Ivabradine for Rate Control in Permanent Atrial Fibrillation

Ivabradine may be useful as a rate controlling agent in atrial fibrillation without negative effects on hemodynamics and inotropy. The objective in this proof of concept study is to investigate the hypothesis that ivabradine will slow the ventricular response in patients with permanent atrial fibrillation and previously-implanted pacemakers.

In a simple cross-over study, the investigators will evaluate the impact of oral Ivabradine on exercise treadmill test, percent pacing as stored in pacemaker diagnostics, and 6 minute walk test. Aim/Hypotheses • To determine if the addition of Ivabradine to baseline cardiac medications slows mean and maximum heart rates in permanent atrial fibrillation Ivabradine will lower mean and maximum heart rates on treadmill exercise test, without lowering blood pressure Ivabradine will increase percent pacing, and lower rates over time as shown on pacemaker diagnostic data Ivabradine will improve exertional symptoms and exercise tolerance due to atrial fibrillation as measured by the Borg's scale during a six-minute walk test. Study Design Patients with permanent atrial fibrillation will undergo baseline exercise treadmill test, measurement of heart rates and percent pacing from pacemaker diagnostics, and a 6 minute walk test with symptomatic assessment of dyspnea using the Borg's scale score. Oral Ivabradine will be started at 5 mg twice daily, and up-titrated to a maximum dose of 7.5 mg twice daily at 7 days if percent pacing has not increased significantly or rates have not slowed more than 20bpm. Exercise treadmill test, measurement of heart rates and percent pacing from pacemaker diagnostics, and a 6 minute walk test with symptomatic assessment of dyspnea using the Borg's scale score will be repeated at 2 weeks.

Patients with permanent atrial fibrillation and previously implanted pacemakers who will be started on ivabradine.

Ivabradine will be started and titrated to heart rate slowing of 20 bpm or greater, or an increase in pacing.

Average ventricular heart rate will be recorded after the patient exercises on a treadmill using a heart rate monitor

Patients will undergo a 6 minute walk test, and symptoms and distance walked as measured by standard 6 minute walk protocol

Blood pressures will be monitored using a blood pressure cuff with the patient at rest for 10 minutes

Inclusion Criteria: Patients with stable blood pressures with permanent atrial fibrillation and implanted pacemaker pacing less than 50% of the time, with or without concomitant beta blocker or calcium channel blocker use Exclusion Criteria: Patients with uncontrolled hypertension will be excluded To eliminate confounding effects, patients on Digoxin therapy will be excluded Patients on anti-arrhythmic therapy Patients with pre-excitation on EKG Patients who pace > 50% of the time Patients with severe Child-Pugh C hepatic impairment