A microcomputer-based system to evaluate cardiac pacing for the treatment of tachycardias

A microcomputer-based pacemaker system for the evaluation of pacemaker treatment of tachycardia is described. The system may be used to study tachycardia initiation, tachycardia termination or a combination of the two. The software incorporates a visual display unit screen handling package which provides the user-system interface. System-patient interfacing is performed by a separate pacing and sensing unit which communicates with the computer via standard digital input/output lines. Several pacing options are available, selectable from a screen-displayed menu. Each selection also has an associated set of programmable parameters which may be adjusted, within allowed limits, to suit particular studies. Examples of the use of the system for tachycardia termination are given. The main programming language for the controlling software was Fortran IV. Some routines were necessarily written in assembly language. The system is useful for evaluation purposes and forms the basis of a cardiac pacemaker development tool.     

Polarisation impendance of pacemaker electrodes:in vitro studies simulating practical operation

The electrical properties of pacemaker electrodes were studiedin vitro under conditions prevailing in practical pacemaker operation. Emphasis was laid on a clear distinction between the changing modes of the pacemaker action. During sensing, the electrode can be represented by an a.c. series polarisation resistance and capacitance, generally accepted for biological electrodes obeying linearity rules. During stimulation, the electrode operates in the non-linear region. A nearly constant-voltage, short, rectangular pulse applied directly to the electrode-heart system, causes the electrode voltage and current to respond as a transient exponential, characterised approximately by a single time constant. This response allows modelling of the d.c. equivalent circuit of the electrode, in the form of a polarisation capacitance with a small resistance in series, shunted by a parallel resistance. Formulae were derived for calculation of these elements. The response of the electrode-heart system to a single stimulus was tested as a function of the amplitude and duration of the applied pulse. Also, the effect of repetitive stimulations was checked at a normal pacing rate. A nearly constant-voltage pacing source, as compared with a constant-current one, appears to be advantageous for preservation of the longevity of the electrode.     

超声引导下临时心脏起搏电极心内定位的临床应用

目的：探讨应用超声引导临时心脏起搏电极心内定位的可行性和这一新方法的实用价值。方法：经皮穿刺右侧颈内静脉或右侧锁骨下静脉,在超声引导下将起搏电极送至右室心尖部进行临时起搏。结果：21例患者均能顺利地将电极定位在右室心尖部并能成功起搏。结论：应用超声替代X光行临时心脏起搏器安装术具有实用价值,值得临床推广应用。     

Current benzodiazepine issues

This article deals with some of the recent evidence bearing on the issues of the liability of benzodiazepines to lead to abuse, dependence, and adverse behavioral effects. Reviews of epidemiological, clinical and experimental literature indicated that the previous conclusion about abuse of these drugs still holds: the vast majority of the use of benzodiazepines is appropriate. Problems of nonmedical use arise nearly exclusively among people who abuse other drugs. Nevertheless, there are reasons for concern about patients who take benzodiazepines regularly for long periods of time. These drugs can produce physiological dependence when taken chronicaly, and although this does not appear to result in dose escalation or other evidence of psychological dependence, physiological dependence can result in patient discomfort if drug use is abruptly discontiniued. Also, physicians are currently prescribing shorter-acting benzodiazepines in preference to longer-acting benzodiazepines. The shorter-acting drugs can produce a more intense withdrawal syndrome following chronic administration. Furthermore, rates of use of benzodiazepines increase with age, and elderly patients are more likely than younger ones to take the drug chronically. The clearest adverse effect of benzodiazepines is impairment of memory. This, too, may be particular concern in older patients whose recall in the absence of drug is typically impaired relative to younger individuals, and who are more compromised following drug administration.This article was supported by USPHS Grant DA-00254 and by funding from Hoffmann-La Roche, Inc.     

