On the other hand it has been reported that

On the other hand, it has been reported that the Purkinje network can survive in patients with ischemic or idiopathic cardiomyopathy [6], and in patients with SB-334867 free base failure and left bundle branch block (LBBB). In addition, idiopathic LV tachycardia that involves the Purkinje network as the circuit is characterized as showing a narrow QRS [7]. Therefore, it is conceivable that direct pacing of the Purkinje fiber or Purkinje network may show a narrow QRS, comparable to conventional BiV pacing in favor of shorter QRS duration, and lead to impulse conduction in the LV endocardium in patients with advanced heart failure. Furthermore, Purkinje fibers are widely distributed in the LV and are easy to detect. We believe that PP pacing is superior to other LV endocardial pacing in reproducibility and ability to detect the Purkinje fiber as the pacing site, even in injured myocardium, but there has been no report of direct pacing of the Purkinje network.
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Acknowledgments
Introduction Atrial fibrillation (AF) occurs when atrial conduction converts from normal signal propagation to multiple reentering wavelets. On the electrocardiogram (ECG), the P wave reflects atrial depolarization and the indices provide information as to whether atrial depolarization usually occurs [1]. We previously reported that marked left atrial overload represented by a negative terminal portion of the P wave in lead V1 was associated with an increased risk of AF development [2]. In contrast, a biphasic P wave in the inferior leads was associated with delayed atrial conduction of Bachmann׳s bundle [3] and circling impulse propagation from the lower right atrium to the left atrium [4]. Therefore, both slow and anisotropic conduction could play a significant role in generating a biphasic P wave in inferior leads. In addition, these electrophysiological abnormalities could increase the tendency of reentry degenerating into AF. However, as to whether a biphasic P wave in the inferior leads is clinically associated with the development of AF is yet unknown. In this study, we investigated the following: (1) the association between a biphasic P wave in lead II with the development of AF and (2) the P wave characteristics in the inferior leads that may be associated with the development of AF.
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Results
Discussion The major findings of this study were as follows: (1) patients with a biphasic P wave in lead II had an increased propensity toward the occurrence of AF and a subsequent high rate of incidence and (2) the duration of the initial P wave portion in lead III was independently associated with the development of AF. The incidence of AF observed in the present study was much higher than that of a previous study in the general Japanese population [5] (234.7/1000 patient-years vs. 9.3/1000 patient-years).
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Acknowledgments
Introduction Complex fractionated atrial electrograms (CFAEs) derived from time domain analysis and dominant frequency (DF) identified by fast Fourier transform (FFT) spectral analysis are widely used electrical parameters for understanding the initiation and perpetuation of atrial fibrillation (AF) [1–7]. CFAEs are now considered to reflect simply (1) dyssynchronous activation of separate cell groups at pivot points, (2) wave collision, far-field potentials, (3) critical zones of repetitive activations of AF driver(s), or (4) local reentry circuits [1–5], whereas high DF is reported to be related to the center of a focal-firing rotor or local reentry circuit [6,7]. Clinically, CFAE and/or high-DF sites have been demonstrated as effective targets for AF termination, suggesting their importance in the maintenance of AF [1–7]. Nonetheless, the pathogenesis of CFAE and DF are not fully understood. Adenosine triphosphate (ATP) is known to promote AF by shortening the atrial action potential duration and refractory period [8–10]. In patients with paroxysmal AF (PAF), ATP infusion increases DF, particularly at the pulmonary vein (PV)–left atrial (LA) junction. DF is higher in patients with persistent AF (PerAF) than in patients with PAF at all the LA regions surveyed, but the extent of the DF increase with ATP is less in PerAF patients than that in PAF patients. Our preliminary results suggest that the ability of ATP to highlight sites driving PAF that could be targeted for ablation, whereas non-PV locations are more likely. Jadidi et al. reported [11] that atrial fibrosis as defined by delayed enhanced magnetic resonance imaging is associated with slower and organized electrical activity but lower voltage than healthy atrial sites in patients with long-lasting PerAF. Therefore, PerAF patients in the present study may represent electrical remodeling as demonstrated by higher DF and structural remodeling as shown by lower responses to ATP infusion, possibly due to patchy fibrosis around higher DF sites. In such cases, PV isolation plus LA ablation targeted at rotors in the LA body might be necessary. We therefore hypothesized that ATP may spatially affect the atrial electrogram interval determined by time domain and frequency domain analyses during AF. We investigated the effects of ATP on the atrial electrogram interval and DF characteristics in human AF, and evaluated whether these effects are influenced by the progression of atrial remodeling.