Atypical Form of the Fourth Criterion for Transient Entrainment

The typical fourth criterion for transient entrainment is defined when both a sudden shortening in conduction interval to and a distinct change in electrogram morphology at a bipolar recording site are demonstrated while performing overdrive pacing of a reentrant tachycardia from a single pacing site at two different constant rates. The purpose of this article was to test the hypothesis that if an intracardiac recording site showing both orthodromic and antidromic capture with entrainment pacing is located suitably distant from the circuit, sudden shortening in conduction interval to that site may occur without any significant change in the bipolar electrogram morphology (i.e., atypical form of the fourth criterion). Atrial overdrive pacing of orthodromic tachycardia was performed in 20 patients with either left anterior (12 patients) or left posterior (8 patients) accessory pathways. We investigated the effects of overdrive pacing from the proximal or distal coronary sinus, specifically effects on the electrogram interval and the electrogram morphology at the right atrial appendage. Overdrive pacing of orthodromic tachycardia from the proximal coronary sinus was performed in 10 of the 12 patients with left anterior accessory pathways; those 10 patients demonstrated the first entrainment criterion at the right atrial appendage site. Overdrive pacing of orthodromic tachycardia at still shorter cycle lengths demonstrated a sudden shortening in conduction interval to the right atrial appendage site. Despite shortening in conduction interval the morphology of the right atrial appendage electrogram was completely or almost identical to that during orthodromic tachycardia, indicating an atypical form of the fourth criterion. This criterion was not demonstrated in patients with left posterior accessory pathways. Thus, atypical fourth entrainment criterion was demonstrated during overdrive pacing of orthodromic tachycardia from the proximal coronary sinus only in patients with left anterior accessory path ways. Demonstration of atypical fourth criterion seems largely dependent on the location of the accessory pathway, the pacing, and the recording sites.     

Bifurcation properties of the two process model

Abstract Daan's two process model is known to be one of the most powerful models, covering various situations from free-running to sleep deprivation. In this study, bifurcation properties of the model dynamics as function of a gap, D , between the threshold processes are clarified using a circle map. As a function of D , we will show that the model has the different types of the mutual entrainment regions that are intervened by the tangent bifurcation. The variable behavior of human circadian rhythm is suggested to be systematically understood based on the bifurcation properties of the two process model.     

Control of the rat's circadian self-stimulation rhythm by light-dark cycles.

Rats with hypothalamic and septal electrodes were maintained in continuous test environments where bar-press responses produced brief reinforcing electrical stimulations. Long-term trends in response emission were measured under continuous exposure to light, dark and 12 hr light-dark alternations. In addition, transient behavioral adjustment to sudden 180 degrees phase shifts in the light-dark schedule was studied. The ambient light condition was found to control the period and phase of the circadian rhythm of brain self-stimulation behavior, as quantified by Fourier analysis. The circadian period was greatest under constant light (up to 24.90 hr under dim illumination), and approximated 24.00 hr under constant dark. Successful nocturnal entrainment to 12 hr light-dark alternations was obtained, with the peak of the 24 hr Fourier fundamental occurring in the middle-to-late dark segments. Three to 11 days were required for re-entrainment to 180 degrees light-dark phase shifts, during which the behavioral oscillation period increased to values comparable to periods under constant light. The rate of re-entrainment appeared to be proportional to illumination intensity during light segments.     

十字旋阀塔板的流体力学性能

在1 000 mm的圆塔内,采用空气-水系统对十字旋阀塔板的流体力学性能进行了测试,考察了液流强度、出口堰高、开孔率等因素对塔板压降、雾沫夹带及泄漏性能的影响。结果表明:在小液流强度下,十字旋阀塔板上气体分散均匀,泡沫层高度稳定,气液接触充分,具有较好的流体力学性能和优势。     

Future perspectives on neural mechanisms underlying rhythm and music based neurorehabilitation in Parkinson’s disease

Parkinson’s disease (PD) is characterized primarily by a dysfunctional basal ganglia (BG) system, producing motor and non-motor symptoms. A significant number of studies have demonstrated that rhythmic auditory stimulation can improve gait and other motor behaviors in PD that are not well managed by the conventional therapy. As music, being highly complex stimulus, can modulate brain activity/function in distributed areas of brain, the therapeutic properties of music potentially extend to alleviate non-motor symptoms of PD. Despite the clinical, behavioral evidence and promises of rhythm and music based interventions, the neural substrates underlying the effectiveness are poorly understood. The goal of this review is to appraise the current state of knowledge in order to direct further neuroimaging studies that help to determine the therapeutic effects of rhythm and music based interventions for motor and non-motor symptoms of PD.     

