Sick Sinus Syndrome: Experience of a Cardiac Pacemaker Clinic

Out of a pacemaker clinic population of 182 patients 21 (11·5%) were found to have the sick sinus syndrome. Their ages ranged from 30 to 80 years and averaged 62. Ischaemic heart disease was more commonly an aetiological factor than in patients with chronic atrioventricular heart block. Other aetiologies were familial cardiomyopathy, postcardiac surgery, and dystrophia myotonica.Cardioversion before pacemaker insertion was a hazardous procedure. After insertion the occurrence of tachycardias and the need for drug therapy were reduced. One patient no longer required a pacemaker once atrial fibrillation became established.A high incidence of cerebral embolization was observed and the use of anticoagulant drugs therefore merits serious consideration.Failure of inhibition of demand-type pacemakers occurred in two patients. Two patients who exhibited competition with fixed-rate pacemakers died. Two patients were treated with electrodes surgically implanted on the right atrium. It is suggested that fixed-rate pacemakers may be contra-indicated and that sequential atrioventricular demand pacing is theoretically ideal.     

Does the presence of a human tracker affect the behaviour of radio‐tagged wood mice Apodemus sylvaticus?

1. While the effect on animals of handling them and fitting them with radio tags has been investigated, little work has been reported testing the effect of the presence of a human observer tracking an animal. 2. The activity of wood mice fitted with radio collars and confined to a semifield pen was measured in the presence and the absence of a human observer. Free‐ranging wood mice were radio tracked by using two protocols: ‘fixes’ taken periodically, and periods of continuous tracking. 3. There was no significant difference in any quantified aspect of the animals’ behaviour. This suggests that the presence of a human tracker has a negligible effect on the behaviour of wood mice.     

Permanent pacemaker malfunction: diagnostic aspects of temporary pacing.

A temporary pacing electrode can function as a diagnostic as well as a therapeutic tool. This is illustrated in two patients whose permanent pacemakers unexpectedly failed. In the first patient a demand pacemaker was inhibited by a magnet rather than converting to the asynchronous mode. In the second the pacemaker appeared to be producing low-voltage potentials not detectable on the surface electrocardiogram. The presence of a temporary pacing electrode can be useful for defining the cause of pacemaker failure and the nature of any associated arrhythmias.     

Tilt-table testing of patients with pacemaker and recurrent syncope

The diagnosis of recurrent syncope in patients with pacemakers (PM) is quite challenging and the etiology of syncope is often multifactorial. To portray the mechanism of syncope in PM patients, we report the results of head-up tilt table testing (HUT) in a series of patients with PM, originally implanted for reasons other than neurally mediated syncope, referred due to syncope or pre-syncope (aborted syncope, vertigo, suspected orthostatic hypotension).Forty-one patients with PM undergoing a HUT in our syncope unit between January 1st, 2007 and December 31st 2011 were included. A standard HUT protocol with nitroglycerine provocation was used and the test results were classified according to current guidelines. Baseline data were retrieved from the medical records.Overall, 54% of patients had a positive response to HUT. Vasodepressor or orthostatic hypotensive response were the most prevalent responses accounting for 72% of patients with a positive test. There were no differences between groups with positive or negative test result regarding age, gender, resting blood pressure and heart rate, daily fluid intake, pacing mode, pacing indication or pacing rhythm at rest.HUT in patients with pacemakers has a high diagnostic yield. Although, the majority of patients had a vasodepressor or orthostatic hypotensive response, cardioinhibitory response leading to syncope was also seen.     

Three Years' Experience with Implanted Pacemakers

At the University Hospital, Saskatoon, over the last three years, pacemakers have been inserted in 40 patients with complete or incomplete heart block. Fourteen of the patients were females and 26 were males. The average age was 65 years; 12 were over 80 years of age, and the youngest patient was 8 years of age. In none was the heart block due to operation. Thirty-three patients are still alive and well. There have been seven deaths three early and four late. One patient died because of a “runaway” pacemaker, and two as a result of infection persisting around the pacemaker. Twenty-nine Medtronic pacemakers were used and 14 Atricor pacemakers; currently we favour the latter instrument.     

