The surgical treatment of atrial fibrillation with microwave ablation: preliminary experience and results

Microwave Ablation in Mitral Valve Surgery for Atrial Fibrillation (MAMA)

Objective: Microwave ablation in conjunction with open heart surgery is effective in restoring sinus rhythm (SR) in patients with atrial fibrillation (AF). In patients assigned for isolated mitral valve surgery no prospective randomized trial has reported its efficacy. Methods: 70 patients with longlasting AF where included from 5 different centres. They were randomly assigned to mitral valve surgery and atrial microwave ablation or mitral valve surgery alone. Results: Out of 70 randomized, 66 and 64 patients were available for evaluation at 6 and 12 months. At 12 months SR was restored and preserved in 71.0 % in the ablation group vs 36.4 % in the control group (P=0.006), corresponding figures at 6 months was 62.5 % vs 26.5 % (P=0.003). The 30-day mortality rate was 1.4 %, with one death in the ablation group vs zero deaths in the control group. At 12 months the mortality rate was 7,1 % (Ablation n=3 vs Control n=2). No significant differences existed between the groups with regard to the overall rate of serious adverse events (SAE) during the perioperative period or at the end of the study. 16 % of patients randomized to ablation were on antiarrhytmic drugs compared to 6 % in the control group after 1 year (p=0.22). Conclusion: Microwave ablation of left and right atrium in conjunction with mitral valve surgery is safe and effectively restores sinus rhythm in patients with longlasting AF as compared to mitral valve surgery alone.

Alternative energy sources for surgical treatment of atrial fibrillation in patients undergoing mitral valve surgery: microwave ablation vs cryoablation

The study aim was to compare maze outcomes using microwave ablation or cryoablation in patients with mitral disease and atrial fibrillation (AF). Between 1999 and 2005, 340 patients underwent mitral valve surgery and concomitant maze procedure involving either microwave ablation (n=96, MW group) or cryoablation (n=244, Cryo group). Mean age at operation was 50.0±12.5 yr. Follow-up period was 46.1±28.2 months. The Cryo group showed a longer aortic clamping time than the MW group (P=0.005). There were no differences in operative mortality and morbidity rates. The unadjusted 5-yr AF free rate was 61.3±1.2% in the MW group and 79.9±3.2% in the Cryo group (P=0.089). After adjustment, the MW group only showed a tendency toward more frequent AF recurrence than the Cryo group (Hazard ration 1.66, 95% confidence interval 0.89 to 3.07). Multivariate analysis revealed that older patient age (P<0.001) and greater left atrial size (P<0.001) were independent risk factors for AF recurrence. Although the use of microwave ablation results in shorter aortic clamping time, it has a tendency toward more frequent late AF recurrence than with cryoablation.

Permanent Chronic Atrial Fibrillation: Is Pulmonary Vein Isolation Alone Enough?

BACKGROUND

The efficacy of mere pulmonary vein isolation epicardially for the treatment of permanent chronic atrial fibrillation, in comparison with the left atrial endocardial maze procedure was evaluated.

METHODS

Retrospective data collection and analysis toward the outcome of 72 consecutive patients who underwent left atrial maze procedures between January 2003 and December 2005 was performed. Surgical ablation was performed concomitantly with valve and (or) coronary procedures. Group I (n = 29) received an endocardial left atrial ablation using unipolar saline irrigated radiofrequency (Medtronic Cardioblate surgical ablation pen; Medtronic Inc, Minneapolis, MN). Group II (n = 43) received epicardial isolation of the pulmonary veins using bipolar saline irrigated radiofrequency (Medtronic Cardioblate). Follow-up included 24h electrocardiogram and echocardiography 6 and 12 months postoperatively.

RESULTS

Mean follow-up was 19.5 +/- 1.0 months (17.7 +/- 19.5 months group I vs 20.6 +/- 1.1 months group II). Both groups were comparable with regard to duration of preoperative atrial fibrillation, European system for cardiac operative risk evaluation, left ventricular ejection fraction, aortic cross-clamp time, bypass time, intensive care unit and hospital stay (p > 0.05). No maze procedure-related mortality was observed. In group I, three patients required postoperative pacemaker implantation due to atrioventricular (AV) bloc, bradycardia, and sick sinus syndrome, respectively. In group II, five patients required postoperative pacemaker implantation (three AV bloc and two bradycardia). Freedom from atrial fibrillation at last follow-up was 85.7% and 58.5% in groups I and II, respectively (p = 0.016).

CONCLUSIONS

Pulmonary vein isolation alone seems to be insufficient in treating permanent chronic atrial fibrillation. In case of chronic permanent atrial fibrillation, left atrial endocardial maze, providing the connection lines to the mitral annulus and (or) between the pulmonary veins, seems to be mandatory.

Surgical treatment of atrial fibrillation : a systematic review

BACKGROUND

The recently published overwhelming number of publications on the surgical treatment of AF, using a wide variety of techniques, blurred any precise appreciation of the nowadays surgical treatment of AF. As a consequence, the "state of the art" of the surgical technique of AF is ill-defined.

OBJECTIVES

In this review the efficacy of the alternative sources of energy (radiofrequency-microwave and cryoablation; (group I) and the classical "cut and sew" Cox-Maze III (group II), which claims a 97-99% sinus rhythm (SR) success rate, were evaluated in the surgical treatment of atrial fibrillation (AF).

METHODS

A computerized search in the PubMed and Medline database was conducted. Only original, English written, clinical manuscripts on the surgical treatment of atrial fibrillation citing the clinical outcome, including the postoperative sinus rhythm, were included. The following data were registered: the absolute numbers and percentages of treated patients, gender (male versus female) distribution, the type of arrhythmia (permanent or paroxysmal AF), type of surgery (mitral or non-mitral valve or a lone AF surgical procedure), postoperative morbidity (bleeding, the use of an intra-aortic balloon pump, cerebral vascular accident), postoperative pacemaker implantations, 30-day mortality, survival and sinus rhythm conversion. The mean values for age (years), left atrial diameter (mm), preoperative duration of AF (years) and left ventricular ejection fraction (%) were also recorded.

RESULTS

Forty-eight studies were included comprising 3832 patients: 2279 in group I and 1553 in group II. The mean duration of AF, left atrial diameter and LVEF were 5.4 versus 5.5 years (p=0.90), 55.5 versus 57.8 mm (p=0.23) and 57 versus 58% (p=0.63). The postoperative SR rates for group I and II were 78.3 versus 84.9% (p=0.03). However, the "cut and sew" Cox-Maze III was conducted in younger patients (55.0 versus 61.2 years; p=0.005), more often to treat paroxysmal (22.9 versus 8.0%) and lone AF (19.3 versus 1.6%). Alternative sources of energy were predominantly used to treat permanent AF (92.0%), almost always as a concomitant surgical procedure (98.4%) and increasingly in combination with non-mitral valve surgery (18.5%). After correction for these variations, the postoperative SR conversion rates for group I and II did not differ significantly anymore.

CONCLUSIONS

We could not identify any significant difference in the postoperative SR conversion rates between the classical 'cut and sew' and the alternative sources of energy, which were used to treat atrial fibrillation.