Diagnosis of Supraventricular Tachyarrhythmias by Automatic Mode Switching Algorithms of Mode Switching Algorithms of Dual Chamber Pacemakers

Mode Switching of Dual Chamber Pacemakers from Activation of a Blanked Flutter Search Algorithm by a Single Atrial Event

“…> atrial cycle length, the pacemaker will exhibit 2:1 atrial sensing (or the 2:1 lock-in response) provided the unblanked AV interval < atrial flutter cycle. 2,6 The latter applies to Medtronic devices where substantial shortening of the sensed AV interval (minimum 30 ms) occurs with increasing sensed atrial rates. This response optimizes sensing of atrial flutter by the primary algorithm, and yet preserves a physiologic AV interval at rest and low levels of exercise.…”

“…1). 2,3 We have observed activation of this special algorithm in circumstances unrelated to atrial flutter, atrial tachycardia, or sinus tachycardia. This report describes 5 such cases involving AMS initiated by a single atrial event.…”

“…In this example, every second atrial flutter wave is not sensed by the pacemaker due to coincidence with the postventricular atrial blanking period (PVAB, black boxes in MD). However, if atrial cycles are sensed at an interval shorter than twice (AV delay + PVAB) and shorter than twice the tachycardia detection interval (corresponding to the rate at which the mode switching algorithm is activated) for eight consecutive cycles (annotations [1][2][3][4][5][6][7][8], the pacemaker suspects blanked atrial flutter. The Blanked Flutter Search (algorithm now extends the postventricular atrial refractory period (PVARP, white boxes in MD) for one cycle (arrow).…”

Different Automatic Mode Switching in DDDR Pacemakers

“…Third, inappropriate reversion to a tracking mode despite persistence of an atrial arrhythmia may also be caused by intermittent undersensing of the atrial electrocardiogram. Fourth, an overly sensitive mode-switching algorithm may result in loss of atrio-ventricular (AV) synchrony in sinus rhythm [2,11,17,19]. Finally, intrinsic AV conduction of an atrial arrhythmia may produce symptoms that are unrelated to the pacemaker [21].…”

“…Mode-switching algorithms are designed to alleviate symptoms related to tracking of atrial arrhythmias, that may result in inappropriately rapid or irregular ventricular pacing [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The ideal mode-switching algorithm should discriminate sinus tachycardia, a rhythm that should be tracked, from pathological atrial arrhythmias, rhythms that generally should not be tracked.…”