Ocular clocks are tightly coupled and act as pacemakers in the circadian system of Japanese quail

Our previous studies showed that the eyes of Japanese quail contain a biological clock that drives a daily rhythm of melatonin synthesis. Furthermore, we hypothesized that these ocular clocks are pacemakers because eye removal abolishes freerunning rhythms in constant darkness (DD). If the eyes are indeed acting as pacemakers, we predicted that the two ocular pacemakers in an individual bird must remain in phase in DD and, furthermore, the two ocular pacemakers would rapidly regain coupling after being forced out of phase. These predictions were confirmed by demonstrating that 1) the ocular melatonin rhythms of the two eyes maintained phase for at least 57 days in DD and 2) after ocular pacemakers were forced out of phase by alternately patching the eyes in constant light, two components of body temperature were observed that fused into a consolidated rhythm after 5-6 days in DD, showing pacemaker recoupling. The ability to maintain phase in DD and rapidly recouple after out-of-phase entrainment demonstrates that the eyes are strongly coupled pacemakers that work in synchrony to drive circadian rhythmicity in Japanese quail.     

Circadian organization in Aplysia californica.

Substantial progress has been made in unraveling the organization of the circadian system of Aplysia californica. There are at least three circadian pacemakers in Aplysia. One has been localized in each eye and a third lies outside the eyes. Removal of the eyes disrupts the free-running locomotor activity rhythm; however, an extraocular oscillator can mediate a free-running rhythm in some eyeless animals. Although photoreceptors sufficient for entrainment of the ocular oscillator have been localized in the retina, photoreceptors outside the eyes are capable of "driving" a diurnal rhythm of locomotor activity and may also influence entrainment of ocular pacemakers. Finally, attention has been focused on the optic nerve as a coupling pathway between various parts of the system. The evidence suggests that information transmitted in the optic nerves is involved in entrainment of the ocular pacemaker by light, and in ocular control of the locomotor activity rhythm.     

Electromagnetic interference on pacemakers

External sources, either within or outside the hospital environment, may interfere with the appropriate function of pacemakers which are being implanted all around the world in current medical practice. The patient and the physician who is responsible for follow-up of the pacing systems may be confronted with some specific problems regarding the various types of electromagnetic interference (EMI). To avoid these unwanted EMI effects one must be aware of this potential problem and need to take some precautions. The effects of EMI on pacemaker function and precautions to overcome some specific problems were discussed in this review article. There are many sources of EMI interacting with pacemakers. Magnetic resonance imaging creates real problem and should be avoided in pacemaker patients. Cellular phones might be responsible for EMI when they were held on the same side with the pacemaker. Otherwise they don't cause any specific type of interaction with pacemakers. Sale security systems are not a problem if one walks through it without lingering in or near it. Patients having unipolar pacemaker systems are prone to develop EMI because of pectoral muscle artifacts during vigorous active physical exercise.     

Counter Current Line Absorption Immunoelectrophoresis is an Alternative Diagnostic Screening Test to Counter Current Immunoelectrophoresis in Aleutian Disease (AD) Eradication Programs

Counter current immunoelectrophoresis (CCIE) is the diagnostic method used in the ongoing Aleutian disease virus eradication program on Danish mink farms. There has been an increasing demand for an alternative diagnostic test especially to evaluate suspected false positive CCIE reactions. We compared test results of a number of negative and positive mink sera in indirect counter current immunoelectrophoresis (ICCIE), counter current line absorption immunoelectrophoresis (CCLAIE) and radio immuno assay (RIA) with test results from counter current immunoelectrophoresis and found that counter current line absorption immunoelectrophoresis is the best alternative diagnostic screening test to counter current immunoelectrophoresis for Aleutian disease eradication programs. Not only proved the CCLAIE test to be useful for evaluation of doubtfully positive CCIE reactions, but it was found to have a higher sensitivity than the CCIE test.     

