Cardiopulmonary stress test in variable frequency stimulation: a comparison of Activitrax and Nova-MR pacemakers in VVI/AAI stimulation

In seven patients with implanted intermedics NOVA MR pacemakers, we examined the cardiopulmonary effects of maximum bicycle ergometer exercise for three types of pacing in a randomized sequence: VVI or AAI at 70/min (SSI 70), rate adaptive temperature controlled with the implanted NOVA MR, and rate adaptive activity controlled by means of a Medtronic Activitrax pacemaker taped to the chest wall, which triggered the implanted Nova MR in the VVT or AAT mode via skin electrodes. The maximum exercise tolerance was 67 W with SSI 70, 71 W with Activitrax and 91 W with Nova MR. The maximum oxygen uptake was accordingly 17.6 ml/min/kg with SSI 70, 19.5 ml/min/kg with Activitrax, and 21.5 ml/min/kg with Nova MR. The highest heart rate reached was 81 beats/min with SSI 70,98 beats/min with Activitrax and 118 beats/min with Nova MR. The rate increase from rest to maximum exercise was 11 beats/min with SSI 70,29 beats/min with Activitrax and 47 beats/min with Nova MR. An increase in exercise tolerance and maximum heart rate could be achieved with both rate adaptive types of pacing, but significantly more clearly with the temperature controlled Nova MR than with the activity controlled Activitrax. However, using a different form of exercise, e.g. treadmill ergometry, the rate response of the Activitrax would presumably have been somewhat clearer.     

起搏器的休息频率功能对房性心律失常的近期影响

目的探讨起搏器的休息频率功能对房性心律失常的近期影响,评估其临床疗效和安全性。方法选择植入Identity Adx DDD 5286型双腔起搏器的病态窦房结综合征患者39例。起搏器植入后不打开休息频率,保持起搏器出厂设置;术后3个月随访时程控为在双腔起搏模式下打开休息频率,共随访6个月。比较起搏器植入前后及打开心房滞后模式后心房起搏百分比及房性心律失常的发生情况。结果与术前比较,术后3个月24 h动态心电图显示,房性期前收缩次数和房性心动过速、心房颤动阵数增加(U=4.19、4.28和4.39,均为P<0.05),相应的发作例数也增加(χ2=4.57、4.61和4.96,均为P<0.05)。与未打开休息频率模式比较,打开后心房的起搏百分比明显降低[56%(40%⁷3%)比84%(64%73%)比84%(64%⁹7%),P=0.03];24 h动态心电图显示,房性期前收缩次数和房性心动过速、心房颤动阵数明显减少(P<0.01),相应的发作例数也减少(P<0.01)。结论休息频率模式可以减少心房起搏的比例,减少房性心律失常的发生;打开休息频率模式安全可靠。     

Method for the direct comparison of the frequency behavior in QT- and activity-controlled pacemaker systems

A non-invasive method of testing the suitability of an activity-controlled pacemaker system in patients with VVT-programmable systems is presented. The QT-time controlled TX-pacemaker of a 36-year-old patient was programmed into the VVT-mode. Then the activity-controlled pacemaker (Activitrax) was fixed epicutaneously above the pectoral muscles and two stimulation electrodes were applied above the implanted pacer and the tip of the implanted probe. Thus the external could be made to trigger the implanted system. The frequency profile was recorded with identical loads with QT and/or activity control. For both the frequency-adapted pacemaker systems, the direct comparison yields characteristic frequency profiles: a quick frequency increase and decrease of both Activitrax and load, but a delayed frequency profile of the QT-controlled pacer. Different frequency maxima are rendered by the two pacemakers as a function of the load.     

具有夺获控制功能的双腔起搏器临床应用

目的　观察夺获控制功能对双腔起搏器工作电压和安全性的影响。方法　将 10例适合植入双腔起搏器的患者随机分为普通双腔组和夺获控制组 ,每组 5例 ,前者安装 Dromos DDDC普通双腔起搏器 ,后者安装 L ogos DDDC夺获控制型双腔起搏器 (均为德国 Biotronik公司产品 )。常规左锁骨下静脉穿刺植入起搏导线 ,脉冲发生器埋植在左前上胸壁。对夺获控制组除测定常规参数外 ,还在术中开启夺获控制功能并自动校正。两组患者在术后 2 4h、1周、1个月、3个月和 6个月随访 ,以动态心电图观察起搏效果 ,并对起搏器进行程控调整。结果　两组起搏器植入参数差别无显著性 ,随访期间均能安全起搏。术后 6个月夺获控制组心室常规工作电压明显低于普通起搏组。结论　 (1)与普通双腔起搏器相比 ,夺获控制型双腔起搏器的临床安全性明显增加 ,能在非预期性或临时性起搏阈值增加时提供安全起搏。(2 )夺获控制型双腔起搏器的常规工作电压明显低于普通双腔起搏器。(3)由于夺获控制过程也是耗能的过程 ,故其对双腔起搏器工作寿命的净效应有待进一步评价。 (4)与美国 Pacesetter公司的自动阈值夺获起搏器 (Microny、Regency SC / SR )相比 ,这种夺获控制功能存在如下缺点 :1不能自动测定起搏阈值和极化电位 ;2刺激脉冲电压的增加不是     

