We present a case of a single chamber atrial pacemaker implanted for sinus node dysfunction and treatment of macroreentrant atrial tachycardias with atrial antitachycardia pacing. The patient presented with sustained atrial tachycardia above the detection rate, however, the device was unable to detect the tachycardia and did not deliver the programmed therapy. We discuss the nuances of the atrial tachyarrhythmia detection algorithms, and the programming strategies to maximize detection of atrial arrhythmias in a single chamber atrial pacemaker.