Programmed Atrial Sensitivity: A Critical Determinant in Atrial Fibrillation Detection and Optimal Automatic Mode Switching

Abstract

Automatic mode switching (AMS) prevents tracking of paroxysmal atrial fibrillation (AF) in dual chamber pacing. The correct detection of AF can be affected by the programmed atrial sensitivity (AS). We prospectively studied the relationship between AS, AF undersensing, and AMS, using unfiltered bipolar intracardiac atrial electrograms recorded from 17 patients during sinus rhythm (SR) and in AF. Overall, 780 rhythms were recorded and replayed onto three dual chamber pacemaker models using different AMS algorithms (Thera DR 7940, Marathon DDDR 294-09, and Meta DDDR 1254), and the ventricular responses were measured. AS was randomly programmed in steps from the highest available AS to half of the mean atrial P wave amplitude (PWA), and the percentage of appropriate AMS responses (defined as a ventricular pacing rate at the expected AMS mode) were recorded. AMS efficacy was related to the programmed AS settings in an exponential manner. At low AS settings, a higher percentage of tests were associated with absence of, or with intermittent AMS and tracking of AF, whereas at higher AS, oversensing of noise during SR occurred. An optimal AS measured approximately 1.3 mV, representing about one-third of the PWA measured during SR, although oversensing of SR and undersensing of AF continued to occur in 14% of tests and time, respectively, due to the high variation in PWA during AF. Thus, a fixed AS cannot eliminate AF undersensing without inviting noise oversensing, suggesting the need for automatic adjustments of AS, or the use of a rate-limiting algorithm to prevent rate oscillation during intermittent AF sensing. In conclusion, AMS functions of existing pacemakers were significantly limited by the undersensing of AF and oversensing of noise. Proper adjustment of the AS is important to enable effective AMS during AF.

Understanding Atrial Fibrillation: The Signal Processing Contribution, Part II

“…Time domain parameters are widely applied, e.g., to evaluate the effect of drugs [35,36,37], exercise [35,38,39,40], and to predict outcome of cardioversion or invasive procedure results [41]. For example, SDNN showed a significant positive correlation with the exercise capacity and was the only independent predictor of normal exercise capacity [39] in patients with idiopathic AF.…”

“…For example, SDNN showed a significant positive correlation with the exercise capacity and was the only independent predictor of normal exercise capacity [39] in patients with idiopathic AF. Effects of various drugs have been tested by time domain parameters, showing expected drugs characteristics [36,37] as well as drug properties not commonly tested [35]. In particular, ECGs were recorded in a four-phase protocol (before and after infusion of flecainide, a commonly used antiarrhythmic drug, at rest and immediately after exercise) in order to characterize ventricular response to both exercise as autonomic nervous system (ANS) stimulus and flecainide which is also supposed to have effects on the ANS [35].…”

Mode-Switch-Algorithmen: Programmierbarkeit und Nutzen

“…Die Qualität der atrialen Wahrnehmung entscheidet über die Effektivität der Mode-Switch-Funktion [34]. Bei hochgradigem atrialen Undersensing wird Vorhofflimmern nicht erkannt und unregelmäßig und möglicherweise tachykard vom Schrittmacher auf den Ventrikel übergeleitet, was in beiden Fällen zu einer Verschlechterung der systolischen linksventrikulären Funktion führen kann.…”

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

“…Each of these strategies encounters its own problems. 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].…”