Diagnostics and Effectiveness of Prevention Pacing Therapy--论文代写范文精选

招收15例病人,进行先进房室传导干扰。我们比较的数量和持续时间，房颤发作的存储设备与24小时动态心电监测。之后,我们打开了心房心律失常的检测算法,从一个心房率每分钟超过180次。之后,为了评估可能减少的数量,我们定制了所有四个节奏预防算法。下面的essay代写范文将进行详述。

Introduction
Atrial fibrillation (AF), the most common and rising disorder of cardiac rhythm, is quite difficult to control and/or to treat. Non pharmacological therapies for AF may involve the use of dedicated pacing algorithms to detect and prevent atrial arrhythmia that could be a trigger for AF onset. Selection 900E/AF2.0 Vitatron DDDRP pacemaker (1) keeps an atrial arrhythmia diary thus providing detailed onset reports of arrhythmias of interest, (2) provides us data about the number of premature atrial contractions (PACs) and (3) plots heart rate in the 5 minutes preceding the detection of an atrial arrhythmia. Moreover, this device applies four dedicated pacing therapies to reduce the incidence of atrial arrhythmia and AF events.Aim of the Study. To analyze the reliability to record atrial arrhythmias and evaluate effectiveness of its AF preventive pacing therapies.

Material and Methods. We enrolled 15 patients (9 males and 6 females, mean age of 71±5 years, NYHA class I–II), with a DDDRP pacemaker implanted for a “bradycardia–tachycardia” syndrome, with advanced atrioventricular conduction disturbances. We compared the number and duration of AF episodes’ stored in the device with a contemporaneous 24h Holter monitoring. After that, we switched on the atrial arrhythmias detecting algorithms, starting from an atrial rate over 180 beats per minute for at least 6 ventricular cycles, and ending with at least 10 ventricular cycles in sinus rhythm. Thereafter, in order to evaluate the possible reduction in PACs number and in number and duration of AF episodes, we tailored all the four pacing preventive algorithms. Patients were followed for 24±8 months (from 20 to 32 months).

Results. All 59 atrial arrhythmia episodes occurred in the first part of this trial, were correctly recorded by both systems, with a correlation coefficient (r) of 0.96. During the follow–up, we observed a significant reduction not only in PACs number (from 83±12/day to 2.3±0.8/day) but also in AF episodes (from 46±7/day to 0.12±0.03/day) and AF burden (from 93%±6% to 0.3%±0.06%). An increase in atrial pacing percentages (from 3%±0.5% to 97%±3%) was also contemporaneously observed.

Discussion and Conclusion
Presently, very few clinical randomised trials29–32 have compared the overlapping between pacemaker stored data and Holter monitoring ones, so that there is not a significant evidence of data about the reliability of these devices in properly recognising and monitoring supraventricular tachyarrhythmias. It’s also well known that bipolar leads often are not enough able to discriminate ventricular far field from normal P-wave amplitude or from wavelets of AF. An Atrial Blanking feature, long enough, may completely mask this phenomenon, but it also represents a blind interval for the atrial channel, sometimes subsequently resulting in a possible negative effect for an optimal arrhythmia detection. Recently, Nicotra33 carried out a method for atria l sensing and blanking programming in order of guarantee reliable diagnostics in patients with paroxysmal AF. They proposed a decisional flow-chart based on the scanning of ventricular far field timing and amplitude that could focus and quantify this phenomenon for every kind of implanted device (Fig. 3). This approach was also used in the present study during the follow–up.

Our data confirm the significant reliability of Selection™ 900E/AF2.0 Vitatron® algorithms for detecting and monitoring AF. Moreover, we recorded a significant number of supraventricular tachyarrhythmia’s episodes, thus making stronger the statistical reliability of these data. Subsequently, we detected a progressive and significant reduction in AF burden and episodes. This decreasing in AF episodes and burden may be mainly related to the increase of atrial pacing, obtained by using a newly designed pacing overdrive algorithm responsible of atrial ectopic beats’ suppression in keeping with several trials11–28.

Most of the discussed trials showed a lower reduction in AF episodes and burden if compared with our study (AF burden decreasing from 85% to 35% vs. a reduction from 93% to 0.3%; p<0.001; 95% confidence interval: –9.253 to –6.747). As showed in our recordings, the exceeding share of AF episodes and AF burden reduction is more likely to be entrusted to the newly designed four preventive pacing algorithms stored in the tested device (Selection® 900E/AF2.0® Vitatron™ pacemaker). Alternatively, as the data shown in fig. 2 seems to underline, i.e. that the efficacy of pacing for reducing AF episodes/day was evident after only six months of treatment, may suggest that also atrial remodelling could play a role. Electrical, mechanical and anatomical remodelling indicate structural alterations that, once established, may vanish any attempt to restore sinus rhythm. Atrial fibrosis is probably the most critical factor of the remodelling process and appears to be largely media ted by several mechanisms. 

Our clinical data indicate that these non pharmacological interventions may reduce, in a roundabout way, AF burden and episodes, probably interfering also with someone of those electrical and structural remodelling processes. It is possible, however, that having a very few patients, although followed for a median time of 24 months, we have overestimated the general possible reduction in AF episodes and burden because of a strong selection of our patients. In particular, we selected our patients on the basis of their atrial tachyarrhythmias’ onset mechanisms, and we tailored the available preventive pacing algorithms in each patient on the basis of each onset. This tailoring of pacing preventive algorithms on the basis of the different onsets in each patient, associated with the well known anti–remodelling effect of atrial overdrive pacing on atrial refractoriness dispersion, was the more important goal of our study and the likely reason of the observed marked reduction in AF episodes and burden. Therefore, these examined pacing algorithms may represent an effective therapeutical options to contrast the nearly inevitable progression of this arrhythmia towards its permanent form.

The AF antiarrhythmic drugs therapy represents the first and more effective therapy, although it is well known that it is not always effective and free from side effects. In our patients, implanted for a sick sinus syndrome and at least partially resistant to AF pharmacological treatment, new interventional non–pharmacological solutions, such as tailored antiarrhythmic pacing algorithms, may represent a further effective therapeutical option. Recent analysis of AFFIRM33 and RACE trial34 showed that, in patients older than 65 years, with well defined risk factors, a therapeutical strategy based on ventricular rate control is not inferior to a strategy of maintaining sinus rhythm (rhythm control). However, this issue is still debated. Indeed, other clinical trials and sub–analysis35–40 showed that sinus rhythm restoration has to be preferred compared to rhythm control.

In conclusion, our experience suggests the reliability of well tailored pacing algorithms on AF control in selected patients with brady-tachy syndrome, refractory to pharmacological rhythm control. However, we should say that this study is partially limited by the small and highly selected sample used, that reduces the possibility of translating theses results to general population. Moreover, this was not a truly randomized, controlled study, and so interpretation of the clinical significance of the reduction of AF episodes, as also shown however by several other trials in International Literature, is uncertain, thus not allowing us for making really definitive conclusions. The main information, however, we can derive from this trial is that we should better evaluate, before every pacemaker implantation, the different AF onsets of each patient eligible for such a procedure, because only a really profound knowledge of the different onset mechanisms of atrial tachyarrhythmias in each subject may give us the possibility of choosing a really effective implantable device for these sometimes very different patients, thus obtaining the maximum effective clinical results from these pacing algorithms in terms of reduction of AF episodes and burden.（essay代写)

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