Effect of different body-exercise modes on the rate response of the temperature-controlled pacemaker Nova MR

In order to evaluate the effect of different modes of physical exercise on the rate response of the temperature-controlled Nova MR, parameters such as temperature behaviour and correlation of work load to pacing rate were investigated using different types and protocols of stress testing. This study considered 21 patients (age: 66 +/- 12 y). The indications for the Nova MR were AV block (n: 14) and sick sinus syndrome (n: 7). The patients performed two different types of exercise (treadmill n: 13, bicycle n: 14) based on different protocols. We registered the surface ECG, pacing rate, exercise time, and (via data transmission by the RX 2000 programmer) blood temperature and pacing rate. An adequate rate response could be achieved with all the different types of exercise and protocols using more sensitive program settings. The type of stress testing used to adjust or evaluate the Nova MR seems to be secondary, although cycling as compared with treadmill exercise resulted in a slightly weakened reaction of temperature and pacing rate. Our investigations revealed a good correlation between work load and pacing rate independent of the type of stress testing. The initial DIP (48%) is not a constant phenomenon and showed inter- and intraindividual variations. Impressive psychological influences also exhibited an effect on temperature and pacing rate, sometimes preventing a DIP response. During exercise at lower work loads (under 50 watts, shorter than 3-4 min) the rate response of the Nova MR--without any detected DIP--is often delayed due either to a decrease or to a late and flat increase in temperature. An additional fast-reacting sensor could be advantageous in triggering the initial rate response in such cases.     

房室间期自动搜索功能对心室起搏及心功能的影响

目的 观察自动AV间期搜索功能双腔起搏器减少心室起搏和高频心房事件的效果及对心功能的影响.方法 60例置入DDD/R起搏器的患者（有AV搜索功能30例,无AV搜索功能30例）,术后1年内程控获取右室起搏百分比、高频心房事件,检查超声心动图,测试血浆利钠肽（BNP）值.结果 有AV搜索功能组术后6个月和12个月右室起搏百分比明显小于无AV搜索功能组[（21.2±6.0）％比（78.3±7.5）％,（19.1±6.5）％比（73.4±7.9）％,P均＜0.05）.AV搜索功能组左室射血分数、左室Tei指数均明显改善（0.57±0.03比0.53±0.05,0.48±0.15比0.68±0.20,P均＜0.05）;BNP水平明显降低[（75.2±34.5）pg/ml）比（37.0±16.4）pg/ml,P＜0.05];高频心房事件也显著减少[（42±10）次比（19±11）次,P＜0.05].结论 AV自动搜索功能起搏器可有效减少不必要的右室起搏及高频心房事件,改善血流动力学效应.     

The Activitrax rate responsive pacemaker system

Bipolar Medtronic Activitrax rate responsive pacemakers were implanted in 31 patients for ventricular (28) or atrial (3) pacing. Mean follow-up was 16 months (range 10 to 26). Twenty pacemakers were implanted after catheter ablation of the His bundle, 7 for sick sinus syndrome. 1 for atrioventricular block and 3 for sick sinus syndrome with atrioventricular block. A rate response value was selected that gave a pacing rate of about 100 pulses/min during walking. Of the 31 patients, all had 24-hour ambulatory electrocardiographic monitoring with diary, 11 walked a 20-minute circuit, including a flight of stairs, and 20 had a treadmill exercise test. In 9 patients the pacing rate could be compared with the underlying sinus rate during exercise and was seen to match it very closely. In 12 patients the pacing rate during car driving was found to be similar to the sinus rate of 5 volunteers under similar conditions (mean minimum and maximum rate was 80 and 99 pulses/min, respectively). No pacing-induced arrhythmias were seen during ambulatory electrocardiographic monitoring. At high pacing rates slightly irregular pacing intervals were sometimes observed, which was due to polarization sensing. Sporadically, 1 pacing interval shortened to the upper rate value, because of a known and now resolved timing anomaly. Neither anomaly was of clinical consequence and the first could be resolved by reprogramming.(ABSTRACT TRUNCATED AT 250 WORDS)     

Age-related changes in the rate of muscle activation and rapid force characteristics

GeroScience - Declines in muscle size and strength are commonly reported as a consequence of aging; however, few studies have investigated the influence of aging on the rate of muscle activation...     

