An example implantable medical device (IMD), such as an implantable cardioverter defibrillator, may be configured to store a ventricular tachycardia zone, wherein the ventricular tachycardia zone specifies ventricular depolarization rates indicative of ventricular tachycardia, and to deliver pacing pulses to at least one ventricle of a heart in response to detecting intrinsic atrial depolarizations at rates within the ventricular tachycardia zone. The IMD may further store a maximum ventricular tracking rate that is greater than a lower bound of the ventricular tachycardia zone, and be further configured to deliver the pacing pulses to the at least one ventricle in response to detecting intrinsic atrial depolarizations at rates up to the maximum ventricular rate. In this manner, the IMD may be configured with overlapping pacing and tachyarrhythmia detection zones. In some examples, the IMD dynamically modifies the maximum ventricular tracking rate for ventricular tracking pacing within the ventricular tachycardia zone.
