Concomitant Cox maze IV procedures are ablations performed during other heart surgeries. While they generally have high success rates of over 70%, reported success rates can vary for several reasons, including those below. Many of these same variables apply to standalone Cox maze IV procedures for afib only.
Severity of afib. Most data on surgical ablation comes from observational (informal) studies at single hospitals, not formal clinical trials. These centers typically aggregate the data for all surgical ablation procedures, meaning the overall effectiveness rate includes paroxysmal, persistent, and even longstanding persistent afib. More severe forms of atrial fibrillation are more difficult to cure because of atrial remodeling. A center’s overall effectiveness rate depends, in part, on the primary afib type treated at the center.
Other heart conditions. The effectiveness rate of afib ablation can vary based on the other heart condition(s) being treated. For instance, 92% of patients who had a valve procedure in the ABLATE (AtriCure Bipolar Radiofrequency Ablation of Permanent Atrial Fibrillation) trial were free from afib and off antiarrhythmic medication at six months. Comparatively, 78% of patients who underwent coronary artery bypass grafting met this study endpoint.
Techniques. “Maze” has become a catch-all term to describe any surgical ablation procedure. However, some surgeons only apply ablation lines in the left side of the heart. In contrast, a true maze procedure involves the ablation of tissue in both the left and right atria. The HRS Consensus Statement update in 2012 stated that the term “maze” should only refer to bi-atrial ablations.1 The varying techniques used can affect outcomes, which is another reason it’s difficult to pinpoint an overall effectiveness rate for concomitant procedures.
Energy sources. Surgical ablation can be performed with various energy sources. These can include bipolar radiofrequency, unipolar radiofrequency, and cryothermy. Research has shown these energy sources have varying abilities to create transmural lesions. Transmurality is critical to a procedure’s ability to stop atrial fibrillation.2 The HRS Consensus Statement suggests that bipolar radiofrequency clamps are better at creating transmural lesions than unipolar radiofrequency devices or other energy sources.1
Differing study protocols. Many studies on concomitant ablation were published before the release of the first HRS Consensus Statement (2007).3 These studies, and some published after 2007, use follow-up periods and monitoring techniques that make it difficult to ascertain the effectiveness rate. For instance, many studies used a follow-up period of “last patient visit” rather than freedom from atrial fibrillation at one year. Similarly, some studies did not use 24- or 48-hour Holter monitors to assess whether the patient was free from afib. In the future, surgical ablation results will likely use the same follow-up periods and monitoring as those for catheter ablation based on efforts by leading afib surgeons to standardize the reporting methods.
The ABLATE clinical trial evaluated the effectiveness and safety of treating persistent and longstanding persistent afib during open-heart surgery for coronary artery bypass grafting or valve replacement or repair. Surgeons used the bipolar radiofrequency clamp to scar tissue in the Cox maze IV lesion pattern. ABLATE’s effectiveness endpoint was freedom from afib and antiarrhythmic medication at six months. Of the 55 patients enrolled in the study, 74% met the study endpoint.
The CURE-AF (Concomitant Utilization of Radio Frequency Energy for Atrial Fibrillation) study also evaluated patients with persistent and longstanding afib. CURE-AF enrolled 150 patients who were treated with the irrigated radiofrequency clamp. The CURE-AF study instructed surgeons to scar tissue in the Cox maze IV lesion pattern. At six to nine months, 66% of patients were free from atrial fibrillation, and 53% were free from afib and antiarrhythmic medication. However, there was a wide variance between centers’ success rates. Some had low freedom from afib rates of only 33%, whereas others achieved 100% success. The principal investigators for the study concluded that higher success was achieved at centers that performed the full Maze IV lesion pattern. The safety event rate was 6.6% at 30 days.
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If you’re considering a Cox maze IV surgical ablation procedure for your afib, with or without other heart issues, see Maze Procedure Risks and Are You a Candidate for a Maze Procedure.
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