Role of catheter and surgical ablation in congenital heart disease

The role of surgery and radiofrequency current ablation for the treatment of tachycardias in patients with congenital heart disease The use of radiofrequency current application as a treatment strategy has stimulated a revolution in our understanding of tachycardia mechanisms. The extension of its use to patients with congenital heart defects and tachyarrhythmias has opened the door to new treatments with known success rates and known risks for mortality and morbidity. Antiarrhythmic surgery aims to dissect or excavate a responsible substrate and is especially worth considering if cardiac surgery is being undertaken for other reasons. With suitable surgical skill and interest, and with strong electrophysiologic support, high success rates have been documented. Antiarrhythmic surgical incisions have the advantage of being visually controllable regarding the extent and location of damage to myocardial tissue. In other situations, radiofrequency current ablation is preferred because of its less-invasive character, its use of local anesthesia, and the avoidance of surgical trauma. Both surgery and catheter ablation require precise clarification of the tachycardia mechanism and precise localization of the underlying substrate. The importation of such techniques into the realm of open chest surgery would be difficult in light of the need for multiple intracardiac catheters and repeated fluoroscopically guided catheter positioning. Electrophysiologic studies performed during the antiarrhythmic surgical procedure cannot provide complete information, and their use is thus restricted to the arrhythmogenic myocardial target only [32,45]. In contrast, catheter-mediated electrophysiologic studies offer the option of exact diagnosis, precise substrate localization, and interventional treatment in a single session. Moreover, validation of the linear lesion's completeness has become a reliable predictor for mid- and long-term success in avoiding recurrences. As a result, the application of catheter-mediated ablation has exploded within the past 15 years. Antiarrhythmic surgery has survived as a discipline in a decreasing number of experienced hands [43,44]. As a result of recent experiences and modern technology, success rates above 90% [74-76, 81,88] for the interventional treatment of congenital tachycardias have become comparable to those reported in patients with "normal" hearts. For acquired tachycardias, acute success rates today range about 80% at the atrial level. The rate of recurrence is still relatively high at about 10-25% [73,76,77,79,91,96,102]. Further improvements are being pursued. Data on the treatment of acquired tachycardias at the ventricular level is largely anecdotal. Good early success rates are combined with a tendency to recurrence in longer-term follow-up [50,76,103-108]. Some of the late VT ablation recurrences may be explained by the fact that fibrotic, scarred, and hypertrophic myocardial tissue at the targeted site often prevents effective radiofrequency current application and lesion generation. In order to improve RF lesion depth and continuity, newly designed technologies for radiofrequency current ("cooled tip electrode", Cordis Webster, Baldwin Park, CA), and alternative energy sources (cryo-ablation, micro-wave, or ultrasound) are being readied for introduction in the very near future. For patients suffering from recurrent tachycardias and having other reasons for open-heart surgery, a hybrid concept can be created, utilizing modern 3-D electro-anatomical reconstruction as a basis for an electrophysiologically informed surgical procedure. Following such a concept, a hemodynamic catheterization can be combined with an electrophysiologic study to define critical myocardial zones for induced macro-re-entry tachycardias, or of those zones expected to play an arrhythmogenic role in the future. With such information, surgical incisions for cardiac access and repair can be planned and performed. The role of surgery in antiarrhythmic treatment can become preventive. Myocardial tissue is incised for cannulation and repair in a way that can reduce the chance of later scar-associated tachycardias [109]. The extension of surgical cuts to physiologic barriers of electrical conduction is a major strategy for the primary prevention of postsurgical or incisional arrhythmias. In addition, the simultaneous treatment at heart surgery of already existing tachycardias can be offered within the same session as a secondary preventive concept. Despite the immense growth of knowledge and experience in recent years, there is still a need for more knowledge about the factors causing arrhythmogenesis and their interactions. Prospective and randomized studies are needed to show the most effective strategies to prevent arrhythmia-mediated death. The future of antiarrhythmic treatment will less be directed by the limitations of current interventional tools, which will be improved, and more by an evolutionary process in philosophy regarding the understanding of arrhythmogenesis in these patients as the basis for new concepts of arrhythmia prevention and treatment.