[Atrial fibrillation: healing by focal high frequency catheter ablation?]

Atrial fibrillation is the most common sustained arrhythmia causing substantial morbidity and probably increasing the risk of death. Most commonly, it is divided into a paroxysmal form, when--by definition--episodes end spontaneously, or a persistent one that lasts and requires a medical or electrical intervention for its termination. It might be called permanent, when no further attempts seem to be indicated for its elimination. Until recently, therapeutic strategies aimed at preventing cardiac embolism and at restoring and maintaining sinus rhythm by antiarrhythmic drugs. Long-term efficacy of the latter approach is poor, since less than 50% of patients can be maintained in stable sinus rhythm when periods of more than 1 year are considered. Can atrial fibrillation be cured? More than ten years ago Cox and coworkers demonstrated that the surgical compartimentation of both atria (MAZE procedure) is able to abolish atrial fibrillation in up to 90% of patients with chronic paroxysmal and also persistent atrial fibrillation. However, all studies trying to imitate the MAZE procedure by electrophysiological catheter-based techniques applying radiofrequency energy to produce transmural linear lesions were either not successful or showed a non-acceptable complication rate, especially a high rate of cerebrovascular accidents. The rationale behind the principle of compartimentation of the atria is the reduction of the critical atrial muscle mass necessary to facilitate fibrillation of the atria. A different approach aiming especially at the problem of paroxysmal atial fibrillation is based on the observation that there might be a "focal trigger" responsible for the initiation of the atrial tachyarrhythmia and that by eliminating this focal trigger atrial fibrillation can be avoided. This hypothesis was first verified in patients by Haïssaguerre et al., in fact experimental creation of "focal atrial fibrillation" was presented by Moe and Abildskov more than 30 years ago. During the last 3 years the concept of curing paroxysmal atrial fibrillation by applying focal radiofrequency lesions was supported by the results of several groups in more than 200 patients: 60 to 85% of patients can be cured, but in almost half of the cases more than one procedure is necessary. Most interestingly--and this is a finding of all investigators--more than 90% of the triggering ectopic foci are located in the pulmonary veins or in the pulmonary vein/left atrial junction. This concept is also supported by surgical experience from performing pulmonary vein isolations during open heart surgery. Most recently, the concept of eliminating the trigger was extended and applied to patients with established persistent atrial fibrillation. Until now, it has not been well established how many patients with paroxysmal atrial fibrillation are "good candidates" for a focal RF ablation procedure, nor is the risk of the procedure well defined. Besides the necessity of performing a transseptal catheterization there is the risk of cardiac embolism and pulmonary vein stenosis. The endpoint of the procedure is also not well defined: instead of trying to eliminate the "trigger" located in a pulmonary vein, it might be safer to isolate the "arrhythmogenic vein". This however, is a difficult task with current catheter technologies. It can be expected that new catheter designs for mapping and ablation and--maybe--the use of alternative energy sources--e.g., ultrasound, microwave--will make the procedure easier and applicable to more patients with drug refractory atrial fibrillation.