Circadian ovulatory rhythms in Japanese quail: role of ocular and extraocular pacemakers

Previous studies have shown that the circadian system of Japanese quail is composed of multiple photic inputs and multiple oscillators. Among these are extraretinal photoreceptors that mediate both circadian and photoperiodic responses and circadian pacemakers in the eyes that, via neural and hormonal outputs, help to maintain rhythmicity of central circadian clocks (presumably located in the suprachiasmatic area of the hypothalamus). Furthermore, a component of the central circadian system is influenced by reproductive hormones. Under certain conditions, the circadian system of female quail can be induced to split into two circadian components: one driven by ocular pacemakers and one driven by feedback from reproductive hormones. Importantly, ovulation is either inhibited or permitted as these two oscillators (or sets of oscillators) constantly change internal phase relationships with each other, suggesting an "internal coincidence" mechanism in the control of ovulation. The oviposition patterns of quail in light-dark (LD) cycles also support an internal coincidence mechanism. The authors tested the hypothesis that the ocular pacemakers are an important component of an internal coincidence mechanism controlling ovulation by examinig the effects of blinding by complete eye removal (EX), and the effects of eye-patching, on the body temperature and oviposition patterns of quail exposed to 24-h LD cycles. They also examined the effects of EX on quail exposed to continuous light (LL) and to continuous darkness (DD). Neither EX nor eye-patching affected the oviposition patterns of birds in LD. Furthermore, robust body temperature and oviposition rhythms continued in EX birds in LL, but body temperature became arrhythmic in DD with the cessation of ovulation. The results do not show a role for ocular pacemakers in the control of ovulation, but they do support the hypotheses that (1) entrainment of the central oscillators by extraretinally perceived light is sufficient to preserve a normal ovulatory pattern in LD in the absence of the ocular pacemakers, and (2) in LL, feedback of reproductive hormones onto the central oscillators is sufficient to organize the circadian system even in the absence of the ocular pacemakers. Whether or not the ocular pacemakers are normally involved in the control of ovulation is still an open question.     

THE COORDINATION OF POTENTIAL PACEMAKERS IN THE HYDROID TUBULARIA

Sectioning experiments and electrical recording indicate thatthere are many potential pacemakers in polyps of the hydroidTubularia. Functionally the pacemakers are organized primarilyinto pacemaker systems, groups within which there is tight coupling.The different pacemaker systems of a polyp are loosely coupledto one another. There are two principal systems in Tubularia,one in the polyp neck (the NP system) and one in the hydranth(the HP system). In addition, there are pacemakers controllingactivities of individual tentacles. Activity in the NP systemis usually not associated with observable polyp behavior. HPsystem activity is correlated with behavioral responses termedconcerts. Concerts are probably digestive activities; they resultin the mixing of food being digested and the distribution ofthe products of this digestion. The NP systems of polyps ona colony are loosely coupled to one another through one of thethree conducting systems found in Tubularia stalks. The loosecoupling between NP systems of polyps on a colony and the loosecoupling between NP and HP systems within single polyps resultsin there being some coordination of concert activity throughouta colony.     

Organization of the Circadian System in Insects

The circadian systems of different insect groups are summarized and compared. Emphasis is placed on the anatomical identification and characterization of circadian pacemakers, as well as on their entrainment, coupling, and output pathways. Cockroaches, crickets, beetles, and flies possess bilaterally organized pacemakers in the optic lobes that appear to be located in the accessory medulla, a small neuropil between the medulla and the lobula. Neurons that are immunoreactive for the peptide pigment-dispersing hormone (PDH) arborize in the accessory medulla and appear to be important components of the optic lobe pacemakers. The neuronal architecture of the accessory medulla with associated PDH-immunoreactive neurons is best characterized in cockroaches, while the molecular machinery of rhythm generation is best understood in fruit flies. One essential component of the circadian clock is the period protein (PER), which colocalizes with PDH in about half of the fruit fly's presumptive pacemaker neurons. PER is also found in the presumptive pacemaker neurons of beetles and moths, but appears to have different functions in these insects. In moths, the pacemakers are situated in the central brain and are closely associated with neuroendocrine functions. In the other insects, neurons associated with neuroendocrine functions also appear to be closely coupled to the optic lobe pacemakers. Some crickets and flies seem to possess central brain pacemakers in addition to their optic lobe pacemakers. With respect to neuronal organization, the circadian systems of insects show striking similarities to the vertebrate circadian system. (Chronobiology International, 15(6), 567-594, 1998)     

Reuse of permanent cardiac pacemakers.