The effect of heart rate on the working capacity of patients with complete heart block and physiological pacemaker.

The effect of heart rate (HR) on maximum working capacity was studied in 18 patients (mean age 55 years) with a physiological pacemaker implanted for chronic complete heart block of different aetiology. Exercise testing was performed by bicycle ergometry in 3 pacing protocols in randomized sequence, and without the patients knowing the preprogrammed pacing mode: 1) VVI pacing at a rate of 30 beats/min--exercise on heart block; 2) VVI pacing at a rate of 70 beats/min; 3) physiological DDD or QT pacing. While patients with heart block had a mean HR of 54 +/- 16 beats/min and working capacity of 81 +/- 31 W, on VVI 70 pacing the values were 73 +/- 9 beats/min (+35%, p < 0.002) and 100 +/- 45 W (+24%, p < 0.008), respectively. Exercise during physiological pacing led to an increase in HR to 140 +/- 15 beats/min (+169%, p < 0.002) and in working capacity to 130 +/- 52 W (+61%, p < 0.002). Thus, the increment in working capacity was 2.5 times higher on physiological than standard ventricular pacing (p < 0.005) if compared with the working capacity of patients with heart block.     

The effect of lidocaine on diastolic transmembrane currents determining pacemaker depolarization in cardiac Purkinje fibers.

We studied the effects of lidocaine (1-5 mg/liter) on the diastolic currents of sheep Purkinje fibers by the two-microelectrode voltage clamp technique to obtain additional information on how lidocaine decreases the slope of spontaneous diastolic depolarization of mammalian Purkinje fibers. During voltage clamps we measured both the magnitude and time course of activation and deactivation of the time- and voltage-dependent potassium "pacemaker current" (iK2), and also the steady state current-voltage relationship throughout the pacemaker voltage range. At a concentration of 1 mg/liter lidocaine had no effect on the amplitude of iK2. In contrast, at 5 mg/liter, lidocaine diminished the magnitude of iK2 throughout the voltage range of pacemaker depolarization. Lidocaine (1-5 mg/liter) had no effect on either (1) the transmembrane voltage at which iK2 is half-activated, (2) the reversal voltage for iK2, or (3) the kinetics of iK2. Lidocaine (1-5 mg/liter) increased the steady state outward transmembrane current. This effect of lidocaine can be attributed to a variable contribution from both an increase in time-independent outward potassium current (iK1) and a decrease in background inward current.     

Historical development of the cardiac pacemaker

The history of electric cardiac stimulation is long and fascinating. It is not only the anatomy of the heart, but also the analysis of the peripheral pulse that plays an important role in the history of cardiac pacing. The Romans, the Greeks and even before them the Chinese attempted to explain the origin and variations of the pulse as the basis of further investigations. - The growing clinical importance has been recognized and renewed as Zoll in 1952 described a successful resuscitation in cardiac standstill by external stimulation. Meanwhile more than 3 million patients with disorders of cardiac rhythm have been treated all over the world in the last 25 years. Recently the technical refinements of intracardiac stimulation and defibrillation improved our knowledge of cardiac physiology and diseases, and arrhythmias in particular. The pertinent interest in these dramatic developments and the intention to learn more about the basic fundamentals are reasons to look at the history of cardiac pacing. The advances in the field of therapeutic and diagnostic application of cardiac pacing will continue as rapidly as before in order to give us further significant aid in taking care of the patient.     

冠心灵对冠脉血流量、心肌收缩力和心电活动的影响

目的 :研究中药复方制剂冠心灵的心血管作用并初步探讨其作用机制。方法 :运用细胞内微电极技术、L angendorff离体心脏灌流和心率变异性功率谱分析等方法 ,研究冠心灵对心肌细胞动作电位的影响 ;观察其对冠脉血流量和心肌收缩力的作用 ;分析冠心灵对冠心病患者心率变异性的影响。结果 :冠心灵增强 Ca2 +跨膜内流 ;增加冠脉血流量和心肌收缩力 ;改善因缺血导致冠脉流量和心肌收缩力的下降 ;功率谱分析显示心迷走交感对心率的调控作用比升高。结论 :冠心灵有改善心肌缺血的作用。     

