Modulate pacing rate to increase the percentage of effective ventricular capture during atrial fibrillation

An apparatus for determining whether ventricular pacing stimuli are capturing a paced ventricle during atrial fibrillation, comprising:

• processing means for determining whether a patient is experiencing atrial fibrillation;
• delivering means for delivering the ventricular pacing stimuli in response to determining the patient is in atrial fibrillation;
• sensing means for sensing signals in response to the ventricular pacing stimuli;
• processing means for determining whether the ventricular pacing stimuli are effectively capturing the paced ventricle over a series of the delivered ventricular pacing stimuli, the determination of whether the ventricular pacing are effectively capturing the paced ventricle comprising determining a number of consecutive ones of the series that effectively capture the paced ventricle;
• and
• modifying means for modifying a pacing rate during atrial fibrillation in response to the determination of effective capture by the ventricular pacing stimuli delivered during the series;
• wherein the modification to the pacing rate is based upon the determined number of consecutive ones of the series that effectively captured the paced ventricle.