A device, such as an implantable cardiac device, and method for switching between arrhythmia prevention modes is disclosed. The method includes monitoring an electrocardiogram (EGM) of the heart, determining whether the heart is in a normal sinus rhythm or in an abnormal rhythm, delivering pacing pulses at a first rate to either an atrium or a ventricle when the heart is in a normal sinus rhythm, and delivering pacing pulses to a ventricle at a second rate when the heart is in an abnormal rhythm, such as an atrial arrhythmia. The first rate is selected to minimize the occurrence of premature ventricular contractions, and the second rate is selected to both minimize the occurrence of premature ventricular contractions and minimize the occurrence of premature conducted beats.