频率适应性起搏器对老年病态窦房结综合征患者生活质量的影响

目的 观察老年病态窦房结综合征患者，植入频率适应性起搏器后生活质量、心脏功能及运动耐量等改变，以探讨频率适应性起搏器对老年患者生活质量的影响。方法 经临床、食管心房调搏、动态心电图和运动试验心电图确诊病态窦房结综合征且合并窦房结变时功能不良的30例老年患者，择期植入永久双腔频率适应性起搏器（DDDR），于起搏器植入术后即刻及12个月后将起搏器分别程控为非频率适应性起搏模式（DDD）和频率适应性起搏模式（DDDR）。两种模式下起搏器各工作12个月，定期随访，采用SF-36生活质量调查表，进行问卷调查；动态心电图监测24h日常活动时心率变化；症状限制性活动平板运动试验观察运动持续时间，最大起搏频率；超声心动图测定最大运动负荷时每搏量、每分心排出量。结果 本组患者DDDR模式下SF-36调查表的总得分118．60±7．12比DDD模式下该表总得分95．27±7．56提高了24％，P〈0．001，生活质量较DDD模式有显著提高；运动持续时间和最大心排出量均较DDD模式明显增加[（386．20±67．72）s vs（274．10±56．88）s，P〈0．001；（9．97±1．03）／min vs（6．30±0．79）／min，P〈0．001]。结论 频率适应性起搏器可明显改善老年病态窦房结综合征患者的生活质量和运动耐量。     

Cardiac muscle fiber force versus length determined by a cardiac muscle crossbridge model

Summary A mathematical model incorporating Huxley's sliding filament crossbridge muscle model coupled with parallel and series elastic components was simulated to examine force-length relations under different external calcium concentrations. Several researchers have determined experimentally in both papillary muscle preparations and in situ heart experiments that the calcium concentration (or effective concentration from inotropic agents) will affect the strength and convexity of the cardiac muscle fiber force-length relations. Simulations were performed over a several-order-of-magnitude range of calcium concentrations in isometric contractions and these showed that the force-length curve convexity was changed. Simulation results demonstrated that increasing the stiffness in the model contractile element or series elasticity element did not change the force-length convexity. Increasing the series elasticity element stiffness did slightly change the shape of the force-length curve. The model predicts that the curve convexity changes as a result of the calcium-troponin interactions.On leave from the Yale School of Medicine 367 Cedar St., New Haven, CT 06510 USA     

不同心脏起搏器植入术后对患者生活质量影响的比较

【摘要】：目的 采用起搏器生活质量测定量表评价不同心脏起搏器植入术后对患者生活质量的影响。方法 随机选择2010年1月至2013年7月在新疆自治区人民医院心内科因缓慢型心律失常收治住院并植入心脏起搏器的患者156例, 根据起搏方式分为VVI 起搏组、AAI起搏组、DDD起搏组;按照起搏器生活质量测定量表计分规则,分别于植入术前、术后3个月、术后1年进行随访并计算生活质量得分,分值越低说明生活质量状况越好。结果 （1）与起搏器植入前比较,患者术后3个月、1年的生活质量在躯体功能、心理功能、社会功能及一般认知功能4个方面分值均有所下降,患者的临床症状得到不同程度的缓解,差异具有统计学意义(P<0.05);（2）各组间不同时期两两比较显示3种起搏方式对患者心理功能、社会功能、一般认知功能3个方面改善无差异（P>0.05）,在躯体功能改善方面,AAI起搏组与DDD起搏组之间无差异（P>0.05）,VVI 起搏组与AAI起搏组之间有显著差异（P=0.029）,VVI 起搏组与DDD起搏组之间有显著差异（P=0.033）。结论 心脏起搏器植入后能显著提高患者术后的生活质量, AAI起搏组和DDD起搏组在改善患者改善躯体功能方面显著优于VVI 起搏组,提示接受生理性起搏器植入的患者术后生活质量高于非生理性起搏患者。     

The rate-limiting step in muscle contraction

Summary The motion of skinned muscle fibers in chemically controlled bathing solutions is examined to obtain information about the cross bridge cycle. The effects of an ATP regenerating system and ionic strength on both the transient and the steady response to step changes in load are compared. The transient is changed in characteristic ways by these factors, but the steady motion is unaffected. If changes in the transient reflect changes in the rates of making and breaking cross bridges, these results suggest that the rate of physiological contraction is limited by a slow transition in the unattached myosin molecule rather than the making and breaking of cross bridgesper se.

