From MAZE to ICE: new concepts and new technologies for surgical ablation of atrial fibrillation

Curative treatment strategies for patients with atrial fibrillation were introduced in the late 1980s by Cox and co-coworkers.1 Following extensive animal experimental studies, the Maze procedure was developed and applied clinically. Subsequently, modifications of the initial surgical strategy were introduced, i.e. the Maze II and Maze III procedure.2,3 The efficacy of the Maze operation to establish permanent and stable sinus rhythm in >90% of patients treated was impressive.4 For a long time, the Maze III was cited as the ‘gold standard’ for the curative treatment of atrial fibrillation, but the extensive and time-consuming nature of this ‘cut and sew’ procedure prevented its widespread use. However, the curative potential of the Maze operation was recognized and inspired interventional electrophysiologists to attempt to reproduce the Maze procedure by means of transcatheter ablation techniques. Although never published as a full manuscript, the pioneering studies performed by John Swartz which were based on the Maze concept actually opened a new window for interventional electrophysiology, i.e. the development of catheter ablation of atrial fibrillation. Thus, the roots of curative treatment of atrial fibrillation clearly go back to cardiac surgery and it is unlikely that catheter interventional techniques would have made such significant progress without this initial ignition from the surgical theatre. In the late 1990s, the first surgical modifications of the classical Maze operation using radiofrequency energy were developed. Some of these concepts aimed at the partial or complete reproduction of the Maze III lesion line concept while others introduced new treatment strategies based on the growing pathophysiological understanding of atrial fibrillation.5–7 Subsequently, new energy sources such as microwave, cryoenergy, and highly focused ultrasound were introduced to facilitate lesion induction in the atria during cardiac surgery. Recently, Khargi and co-workers published a meta-analysis of a large number of studies reporting the results of surgical ablation of atrial fibrillation using various energy sources for ablation compared with the results of the classical Maze procedure.8 In that meta-analysis, ablation of atrial fibrillation using ablation energy sources proved to be as effective as the classical Maze operation. Today, the approach most frequently applied for the surgical treatment of atrial fibrillation aims for the induction of contiguous circumferential isolating lesions around the pulmonary veins using radiofrequency, cryoenergy, or microwaves as the energy source. In these operations, ablative energy is delivered to the endocardial aspect of the left atrium during cardiopulmonary bypass. Surgical atrial fibrillation ablation procedures are currently widely used in an increasing number of institutions; however, it seems that indications, treatment concepts, treatment end-points, follow-up strategies, and electrophysiological expertise during follow-up are very inhomogeneous and may not always meet acceptable standards.