正确认识起搏器的实际起搏频率

起搏器的基本起搏频率包括下限频率、最大传感器频率和上限跟踪频率.下限频率是起搏器最基本的程控参数,出厂时常默认为60次/min.最大传感器频率指传感器驱动的最大房室频率或心室率;此外,双（三）腔起搏器具有上限跟踪频率和/或称为最大跟踪频率,指起搏器的心房通道感知P波后触发心室起搏的最大频率,在此频率以下,起搏器心室通道保持1∶1跟踪;心房率超过上限跟踪频率后,起搏器转换为非1∶1跟踪,避免在房性快速心律失常时发生较快的心室起搏.     

Cardiopulmonary function after segmental resection of the lung

By the combination of radiocardiography, ergooxytensiometry and heart probing on 22 lobectomized, cone- and segment-resected patients, respectively could be established in comparison to control groups that also after parenchyma-saving lung resection a pulmonary load parenchyma-saving lung resection a pulmonary load hypertension develops in 15 patients. The sequel of this increase of pressure and resistance in the pulmonary circulation is a functional insufficiency of the heart in 11 cases which is to objectify by reduction of the stroke volume, increase of the end-diastolic and end-systolic volume and by reduction of the contractility of the myocardium.     

儿童置入频率适应性起搏器前后药物负荷左室收缩功能的研究

目的　了解儿童完全性房室传导阻滞（ＣＡＶＢ）置入频率适应性起搏器前后左室收缩功能的变化。方法　对６ 例３～１２ 岁ＣＡＶＢ患儿,采用多巴酚丁胺负荷超声心动图技术测定起搏器置入术前及术后３～６ 月的左室短轴缩短率（ＦＳ）、射血分数（ＥＦ）、室壁增厚率（ＬＶＰＷＴ）、应变率（ＭＶＣＦＣ） 、每搏指数（ＳＩ） 及心排指数（ＣＩ）,并与８ 例正常同龄儿童进行对比分析。结果　术前ＦＳ及ＥＦ均随药物浓度增加而稍增大,但与对照组比较无显著差异,Ｐ 均＞ ０－０５;ＬＶＰＷＴ、ＭＶＣＦＣ及ＳＩ于静息状态及低药物浓度时明显高于对照组,Ｐ＜０－０５,随药物浓度增加而无明显增大,Ｐ＞ ０－０５;ＣＩ于静息状态及低药物浓度时与对照组无差异,Ｐ＞０－０５,但随药物浓度增加而出现明显差异,Ｐ＜ ０－０５。术后ＬＶＰＷＴ、ＭＶＣＦＣ、ＳＩ、ＣＩ均随药物浓度增加而增大,与对照组比较无明显差异,Ｐ＞０－０５ 。结论　ＣＡＶＢ 患儿,静息状态下左室收缩功能正常,但药物负荷状态下出现储备功能不足,置入频率适应性起搏器后左室收缩储备功能可达正常。     

Termination of sustained ventricular tachycardia with a new antitachycardia pacemaker: role of the nonautomatic mode to follow pacemaker function

The use of an antitachycardia pacemaker for the treatment of recurrent, drug resistant nonsyncopal sustained ventricular tachycardia in a 28-year-old patient is described. The report emphasizes the role of electrocardiographic recording during manual activation of the tachycardia response in an outpatient setting. The follow-up covers 12 months with 26 spontaneous tachycardia episodes forcing the patient to go to an emergency room to monitor tachycardia termination. Mean ventricular tachycardia cycle length was 340 +/- 21 ms. Tachycardias were terminated either by the primary or secondary modality without acceleration or degeneration to ventricular fibrillation. Thus, it was possible to assess the efficacy and the safety of the termination programs. Unlike during intensive in-hospital testing, restoration of stable sinus rhythm was complicated by re-emergence of ventricular tachycardia. It is concluded that manual activation with medical supervision provides safe management of selected patients with ventricular tachycardia. However, in-hospital testing overestimated, in this case, the efficacy of tachycardia response modalities to terminate spontaneous tachycardia episodes. The customization of an antitachycardia pacemaker with an automatic implantable cardioverter/defibrillator may increase the quality of life as it would allow switching to automatic pace termination.     

