Mode switching failure during atrial flutter: the '2:1 lock-in' phenomenon

Abstract

'2:1 lock-in' is a typical form of MS failure in patients with atrial flutter and the mechanism is closely linked to the typical atrial sensing windows.

Use of an Atrial Lead with Very Short Tip-To-Ring Spacing Avoids Oversensing of Far-Field R-Wave

“…The use of atrial leads with a very short tip-to-ring spacing provides several benefits to clinical practice: 1) an effective reduction of inappropriate mode switch due to FFS, 2) a time saving in follow-up visits as no more individual adjustments of the PVAB is needed and 3) a possible lowering of the likelihood of 2∶1 lock-in of atrial flutter [15] by the application of short PVAB intervals (median 60 ms versus 128 ms).…”

“…Reducing the atrial sensitivity runs the risk of undersensing during atrial tachyarrhythmias [13], [14] and can therefore end in an underestimation of the atrial tachyarrhythmia burden. Adjusting the PVAB – although highly effective in avoiding inappropriate mode switch [8], [10]–[12] – encounters some extra time for individual optimization of the parameter in follow-up visits and it is not devoid of tachyarrhythmia misclassification as a 2∶1 lock-in of atrial signals may occur with atrial flutter [15].…”

Diagnostic tools for atrial tachyarrhythmias in implantable pacemakers: a review of technical options and pitfalls

“…This event is defined as the '2:1 lock-in phenomenon' ( figure 6A and B). 34 PVAB to prevent FFRW sensing also prevents the sensing of every second atrial beat, causing the 2:1 lock-in phenomenon during the atrial tachycardia, resulting in a high ventricular paced rate when normal AV conduction is not present. During atrial tachycardia a mode switch will not occur due to this mechanism, if the upper rate limit is programmed at a higher rate than half of the AT/AFL rate.…”

Different Automatic Mode Switching in DDDR Pacemakers

“…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.…”