Trials of pacing to control ventricular rate during atrial fibrillation.

Pharmacologic therapy to achieve rate control in patients with atrial fibrillation is often difficult and inadequate. For this reason, ventricular pacing strategies have been developed as an alternative to drug therapy to alleviate symptoms due to rapid and irregular ventricular rates. Ventricular pacing in combination with AV junctional ablation provides palliative improvement in a wide range of clinical outcomes. Because of the irreversible complete AV block associated with this procedure, strategies to control the ventricular response to atrial fibrillation by ventricular pacing alone have been investigated. These strategies are primarily directed at regularizing the ventricular response by pacing at or near the mean intrinsically conducted ventricular rate. These specialized ventricular pacing algorithms provide striking ventricular regularity at rest but may be less effective during activity. No study has yet demonstrated clinically significant improvements in clinical outcomes with these algorithms. The clinical benefits of rate regularization alone without the strict rate control provided by AV junctional ablation are likely to be very limited. Other device based approaches to control ventricular rate in atrial fibrillation include transvenous vagal stimulation. This strategy is in early stages of development but may be promising.