Implantable medical device having atrial tachyarrhythmia prevention therapy

An implantable medical device provides atrial arrhythmia prevention pacing when an interatrial conduction disturbance is detected. The implantable medical device includes a signal processor that detects the interatrial conduction disturbance and a pulse generator circuit coupled to the detector that delivers the atrial arrhythmia prevention pacing pulses to the heart when the processor detects the interatrial conduction disturbance. The interatrial conduction disturbance may be a P-wave duration, a difference between odd and even P-waves, or a predetermined P-wave spectral energy distribution.