTIVES

The purpose of this study was to perform detailed three-dimensional characterization of LAA size and geometry by magnetic resonance angiography.

METHODS

Fifty patients with chronic atrial fibrillation undergoing cardiac magnetic resonance angiography in preparation for catheter ablation of atrial fibrillation were analyzed for LAA volume, neck size, depth, and overall geometry.

RESULTS

The average LAA volume was 17.3 +/- 6.7 mL, with a depth of 26.6 +/- 4.9 mm and a "neck" diameter of 20.0 +/- 5.3 mm x 14.1 +/- 4.7 mm. The average number of LAA lobes was 1.4 +/- 0.7 (range 1-4). Substantial interpatient variability was present in the relative dimensions and morphology of the LAA. There was a significant correlation between left atrial size and LAA neck dimensions.

CONCLUSION

There is significant heterogeneity in LAA size and dimensions among patients with atrial fibrillation. Device occlusion of the LAA may require devices that are available in multiple sizes/shapes or that can adapt to this heterogeneity.

Multislice Computed Tomography Accurately Quantifies Left Atrial Size and Function After the MAZE Procedure

Background— Although the MAZE procedure allows for the recovery of sinus rhythm and left atrial (LA) mechanical function in the great majority of patients with chronic atrial fibrillation (AF), the effects of MAZE on the precise LA geometry and wall motion remain to be elucidated. We hypothesized that LA size and mechanical function in patients with chronic AF and mitral valvular disease are well restored after MAZE.

Methods and Results— We studied 14 patients (MAZE group: mean±SD age, 63.9±8.6 years; 8 men and 6 women) who underwent MAZE for chronic AF and mitral valve surgery and 10 patients with sinus rhythm (coronary artery bypass graft [CABG] group: age, 70.0±7.9 years; 5 men and 5 women) who underwent CABG at Takeda Hospital between February 2002 and September 2005. MAZE was conducted by the endocardial application of radiofrequency ablation with a temperature-controlled multipolar radiofrequency catheter. LA volume and booster function were quantitatively evaluated by multislice computed tomography at 17.9±10.0 months (MAZE group) and 15.3±13.6 months (CABG group) postoperatively. All patients with MAZE were free of AF and other atrial arrhythmias during the follow-up period. In the CABG group, LA maximal and minimal volumes and ejection fraction were 109±12 mL, 82±11 mL, and 26±10%, respectively. In the MAZE group, LA maximal volume was 139±17 mL ( P =0.187 versus CABG), and LA minimal volume was 121±16 mL ( P =0.082 versus CABG), with an ejection fraction of 15±7% ( P =0.004 versus CABG). In both groups, all parts of the LA wall contracted toward the geometric center of the LA. The extent of wall motion was significantly worse in the MAZE group compared with the CABG group. In both groups, LA booster function was inversely correlated with LA maximal volume.

Conclusions— MAZE with radiofrequency ablation is safe and effective for the restoration of sinus rhythm in patients with chronic AF and mitral valve disease. However, chronic AF associated with mitral valve disease deteriorates LA mechanical function diffusely throughout the LA wall. Further studies with the use of multislice computed tomography are needed to sequentially evaluate LA function after MAZE in patients with and without mitral valve surgery.

Is Helicobacter pylori a cause of atrial fibrillation?

Inflammation has been implicated in the pathogenesis of cardiovascular diseases. C-reactive protein, a sensitive marker of systemic inflammation, has recently been reported to be significantly higher in patients with atrial fibrillation (AF) compared with a control group with no history of atrial arrhythmia. Elevated C-reactive protein levels in patients with AF reflects an underlying inflammatory process. Histological anomalies in the atria of patients with AF have also been observed. These anomalies may have an inflammatory basis, although it is not known if any structural changes within the atria are a cause or a consequence of the arrhythmia. Ongoing chronic infection(s) has been suggested as a possible cause of the inflammatory process demonstrated in patients with AF. Helicobacter pylori, a Gram-negative bacterium more commonly known for infecting the gastric mucosa and causing peptic ulcers, is a noncardiac factor that has been controversially reported to be associated with cardiovascular diseases. This article gives a brief overview of AF and specifically explores the recent evidence that suggests that Helicobacter pylori infection causes AF.