Atrial fibrillation surgery – A dedicated approach is the key to success. In-my-opinion

Surgical treatment of atrial fibrillation (AF) began in the late 1980's with the introduction of the Maze procedure by James Cox in St. Louis. Cox and associates started out with WPW-surgery but subsequently turned their attention to AF, performing extensive experimental mapping work both in humans and dogs 1. Their theory was that AF, as interpreted on the ECG, was a result of several electrical macro-reentrant circuits in both atria, creating electrical chaos, and resulting in a fast irregular ventricular rate. Thus, there was a substrate in the atrial myocardium responsible for the maintenance of AF. Cox’ group developed the Maze procedure as a way to break or abolish macro-reentrant circuits anywhere and everywhere in the atria, by surgical incisions and suturing. The pattern of incisions was designed to preclude AF, without interfering with normal AV-conduction, leading to reestablishment of normal sinus rhythm (SR) and atrioventricular synchrony 2. This translated into a major and quite invasive cardiac operation, but the presented results were extraordinary. Cox reported a 98% freedom from AF in 65 patients after two years 3, and subsequent long-term follow-up has been in a similar range 4. The Maze procedure was introduced in Sweden in 1994 and has been performed in over 400 patients in four centers over the years, predominantly as a stand-alone procedure but also in combination with other cardiac operations.

Lately, there has been an increasing interest in this niche of cardiac surgery, and many new, down-sized and less invasive methods have been introduced and evaluated by different surgeons. Surgical incisions have been replaced by intraoperative linear ablation. Surgical ablation by radiofrequency, micro waves, laser, cryo therapy and ultrasound has been reported 5–9, and these new methods have almost exclusively been used in combination with valve or CABG procedures. The rapid development has been eagerly supported by the medical device industry. With these new techniques, success-rates in terms of freedom from AF have been in the 60–80% range. As a result, the role of the classical Maze procedure has diminished. This fact can probably be regarded as a sign of medical progress, but it also brings a problem of consistency and how to interpret what is really the best for a surgical patient with AF. We still don't know what is optimal for the patient in terms of energy source, lesion set and mode of application on the atrial wall; beating-heart epicardially or arrested heart endocardially? The whole field appears quite confusing, partly due to lack of randomized evaluation. Still, AF surgery is now marketed as a new growing frontier for many cardiac surgeons to explore.

However, as more surgeons involve themselves in the mysteries of AF and its surgical treatment, it is very important to take a serious approach to the associated options and problems. In my opinion, this is essential for getting the best possible outcome of AF surgery. First, it is not yet proven that all patients with concomitant AF, scheduled for a CABG or valve procedure, should have an additive arrhythmia procedure with the objective of permanent conversion to SR. Potential benefits for the patient, such as relief of AF symptoms and possible future discontinuation of anticoagulants, must be weighed against the increased risk of a larger operation. For example, pure epicardial ablation procedures may carry an increased risk of thromboembolic complications, and it is vital to rule out left atrial clots by echocardiography preoperatively. The cost of the ablation device also has to be included in the benefit analysis. In summary, these issues should be carefully considered before surgery in each individual patient, in order to keep indications and results scientifically intact.

Secondly, all patients are different, and we should not apply the same surgical therapy in all cases and expect similar results. A history of paroxysmal AF for three months in a CABG patient is most likely not the same as a long-standing permanent AF in a mitral patient with enlarged atria. A paroxysmal short-lasting AF may be consistent with the pulmonary vein trigger theories of Haissaguerre and co-workers 10. However, considering the work of Cox and associates, it seems quite obvious that a permanent AF requires a more extensive lesion set in the atria, at least in the left atrium, to address the substrate of AF. Therefore, the first patient may be helped by pulmonary vein isolation alone, a relatively simple and fast surgical additive procedure, which can be performed by any of the available devices. On the other hand, the second patient most likely requires additional lesions between the pulmonary vein regions on either side, as well as ablation to the mitral annulus and across the coronary sinus 11. These features are all part of the classical “cut-and-sew” Maze procedure, but may pose a challenge for the surgeon using only ablation devices. It is very important for the AF surgeon to form a strategy and a familiarity with this concept, so that a tailored and complete therapy can be applied in each individual patient.

Thirdly, treatment of AF in cardiac surgical patients is really a package of measures, not just the actual ablation itself. Ablate and forget will not lead us to optimal results. Early postoperative AF occurs in >40% of patients undergoing the classical Maze operation 3 and similar figures should be true for ablative procedures. Historically, there has been strong evidence for the process called electrical remodeling in fibrillating atria, i.e. AF begets AF 12. Vice versa, it is likely that SR begets SR in these patients. Therefore, it is important to have an active approach to keeping the surgical AF-patients in SR. They should be carefully monitored in the early postoperative period, with liberal addition of antiarrhythmic medication and/or cardioversion when needed. This may also require a prolonged hospital stay and close in-house collaboration with the cardiologists.

Fourthly, it is vital to know our own local results of AF surgery. In other words, there is no way to know if our AF surgical treatment works unless we have an adequate follow-up of the patients. A well-known and integrated problem in all arrhythmia follow-up is that patients may have asymptomatic recurrences of AF or atrial flutter postoperatively. Therefore, “snap-shot” ECG's may not reflect the true success of the arrhythmia procedure. The simplest way to know more is probably to see these patients at regular intervals postoperatively in the local surgical outpatient clinic, and monitoring can certainly be improved by Holter-ECG's. Arrhythmia results can easily be recorded prospectively in a data base, and this collected information may ease the decision in which patients a postoperative discontinuation of anticoagulants is possible and safe. At this stage, this is a patient group for whom surgeons should involve themselves in a longer perspective. Follow-up of local results is also important for the preoperative discussion with AF patients. They certainly have the right to know the expected risks and outcome of any surgical procedure.

Lastly, the field of surgical AF treatment is moving forward rapidly, and keeping updated is essential for the arrhythmia surgeon. What is true today may not be the method of choice tomorrow. The available evidence seems to point towards more complete ablative lesion-sets, at least in the left atrium, for most cardiac surgical patients with concomitant AF. For patients with lone and medically refractory AF, we know that the classical Maze procedure has a long-lasting success-rate of >90% 13, but many of these patients are now being treated by catheter ablation at an earlier stage. However, as was recently pointed out in an editorial 14, the resources in terms of EP labs and electrophysiologists in Scandinavia may not suffice for the near future, and Maze surgery is still a safe and good alternative for some of these patients. Furthermore, surgeons are now developing thoracoscopic procedures for epicardial ablation without cardiopulmonary bypass 15, and these new methods have already been introduced in Sweden.

In conclusion, as most AF surgery is performed in conjunction with other cardiac operations, it is important for the cardiac surgeon to be dedicated not only to the principal operation, but also to all aspects of the AF procedure. This includes a well-founded preoperative decision, tailoring of the AF procedure, an active postoperative approach to keep the patient in SR, and a close and prolonged follow-up.