Pacing to Prevent Atrial Fibrillation
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For some time it has been suggested that atrial pacing may prevent the development of atrial fibrillation. The perception is based on retrospective and prospective studies of patients with sinus node dysfunction in whom dual chamber pacing was compared to ventricular pacing. Ventricular pacing was associated with a significantly higher incidence of atrial fibrillation and CVA. Recently, the use of multi-site atrial pacing has been investigated to prevent atrial fibrillation in patients with a history of PAF. Daubert reported the prevention of atrial fibrillation in 12/12 patients at a mean F/U of 18 months utilizing right atrial appendage and coronary sinus pacing. Saksena reported on the use of high and low (near the ostium of the coronary sinus) right atrial pacing to acutely and chronically prevent atrial fibrillation. In 8/13 patients the induction of atrial fibrillation was prevented in the EP laboratory and in 14 patients dual site pacing reduced the recurrence rate from 2.01 to 0.39 episodes per week. Which patients will benefit from this approach and what the optimal location and method of pacing is has yet to be determined. Cheap generic Depakote

Atrial Defibrillation

The use of internal direct current shocks to electrically convert atrial fibrillation has recently been investigated. Bilateral energy delivery has been shown to significantly reduce the energy required to convert atrial fibrillation. This approach has been used to successfully cardiovert patients who had failed chemical or external direct current cardioversion.

Atrial fibrillation is usually divided into paroxysmal and chronic. Recently it has been suggested that persistent be included as a third classification. These patients have paroxysmal AF, however their episodes are not self limited and cardioversion is required to restore sinus rhythm. Eventually, attempts at restoring sinus rhythm are abandoned in these patients and they are classified as having chronic atrial fibrillation. Interestingly, it is now thought that atrial fibrillation produces chronic changes in atrial tissue and promotes the production and maintenance of AF. This concept of “afib begetting afib” was recently investigated by Wijffels. Clear electrophysiologic and structural changes occurred in an animal model of atrial fibrillation. Therefore, early cardioversion (minutes to hours) may lessen the tendency to arrhythmia recurrence and the development of chronic atrial fibrillation. This has led to the development of an implantable atrial defibrillator. The advantages of such a device would be: the avoidance of potentially toxic medications, reduction of embolic risk and obviate the need for repeated hospitalizations. In addition, it may decrease the incidence of atrial fibrillation by preventing the structure and electrophysiologic changes in the atrium. Questions yet to be answered concern the safety, clinical utility, tolerability, and cost effectiveness of such a device. Human trials are now underway in Europe and soon to start in the US. Clinical trials of an atrial defibrillator have been ongoing in Europe and recently begun in the United States. Over 100 devices have now been implanted without any proarrhythmia and with fair patient satisfaction.