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

Q: What is the clinical evidence from this study?

Study design: RCT. Population: Longlasting atrial fibrillation in patients scheduled for mitral valve surgery (n=70). Intervention: Concomitant biatrial endocardial microwave ablation plus mitral valve surgery vs. Mitral valve surgery alone. Primary outcome: Preserved sinus rhythm at 12 months follow-up determined by 12-lead ECG (without documented episodes or cardioversion of AF, AFL, or AT since previous follow-up) (p=0.006).

Anders Jönsson; Mika Lehto; Henrik Ahn; Ulf Hermansson; Peter G. Linde; Anders Ahlsson; Juhani Koı̈stinen; Jukka Savola; Pekka Raatikainen; Martti Lepojärvi; Antero Sahlman; Kalervo Werkkala; Lauri Toivonen; Håkan Walfridsson

doi:10.4022/jafib.432

August 20, 2012

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

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Key result

Biatrial microwave ablation nearly doubles 1-year sinus rhythm maintenance after mitral valve surgery to ~71%.

P=0.006
n=70

Why the study?

Microwave ablation during open heart surgery restores sinus rhythm in patients with AF, but no prospective randomized trial had reported its efficacy in patients undergoing isolated mitral valve surgery.

Does concomitant biatrial microwave ablation improve sinus rhythm restoration and preservation at 12 months compared to mitral valve surgery alone in patients with longlasting atrial fibrillation undergoing mitral valve surgery?

Key Points

To assess the efficacy and safety of adding microwave ablation to mitral valve surgery for restoring sinus rhythm in patients with longlasting atrial fibrillation.
Multicenter randomized trial of 70 patients with longlasting atrial fibrillation across 5 centers assigned to mitral valve surgery plus microwave ablation (n=35) or mitral valve surgery alone (n=35).
Microwave ablation of the left and right atrium added an operative time of 17.5 ± 5.1 minutes.
Outcomes were evaluated with 12-lead and 24-hour Holter electrocardiography at 6 and 12 months postoperatively.
At 12 months, sinus rhythm was restored and preserved in 71.0% (22/31) of the ablation group versus 36.4% (12/33) of controls (P=0.006); at 6 months, rates were 62.5% (20/32) versus 26.5% (9/34) (P=0.003).
Holter monitoring at 12 months revealed freedom from atrial arrhythmias in 70.0% (21/30) of ablation patients versus 33.3% (9/27) of controls (P=0.012).

Study Design

Type

RCT (n=70)

Blinding

Single-blind (patients and all follow-up personnel were blinded; surgical team was unblinded)

Randomization

Computer-based randomization performed by an external resource and stratified by hospital using sealed envelopes

Multicenter

Yes

Structured PICO

Does concomitant biatrial microwave ablation improve sinus rhythm restoration and preservation at 12 months compared to mitral valve surgery alone in patients with longlasting atrial fibrillation undergoing mitral valve surgery?

P

Population

70 adults with longlasting continuous atrial fibrillation undergoing mitral valve surgery at 5 centers in Sweden and Finland, followed for 12 months.

I

Intervention

Mitral valve surgery plus concomitant biatrial endocardial microwave ablation (2.45 GHz microwave generator with FLEX 2 probe at 40 W for 25 seconds or FLEX 4 probe at 65 W for 60 seconds; mean ablation time 17.5 ± 5.1 min) and left atrial appendage excision or exclusion.

C

Comparator

Mitral valve surgery alone (both groups received preoperative and postoperative bisoprolol, postoperative atrial overdrive pacing for 5 days if in sinus rhythm, warfarin for at least 3 months, and sotalol or amiodarone for early recurrent paroxysmal AF).

O

Outcome

Preserved sinus rhythm at 12 months follow-up determined by 12-lead ECG (defined as sinus rhythm on 12-lead ECG without any documented episodes or cardioversion of atrial fibrillation, atrial flutter, or atrial tachycardia since previous follow-up).surrogate

Main Result

Absolute Event Rate: 71% vs 36.4%

p-value: p=0.006

Concomitant biatrial microwave ablation during mitral valve surgery safely and significantly doubles the rate of sinus rhythm restoration at 1 year compared to mitral valve surgery alone in patients with longstanding persistent atrial fibrillation.

Limitations

Rhythm outcome was determined only by 12-lead ECG and 24-hour Holter ECG, which may underestimate the true burden of asymptomatic paroxysmal AF, AT, and AFL.
Not all patients were off antiarrhythmic drugs (sotalol) when analyzing the primary endpoint at 12 months, which could act as a confounding factor.
Formation of transmural lesions was not confirmed at surgery by electrophysiological mapping.
Only 12-lead ECG and 24-hour Holter ECG were used to determine rhythm outcome, potentially underestimating asymptomatic paroxysmal AF, AT, and AFL
Some patients remained on antiarrhythmic drugs (sotalol) at the 12-month primary endpoint analysis, acting as a potential confounding factor
Transmurality of ablation lesions was not confirmed intraoperatively by electrophysiological mapping

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Implication

Supports concomitant biatrial microwave ablation during mitral valve surgery for longlasting AF; confirms efficacy in an RCT.

Abstract

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.

Discussion

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Cite This Study

Jönsson et al. (2012) conducted an RCT in Longlasting atrial fibrillation in patients scheduled for mitral valve surgery (n=70). Concomitant biatrial endocardial microwave ablation plus mitral valve surgery vs. Mitral valve surgery alone was evaluated on Preserved sinus rhythm at 12 months follow-up determined by 12-lead ECG (without documented episodes or cardioversion of AF, AFL, or AT since previous follow-up) (p=0.006). Concomitant biatrial microwave ablation during mitral valve surgery restored and preserved sinus rhythm at 12 months in 71.0% of patients compared to 36.4% with mitral valve surgery alone (P=0.006).

synapsesocial.com/papers/6a74bda199129e9915f55119 https://doi.org/10.4022/jafib.432

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

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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