The arrhythmia unhiding® function enables an adaptive refractory period to search for atrial arrhythmia hidden by ventricular pacing.

• the device increases the alert period to unmask a fast atrial cycle following ventricular pacing
• an adaptive relative refractory period is enabled when the ventricular pacing length is less than two times the longest tachycardia detection interval/rate or two times the pacing refractory period, whichever is shorter
• if a sensed event occurs in the adaptive relative refractory period and the next event is paced, then the adaptive relative refractory period is enabled again
• if no sensed event occurs in the adaptive relative refractory period or the next event is not paced, then the adaptive relative refractory period returns to normal
• once the number of intervals specified by Arrhythmia Unhiding® have occurred consecutively with a sensed event in the adaptive relative refractory period, the pacing cycle length is extended for 6 cycles in an attempt to reveal the arrhythmia