Various embodiments can reduce mode switching in response to inappropriate but anticipated signals, such as far field R-waves. Additionally, various embodiments can also increase the alert period for detection of true atrial tachyarrhythmias in dual chamber pacing systems. Further, various embodiments can reduce mode switching or tachyarrhythmia response to same chamber delayed signals. In addition, various embodiments can increase the alert period for detection of true tachyarrhythmias in multisite pacing systems arising from the chamber being stimulated or sensed while minimizing repeated detection and counting of the same native depolarization or evoked response to effectively preclude mislabeling and detection of a normal rhythm as a tachycardia.