Ten-year experience of 359 epicardial pacemaker systems: complications and results

In the last ten years (1970-1980) 457 patients underwent permanent pacemaker insertion in the Brompton Hospital. Our practice has been somewhat atypical in that the majority of these patients had epicardial leads, initially using a Cordis intramural sutured electrode (85 patients), and subsequently a Medtronic sutureless electrode (274 patients). Our initial experience with these electrodes was satisfactory, but more recently it has become apparent that the long-term morbidity and complication rate is high. The respective complication rates being 25% and 18% for sutured and sutureless epicardial electrodes. In this study, lead complications were defined as those requiring lead replacement, and problems most commonly encountered were high voltage threshold, infection, and lead fracture. Unless there are specific indications for epicardial pacing it is now our policy to treat patients requiring permanent pacing with endocardial systems. Our complication rate with this technique (90 patients) is significantly lower (9%).     

Generation and control of cardiac pacing the pacemaker current

Several currents contribute to the electrical activity of mammalian pacemaker cells. Of these, the hyperpolarization-activated current, i(f), is involved in the generation of the diastolic depolarization phase, and therefore has a main role in controlling the most peculiar feature of these cells: their ability to beat spontaneously and to drive the heartbeat. More than this, i(f) represents the key mechanism by which sympathetic and parasympathetic stimuli regulate, via the diastolic depolarization phase, the pacing frequency of sinoatrial node cells and thus the heart rate. This is achieved through regulation of adenylyl-cyclase activity and of intracellular cAMP, which is the second messenger in i(f) modulation. A fine regulation of i(f) is thus the basis by which epinephrine and acetylcholine exert their fine control on cardiac rhythm.     

The effect of chronic variable stress on bowel habit and adrenal function in rats

Background and Aim: Increased colonic motility is a well‐known stress response and corticotropin releasing hormone plays an important role in this response, but sequential change of bowel habit and adrenal function during chronic stress has not been reported. The objective of this study was to evaluate the effect of chronic stress on bowel habit and adrenal function. Methods: Male Sprague‐Dawley rats were exposed to chronic variable stress (CVS) for 6 weeks. We measured daily the number and weight of pellets and weekly urinary corticosterone. After 6 weeks of experiment, visceromotor response (VMR) to colorectal distention (CRD), serum corticosterone and adrenal glands weight were measured. Results: The number and weight of pellets in CVS rats was greater than those of the control rats initially and decreased during the later period. However, CVS rats showed continuously exaggerated daily variation of pellet number than control rats to the end of experimental period. Urinary corticosterone was increased in CVS rat until the fifth week, but urine and serum corticosterone were not statistically different between groups at the sixth week. However, the relative weight of adrenal glands was higher in CVS rats at the sixth week. CVS rats showed exaggerated VMR to CRD than the control rats. Conclusions: The prolonged and variable stress to rats induced sustained bowel habit dysfunction and visceral hypersensitivity without adaptation. Chronic stress also increased adrenal activity from the early phase and finally caused adrenal hypertrophy with relatively decreased activity. But adrenal change was not parallel to bowel habit change and it remains to be seen whether adrenal dysfunction is directly related to bowel habit dysfunction.     

Critical comparison of uni- and bipolar pacemaker systems

More than 90% of all implanted pacemaker systems in Germany up to the present were unipolar. Stimulation and sensing therein, take place between the cathodal electrode tip and the anodal pacemaker. A relatively large chance of noise interference is allowed by the large distance between the two poles. The high sensitivity, at is needed for correct function, enables intra- and extracorporal noise signals to interfere. This disadvantage of unipolar systems is mainly avoided when using bipolar systems. Since both poles are situated close to each other within the heart, there is only a very small chance of notice interference. However, there are many arguments in favour of both systems. In recent years there has been a slight trend towards bipolar pacing. By reducing the well-known disadvantages of bipolar pacing, such as increased conductor resistivity, as inferior energy function, greater coil diameter and reduced handling, the beneficial effects of bipolar pacing--mostly the clear discrimination between physiological cardiac and extraneous signals--become more important. A new 3.2 mm universal connector (VS-1) might help to realize bipolar pacing more easily. In the future, a pacemaker system with unipolar pacing and simultaneously a bipolar sensing function, might help to increase safety in pacing.     

Cardiopulmonary stress testing. A review of noninvasive approaches

With readily available techniques, cardiopulmonary exercise testing permits noninvasive measurement of such parameters as heart rate, cardiac output, oxygen saturation, ventilation, and gas exchange to bring out abnormalities which are either underestimated or not detectable at rest. These parameters may be used to characterize a patient's primary limitation of exercise tolerance as either cardiac or pulmonary in origin. They can also provide precise data to assess response to treatment. Pulmonary gas exchange is evaluated primarily by measurement of oxygen consumption, carbon dioxide production, and ventilation over time. The relationship of these parameters to one another changes throughout the course of incremental exercise testing. By appreciating these basic relationships, the more complex abnormalities found in disease states can be understood.