Automatic Mode Switching of Implantable Pacemakers: I. Principles of Instrumentation, Clinical, and Hemodynamic Considerations

Abstract

Automatic mode switching (AMS) is now a programmable function in most contemporary dual chamber pacemakers. Atrial tachyarrhythmias are detected when the sensed atrial rate exceeds a "rate-cutoff," "running average," "sensor-based physiological" rate, or using "complex" detection algorithms. AMS algorithms differ in their atrial tachyarrhythmia detection method, sensitivity, and specificity and, thus, respond differently to atrial tachyarrhythmia in terms of speed to the AMS onset, rate stability of the response, and speed to resynchronize to sinus rhythm. AMS is hemodynamically beneficial, and most patients with atrial tachyarrhythmias are symptomatically better with an AMS algorithm in their pacemakers. New diagnostic capabilities of pacemaker especially stored electrograms not only allow programming of the AMS function, but enable quantification of atrial fibrillation burden that facilitate clinical management of patients with implantable devices who have concomitant atrial tachyarrhythmia.

Pacemaker Timing Cycles and Special Features

“…Long programmed refractory periods should be avoided when rate-modulated pacing is enabled, since it could prevent appropriate sensing of rapid intrinsic events functioning inadvertently with an 15 The VVIR timing cycle consists of a lower rate limit (LRL), an upper rate limit (UR), and a ventricular refractory period (VRP, represented by blue triangles). As indicated by sensor activity, the V-V interval shortens accordingly (blue area represents the range of sensordriven VV interval).…”

“…14,15 The change in pacing mode occurs after specific criteria for atrial arrhythmia have been met. 14,15 The change in pacing mode occurs after specific criteria for atrial arrhythmia have been met.…”

Contemporary Pacemaker and Defibrillator Device Therapy

“…Automatic mode switching is, undoubtedly, one of the most useful and widely applied algorithms currently available; it provides for the detection of atrial tachyarrhythmias and conversion from dual-chamber to single-chamber ventricular pacing to preempt pacer-mediated tachycardia, with reversion to dual-chamber pacing once the sinus mechanism has reemerged 63,64 (Figure 8). Oversensing, which results in false-positive automatic mode-switching responses, may be observed, most commonly from far-field sensing of the end of the QRS complex by the atrial channel, especially in the setting of noise and low right atrial implants 63 (Figure 4).…”

“…Oversensing, which results in false-positive automatic mode-switching responses, may be observed, most commonly from far-field sensing of the end of the QRS complex by the atrial channel, especially in the setting of noise and low right atrial implants 63 (Figure 4). An analysis of automatic mode-switching episodes may provide the clinician with an estimate of the incidence of atrial dysrhythmias, prompting clinical decisions such as institution of anticoagulation, antiarrhythmic drug therapy, or even ablation; the above limitations of algorithm analysis regarding sensitivity and specificity must, however, be considered.…”

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.…”