In a study of the
In a study of the atrial pacing preference (APP) algorithm, Ogawa et al.  randomly programmed pacemakers as APP OFF and APP ON at 3 different settings (8, 16, and 33 cycles). The authors found that the most effective setting differed according to the patient and thus concluded that this therapy necessitated the determination of the “optimal” setting for each patient. The efficacy of any atrial pacing algorithm depends on background factors such as hypertension, diabetes, and any other condition that could promote tissue fibrosis. Furthermore, the effect of the algorithm is influenced by programming options such as the atrioventricular delay, the pacing rate, and the number of pacing cycles. Garrigue et al.  used programmed increases in the lower rate from 55ppm to 72ppm, along with increases in the atrial pacing rate from 32% to 67%, to achieve significant reductions in the number and duration of paroxysmal AF episodes. That trial demonstrated that a relatively high atrial pacing rate might be necessary to inhibit the AF triggers and that it would also be necessary to set the Sirtinol rate according to the tolerance of each patient.
The ventricular pacing rates differed greatly among the trials (from 11% to 93%). Interestingly, the ventricular pacing rate was not associated with the effectiveness of AF suppression. In a randomized trial, Gold et al.  demonstrated a reduction in the AF burden with a right ventricular pacing rate of 96%. However, these ventricular pacing data do not agree with other reported evidence suggesting that ventricular pacing is inferior to atrial pacing for reducing the incidence of AF. Overall, atrial pacing appears to play a more important role than ventricular pacing in this setting. Most trials had a relatively short follow-up period and did not produce consistent results.
An interesting finding of the Study for Atrial Fibrillation Reduction (SAFARI) trial was that the AF reduction benefit was greater among patients with a high baseline AF burden than among those with a relatively low baseline AF burden . This finding might possibly explain why a subsequent large trial  failed to confirm the efficacy of an AF suppression algorithm in patients with no history of AF. That very large randomized study of 2343 patients without a history of AF reported that continuous atrial overdrive pacing did not prevent new-onset AF, was poorly tolerated, and accelerated pulse generator battery depletion. Data from the trial with the longest follow-up period  revealed that AF prevention pacing was effective for at least 66 months in more than 50% of the study patients (Fig. 3). An overall assessment of the long-term effects of AF prevention pacing is difficult to conduct because the general conditions of the patients and their surrounding circumstances vary on a case-by-case basis because of aging, blood pressure, and many other factors. AF mechanisms such as the PAC trigger might also influence the responses to pacing-based AF suppression therapies.
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Introduction The atrial high rate episode (AHRE) diagnostic function of implantable cardiac devices is often used to detect atrial tachyarrhythmias (ATA). However, its reliability and characteristics vary, depending on the device settings and use of other functions, such as the rate-adaptive mode or the atrial overdrive pacing (AOP) algorithm, especially in dual-chamber devices. The “ASymptomatic atrial fibrillation and Stroke Evaluation in pacemaker patients and the atrial fibrillation Reduction atrial pacing Trial” (ASSERT) examined the impact of device-detected, subclinical ATA on the development of strokes and systemic embolisms [1,2]. In that study, the presence of subclinical ATA was associated with a significant 2.5-fold higher risk of thromboembolic events in pacemaker or ICD recipients . The diagnosis of subclinical ATA based on the presence of AHRE is critical information that should prompt the initiation of appropriate preventive therapies, such as long-term oral anticoagulation or antiarrhythmic medications.