Cardiac pacemakers are part of a growing group of expensive implantable electronic devices; hospitals in which 100 pacemakers are implanted per year must budget over $300 000 for these devices. This cost represents a considerable burden to health care resources. Since the "life-span" of modern pacemakers often exceeds that of the patients who receive them, the recovery and reuse of these devices seems logical. Pacemakers can be resterilized and tested with current hospital procedures. Reuse should be acceptable under Canadian law, but the manner in which the pacemakers are recovered and the patients selected should follow careful guidelines. Every patient should provide written informed consent before receiving a recovered pacemaker. Properly executed, reuse of pacemakers should provide a high level of health care while maintaining or reducing the cost of these devices.     

Sex differences in selection of pacemakers: retrospective observational study

Objective: To evaluate the effect of patients’ sex on selection of pacemakers. Design: Retrospective univariate and multivariate analysis of a large database. Setting: German central pacemaker register. Subjects: Records collected at the register for 1992 and 1993 (n=31 913), covering 64% of all implantations in Germany. Main outcome measure: Probability of receiving a single chamber, dual chamber, or rate responsive pacemaker in relation to sex. Results: Univariate analysis showed that women were more likely to receive single chamber pacemakers and less likely to receive dual chamber or rate responsive systems than men. After demographic and clinical variables were controlled for, women were still more likely to receive a single chamber system (atrial pacing: odds ratio 0.89, 95% confidence interval 0.74 to 1.07; ventricular pacing: 0.85, 0.80 to 0.92) and less likely to receive a dual chamber (1.20, 1.12 to 1.30) or a rate responsive system (1.26, 1.17 to 1.37) than men. Conclusions: The data suggest sex differences in the selection of a pacemaker system which cannot be explained by the underlying cardiac disorder. Further research is needed to evaluate why guidelines for implanting pacemakers are not better adhered to.

Key messages

• Use of pacemakers varies despite guidelines, and the reasons for this are unclear
• In this study women were more likely to receive single chamber pacemakers and less likely to receive dual chamber and rate responsive pacemakers than men
• Demographic and clinical variables cannot fully explain these differences
• Prospective studies are needed to evaluate the effect of sex and other non-medical variables on the selection of pacemakers

     

Denaturing high-performance liquid chromatography (DHPLC) is a highly sensitive, semi-automated method for identifying mutations in the TSC1 gene

Sensitive and automated methods for the detection of DNA sequence variation are required for a wide variety of genetic studies. Diagnostic testing in human genetic disorders is one application of such methods. Tuberous sclerosis complex (TSC) is an autosomal dominant familial tumor syndrome characterized by the development of benign tumors (hamartomas) in multiple organs (OMIM # 19110, #191092). There is a high frequency of sporadic cases and significant demand from patients and families for genetic testing information. Two TSC genes have been identified (TSC1 and TSC2) and together account for all cases [1,2]. Here we report our methods for DHPLC analysis of the TSC1 gene and demonstrate the high sensitivity of this method in a blinded analysis of 21 TSC patients with known TSC1 mutations. In this series, DHPLC detected 27/28 (96%) known TSC1 sequence variations. The only sequence variation not identified by DHPLC in this study is a mosaic case.     

Use of cardiac pacemakers in Britain.

In Britain during 1975 cardiac pacemakers were implanted at the rate of 56 new patients per million population. This is about one-third the rate for other Western countries but still represents an increase of 150% since 1972. Six-thousand generators were used, and apparatus worth about 2m pounds was implanted. Over 90% of the initial implantations were by the transvenous route, and the mortality from this operation was only 0-3%. Electrode repositioning was needed in 10% of cases. The average age of patients at the time of first implantation was 70. Most patients with pacemakers were able to obtain driving licenses and insurance; only 10% had to pay an additional premium. There is no evidence from insurance comparnies that such patients have an increased risk of accidents. Patients who wished to undertake paid employment almost always did so, often in their previous job. About 80% of the patients were able to increase or maintain their leisure activities at the same level of effort as before pacing became necessary. The number of implantations may be expected to increase by about three times over the next five years.     