Sustained monomorphic ventricular tachycardia ablation from the aortic sinus of valsalva

INTRODUCTION: The aim of this study was to delineate the electrophysiologic mechanisms of a novel type of ventricular tachycardia (VT) originating from the aortic sinus of Valsalva. METHODS AND RESULTS: Endocardial mapping was performed in four patients with symptomatic VT originating from the aortic sinus of Valsalva. Two patients suffered from dilative cardiomyopathy; the other two patients had no structural heart disease. Five VTs could be induced and terminated by programmed ventricular stimulation. Successful ablation was performed in the noncoronary sinus of Valsalva in three VTs and in the left aortic sinus in two. Abnormal (diastolic or presystolic) potentials were recorded during sinus rhythm (mean interval from the end of QRS complex to the potential 121+/-98 msec) and during VT (mean interval from the potential to QRS complex 64+/-45 msec) at effective sites in the aortic sinuses of Valsalva. Concealed entrainment was demonstrated at all successful sites. VT recurred in one patient after 1 month, whereas no recurrences were observed during follow-up of 8+/-6 months in the other three patients. CONCLUSION: Reentry constitutes one mechanism of VT originating from the aortic sinus of Valsalva. Entrainment mapping is useful to characterize the reentrant circuit of these VTs and to guide ablation.     

Entrainment of reentrant tachycardia in a computer model

Capture of the cardiac rate by pacing followed by an immediate return to the original rate after pacing has been proposed as characteristic of reentrant rhythms. In this study, such entrainment has been demonstrated using computer-model simulations of propagated excitation and of reentry associated with structural and functional obstacles. With structural obstacles, the mechanism of entrainment was bidirectional propagation of paced excitation in reentry circuits, with collision of the reentrant and paced excitation in one direction and continued propagation of paced excitation in the other direction. The time of pacing onset, rate, and location all affected the QRS waveform during entrainment. With a particular time of onset and rate of pacing, the duration of time during which the QRS waveform underwent dynamic change was directly related to the distance between the pacing site and reentrant circuit. The location of reentry associated with functional obstacles moved so that the relationship between pacing-induced and reentrant excitation varied. In some cycles, pacing did not alter reentrant circuits, that is, entrainment did not occur, while other cycles were entrained, but by a different mechanism than that with structural obstacles. Leading circle reentry circuits, consisting of propagation away from and returning to reentry sites, did not have an excitable gap and paced excitation did not enter those circuits. Paced excitation did, however, enter the propagation paths between leading circle reentry circuits and modified the circuits by affecting the recovery of excitability.     

Electrophysiologic studies in atrial flutter

The clinical electrophysiologic approaches to atrial flutter (F) have been activation mapping and the observation of changes induced by programmed stimulation. Sequential endocardial activation mapping has recently yielded information indicating that common F is produced by a large right atrial (RA) reentry circuit, with counterclockwise rotation in the frontal plane, including the inferior vena cava in its center. Functional block in the crista terminalis and conduction slowing in the approaches to the atrioventricular node seem to be important to support reentry. F inscribing positive deflections in the inferior leads usually follows the same path, but in a clockwise direction. Atypical F may be produced by left atrial circuits. Atrial stimulation during F entrains the circuit, resetting it with each stimulus. Collision between antidromic and orthodromic activation during entrainment produces fusion that can be identified in the surface electrocardiogram. The last paced activation restarts F, unless circuit penetration has been enough to modify it by block or disorganization. Entrainment may result in F acceleration, with changes in activation sequence, suggesting a different type of reentry, possibly based on functional factors.