Atrial fibrillation: can it be cured by limited radiofrequency applications?

Atrial fibrillation is the most common sustained arrhythmia causing substan tial morbidity and probably increasing the risk of death. Most commonly, it is divided into a paroxysmal form, when - by definition - episodes end spo ntaneously, or a persistent one that lasts and requires a medical or electr ical intervention for its termination. It might be called permanent, when n o 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 p atients 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 co mpartimentation of both atria (MAZE procedure) is able to abolish atrial fi brillation in up to 90% of patients with chronic paroxysmal and also persis tent atrial fibrillation. However, all studies trying to imitate the MAZE p rocedure by electrophysiological catheter-based techniques applying radiofr equency energy to produce transmural linear lesions were either not success ful or showed a non-acceptable complication rate, especially a high rate of cerebrovascular accidents. The rationale behind the principle of compartim entation of the atria is the reduction of the critical atrial muscle mass n ecessary to facilitate fibrillation of the atria. A different approach aimi ng especially at the problem of paroxysmal atial fibrillation is based on t he observation that there might be a "focal trigger" responsible for the in itiation of the atrial tachyarrhythmia and that by eliminating this focal t rigger atrial fibrillation can be avoided. This hypothesis was first verifi ed in patients by Haissaguerre et al., in fact experimental creation of "fo cal atrial fibrillation" was presented by Moe and Abildskov more than 30 ye ars ago. During the last 3 years the concept of curing paroxysmal atrial fi brillation by applying focal radiofrequency lesions was supported by the re sults of several groups in more than 200 patients: 60 to 85% of patients ca n be cured, but in almost half of the cases more than one procedure is nece ssary. 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 suppor ted by surgical experience from performing pulmonary vein isolations during open heart surgery. Most recently, the concept of eliminating the trigger was extented and appl ied 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 i s the risk of the procedure well defined. Besides the necessity of performi ng a transseptal catheterization there is the risk of cardiac embolism and pulmonary vein stenosis. The endpoint of the procedure is also not well def ined: instead of trying to elimate the "trigger" located in a pulmonary vei n, it might be safer to isolate the "arrhythmogenic vein". This however, is a difficult task with current catheter technologies. It can be expected th at new catheter designs for mapping and ablation and - maybe - the use of a lternative energy sources - e.g., ultrasound, microwave - will make the pro cedure easier and applicable to more patients with drug refractory atrial f ibrillation.