心脏介入治疗院内感染的调查分析

目的：对我科心脏介入治疗后的院内感染发生率及易感因素进行回顾性调查分析,并探讨其防治措施。　方法： 我科自１９７３～１９９９年６ 月共收治行心脏介入治疗患者１ １００ 例,按照年龄、性别、手术种类、院内感染发生率及感染部位等资料进行比较分析。　结果：１ １００ 例患者中,术后感染２７例,感染率为２．４５％ 。包括经皮二尖瓣球囊成形术（ＰＢＭＶ）３８０ 例,感染２１ 例,感染率为５．５３％ ;永久性心脏起搏器安置术５２０ 例,感染６ 例,感染率为１．１５％ ;射频消融术２００ 例,无感染发生。最常见的感染为血管相关性感染和切口感染。感染发生与性别无显著相关性。　结论： 心脏介入治疗后院内感染发生率较低,通过严格的无菌操作和抗生素的合理应用,可防止院内感染的发生。     

心房按需起搏时心内电图的形态与起搏参数的关系

目的： 观察心房按需起搏（ＡＡＩ）时心内电图的形态与起搏阈值等参数的关系。　方法：对３６ 例ＡＡＩ起搏时记录的心内电图的Ａ 波形态、振幅、Ａ－Ｖ段上抬幅度进行详细测定,并与起搏阈值、心肌阻抗等参数进行相关分析。　结果：Ａ波形态、振幅与起搏阈值、心肌阻抗均无显著相关（Ｐ＞ ０．０５）,而Ａ－Ｖ 段上抬的幅度与起搏阈值呈明显负相关（ｒ＝ － ０．５４８ ６, Ｐ＜ ０．０５）。Ａ－Ｖ段高抬组的起搏阈值（０．６８±０．１７）Ｖ,显著低于Ａ－Ｖ段低抬组的（１．１±０．２４）Ｖ （Ｐ＜ ０．０１）。　结论：心内电图Ａ－Ｖ段上抬的足够幅度（＞ ０．３ ｍ Ｖ）可作为ＡＡＩ起搏时的一个重要技术指标,对避免电极脱位、保证较低的起搏阈值水平均具重要的临床意义。     

单电极VDD心脏起搏治疗肥厚性梗阻型心肌病(附1例报告)

目的：用ＶＤＤ心脏起搏治疗１ 例肥厚性梗阻型心肌病（ＨＯＣＭ）,并观察其临床及血流动力学效果。　方法：常规方法植入ＶＤＤ型心脏起搏系统,设置房室起搏间期１２０ ｍ ｓ,心房感知０．１５ ｍ Ｖ,起搏前后进行左室流出道压力阶差等血液动力学对比观察。　结果：术后房室同步起搏率为１００％ ,左室流出道压力阶差从６．８ ｋＰａ（５１．４ｍ ｍ Ｈｇ）降至２．８１３ ｋＰａ（２１．１ ｍ ｍ Ｈｇ）,二尖瓣前移现象消失,临床症状明显改善,随访期间未再出现晕厥。　结论：ＶＤＤ起搏植入简便、房室同步功能稳定,对ＨＯＣＭ 患者不失为一种新的有效的治疗方法。     

食道心房调搏心负荷试验诊断冠心病的价值

目的探讨食道心房调搏心负荷试验（ＴＥＡＰ）诊断冠心病的价值,并与活动平板运动试验（ＴＭＥＴ）进行对比,同时对冠状动脉病变程度进行评估。方法自１９９３年５月～１９９７年１０月,８０例拟诊冠心病的住院病人同期行ＴＥＡＰ、ＴＭＥＴ及ＣＡＧ检查;以ＣＡＧ为诊断标准,确诊为ＣＨＤ者６０例,另２０例为ＣＡＧ正常者。ＣＡＧ均为右股动脉Ｓｅｌｄｉｎｇｅｒ法穿刺,ＪｕｄｋｉｎＳ法进行。ＴＥＡＰ、ＴＭＥＴ以心率达到次极限水平,二阶梯运动试验方法记录ＥＣＧ。结果ＴＥＡＰ诊断ＣＨＤ的敏感性、特异性为８１．６７％、９０％,并且与ＣＨＤ患者冠状动脉病变支数呈正相关。其与ＴＭＥＴ的敏感性、特异性相比更可靠（Ｐ＜０．０１）。结论食道心房调搏心负荷试验可以作为一种无创伤性、有效、简便的诊断ＣＨＤ的方法。并可对冠状动脉病变程度进行初略评估。