ZigBee无线通信技术在医疗监护领域的应用

ZigBee是部署无线传感器网络的新技术。它是一种短距离、低速率无线网络技术,是一种介于无线标记技术和BlueTooth（牙）之间的技术提案。ZigBee技术在医院监护、监狱监管以及煤矿工作等领域都逐渐开始发挥作用。     

Physiological phenomenology of neurally-mediated syncope with management implications

Background

Due to lack of efficacy in recent trials, current guidelines for the treatment of neurally-mediated (vasovagal) syncope do not promote cardiac pacemaker implantation. However, the finding of asystole during head-up tilt –induced (pre)syncope may lead to excessive cardioinhibitory syncope diagnosis and treatment with cardiac pacemakers as blood pressure is often discontinuously measured. Furthermore, physicians may be more inclined to implant cardiac pacemakers in older patients. We hypothesized that true cardioinhibitory syncope in which the decrease in heart rate precedes the fall in blood pressure is a very rare finding which might explain the lack of efficacy of pacemakers in neurally-mediated syncope.

Methods

We studied 173 consecutive patients referred for unexplained syncope (114 women, 59 men, 42±1 years, 17±2 syncopal episodes). All had experienced (pre)syncope during head-up tilt testing followed by additional lower body negative suction. We classified hemodynamic responses according to the modified Vasovagal Syncope International Study (VASIS) classification as mixed response (VASIS I), cardioinhibitory without (VASIS IIa) or with asystole (VASIS IIb), and vasodepressor (VASIS III). Then, we defined the exact temporal relationship between hypotension and bradycardia to identify patients with true cardioinhibitory syncope.

Results

Of the (pre)syncopal events during tilt testing, 63% were classified as VASIS I, 6% as VASIS IIb, 2% as VASIS IIa, and 29% as VASIS III. Cardioinhibitory responses (VASIS class II) progressively decreased from the youngest to the oldest age quartile. With more detailed temporal analysis, blood pressure reduction preceded the heart-rate decrease in all but six individuals (97%) overall and in 10 out of 11 patients with asystole (VASIS IIb).

Conclusions

Hypotension precedes bradycardia onset during head-up tilt-induced (pre)syncope in the vast majority of patients, even in those classified as cardioinhibitory syncope according to the modified VASIS classification. Furthermore, cardioinhibitory syncope becomes less frequent with increasing age.     

Model of bidirectional interaction between myocardial pacemakers based on the phase response curve

As a basis for the study of sinus rhythm determination, a model is proposed of bidirectionally-coupled oscillators as a system of difference equations based on the phase response curve of sinoatrial pacemaker cells. Solutions corresponding to the one-to-one synchronization of the two pacemakers are obtained, and the relation among those solutions is examined: It is revealed that two different solutions with different cycle length coexist, and the synchronized frequency can be higher or lower than the original intrinsic frequencies of the two pacemaker cells. The experimental results of the cultured cells of cardiac pacemakers are interpreted by the analytical result of the model.     

Utilisation of cardiac pacemakers over a 20-year period: Results from a nationwide pacemaker registry

The implantation of cardiac pacemakers has become a well-established therapy for conduction disorders and sinus node dysfunction. In many countries pacemaker registries have been initiated in order to collect information on patient characteristics, trends in numbers and the types of pacemakers used, to identify problematic devices, and for safety monitoring. For this utilisation study the Central Pacemaker Patients Registration (CPPR) from the Netherlands Pacemaker Registry Foundation (CPPR-SPRN) containing data collected for more than 20 years was used. During this period nearly 97,000 first pacemakers were implanted. Analyses show an increase in the rate of implanted devices. The change in pacemaker type from VVI to DDD, followed by biventricular stimulation, is reflected by the number of simultaneously implanted leads, which is partly a consequence of cardiac resynchronisation therapy. Our data demonstrate that indications for implantation and type of pacemaker are comparable with other European countries.