Five-Box Thoracoscopic Maze Outcomes
Earlier Studies
Dr. Sirak has performed over 300 successful totally thoracoscopic maze procedures, beginning in May, 2006. Prior to the advent of the five-box thoracoscopic maze in November, 2008, Dr. Sirak published two previous studies on earlier iterations of the total thoracoscopic maze procedure. The earlier operation did achieve the landmark of the first published series of any minimally invasive anti-AF procedure which included a comprehensive treatment of the left atrium. However, it lacked numerous advancements in technique and instrumentation which were incorporated into the five-box thoracoscopic maze, whose outcomes are discussed below.
In the first of the two previous studies,1 87.5% of a group of patients, nearly all of whom had longstanding persistent atrial fibrillation (no paroxysmal), remained in normal sinus rhythm at 6 months postoperatively without the use of rhythm-control medications. Rhythm surveillance consisted of a week of continuous self-actuated event monitoring at 3, 6, and 13 months postoperatively. The notable result of this study is that the high success rate in this most difficult group of patients was achieved prior to the availability of a linear ablation device designed for the extended lesions on the left atrium. Moreover, the verification technique employed in this study, electrogram attenuation, has been discarded in favor of the more rigorous standard of bidirectional block. In the second study,2 91% of a similar group consisting almost entirely of people with longstanding persistent atrial fibrillation remained in normal sinus rhythm at 6 months without the use of rhythm-control medicines and with the same surveillance protocol.
Five-Box Thoracoscopic Maze Results
In a paper published in the September, 2010 issue of the Annals of Thoracic Surgery, 48 patients with longstanding persistent AF (duration 1-20 years, mean 4.3 years) underwent the five-box thoracoscopic maze. 13 patients had previously undergone one or more percutaneous ablation procedures. The mean left atrial diameter was 4.5 cm (range 3.4-6.3 cm). Rhythm surveillance for all patients consisted of one week of continuous self-actuated event monitoring at 3, 6, 13, and 24 months postoperatively.
All anti-arrhythmia medications are discontinued by the end of the second postoperative month. At the three-month interval, 34 of 36 (94%) patients were free of atrial fibrillation. Interestingly, one of the failed patients experienced a single symptomatic 10-minute episode of atrial fibrillation which self-terminated; the patient remained in sinus rhythm through the six-month monitoring. The other patient was mapped and treated percutaneously for cavotricuspid flutter—an endocardial lesion which, strictly speaking, is not part of any epicardial ablation procedure. At the six-month interval, 19 of 19 patients were free of atrial fibrillation. At the 13-month interval, four of four patients were free of atrial fibrillation.
Dr. Sirak has submitted updated five-box thoracoscopic maze data in an abstract for oral presentation at the Society of Thoracic Surgeons meeting in January 2011. In 70 patients, freedom from atrial fibrillation was observed in 44 of 46 patients at 3 months, 25 of 26 patients at 6 months, and 7 of 7 patients at 13 months; only 1 patient remained on low-dose anti-arrhythmia (sotalol) therapy.
Comparison with Percutaneous (Catheter) Ablation
Percutaneous ablation, also known as catheter ablation describes a procedure in which long catheters are inserted into the femoral vein and advanced into the heart. Indirect imaging, such as echocardiography and x-ray fluoroscopy, and electrical sensing are used to position the ablation catheter. Current techniques direct ablations to the inside surfaces of the heart to target specific anatomic structures, such as the pulmonary veins, and areas of electrical instability as detected by a sensing catheter.
However, extended lines to isolate arrhythmogenic areas of the heart are created not as true continuous lesions, as in the five-box thoracoscopic maze surgery, but as a series of spot ablations directed by necessarily imprecise imaging modalities. Without direct visualization of the ablation, and without a true linear ablation probe, the extended lesions performed with a catheter do not block errant electrical signals with the same reliability as those used in the five-box thoracoscopic maze.
In fact, in all patients referred The Ohio State University after failed catheter ablation, intraoperative testing of the pulmonary vein isolation from their previous catheter ablation has consistently demonstrated failure of isolation. The inability of catheter ablation to achieve this most basic goal of any anti-arrhythmia procedure illustrates the significant limitations of the technique.
These limitations emerge particularly in outcomes in patients with persistent, or non-self-terminating, atrial fibrillation. As reported recently in the journal Circulation: Arrhythmia and Electrophysiology, only 40% of this group of patients was successfully treated with a single catheter ablation. The reason for the substantial difference in outcomes between the five-box thoracoscopic maze and catheter ablation is clear. In comparison to the linear ablation technology of the five-box thoracoscopic maze, the spot ablation techniques of catheter ablation are inefficient and unreliable for isolating arrhythmia-generating regions of the heart.
More Information
For more details about atrial fibrillation treatments, including the five-box thoracoscopic maze procedure, request a phone consultation with Dr. John Sirak or call his appointment phone at (614) 366-7414.
1. Sirak et al., Toward a Definitive, Totally Thoracoscopic Procedure for Atrial Fibrillation. Annals of Thoracic Surgery 2008; 86, 1960-64.
2. Sirak et al., Toward a Definitive, Totally Thoracoscopic Procedure for Atrial Fibrillation. American Heart Association Scientific Sessions 2008, Poster Presentation.