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Der geschwindigkeitsbegrenzende Schritt bei der Muskelkontraktion

Zusammenfassung In Badelösungen bekannter Zusammensetzung wurde die Verkürzung gehäuteter Muskelfasern untersucht, mit dem Ziel, Informationen über den Querbrückenzyklus zu erhalten. Die Effekte eines ATP-regenerierenden Systems und der Ionenstärke auf die transitorische Phase nach stufenweiser Änderung der Last und auf die Verkürzungsgeschwindigkeit nach Erreichen eines Gleichgewichtszustandes werden verglichen. Die Übergangsphase wird durch diese Faktoren in charakteristischer Weise verändert, während der anschließende Verkürzungsprozeß unbeeinflußt bleibt. Sofern Änderungen in der transitorischen Phase Veränderungen in der Geschwindigkeit der Bildung und Ablösung der Querbrücken widerspiegeln, lassen diese Ergebnisse vermuten, daß die Geschwindigkeit der physiologischen Kontraktion durch eine langsame Veränderung am Myosinmolekül im nicht angehefteten Zustand begrenzt wird und nicht durch die Bildung und das Ablösen der Querbrücken per se.

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Paper, presented at the Erwin Riesch Symposium, Tübingen, April 3–7, 1979

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With 3 figures     

Adrenaline increases the rate of cross-bridge cycling in rat cardiac muscle

To characterize the myocardial cross-bridge dynamics in catecholamine-induced positive inotropic state, we studied the effects of adrenaline (6 X 10(-6) M) on the transient central segment length (SL) response to step decrease in tension in rat right ventricular papillary muscle in barium contracture. The time course of this response is thought to reflect the kinetics of actin-myosin interaction. The muscle was released stepwise from the steady contracture tension (Tc) to new steady tension levels (Tr) of varying magnitudes at 22 degrees C. When the tension decrease was less than 0.7 Tc, the SL transient responses comprised, in most cases, four phases. The first phase was a rapid and minute shortening during tension reduction; the second was a slow further shortening; the third, a slow lengthening; and the fourth, an extremely slow shortening toward a new steady length under the new tension. Adrenaline showed almost no effect on Tc and the amplitude of SL transients, but markedly reduced the duration of the second (D2) and third (D3) phases of SL transient regardless of the amplitude of tension reduction. The reduction of duration was 14 +/- 3% in D2 and 26 +/- 5% in D3 at Tr/Tc of 0.84 +/- 0.03 on the average (mean +/- S.D.) in nine preparations. The velocity measured from the quasi-steady SL shortening in the second phase increased with the addition of adrenaline, regardless of the amplitude of tension reduction. The increase in the shortening velocity was 16 +/- 6% (mean +/- S.D., n = 9) at Tr/Tc of 0.18 +/- 0.04. These results suggest that adrenaline increases the rate of cross-bridge cycling in cardiac muscle independent of activation level.     

Proportionality of rate response to metabolic workload provided by a rate adaptive pacemaker with automatic rate profile optimization.

OBJECTIVE: The rate response of a pacemaker (PM) was compared with the sinus rate in patients during repeated exercise tests, at different settings of the rate response parameters. METHODS AND RESULTS: In patients with paroxysmal sick sinus syndrome (n=3) or atrioventricular block (n=8), a rate responsive PM was implanted. The activity-dependent pacing rate is represented by the sensor indicated rate (SIR). Each patient performed a treadmill test at 1 month, 1 year, and 2 years after implantation. Prior to the 1 and 2 year tests PM parameters were changed to produce a larger rate increase, especially at moderate levels of daily life activity. During the tests the O(2) consumption and CO(2) production were measured, breath-by-breath, to determine the workload and the anaerobic threshold. On average the workload (oxygen consumption), the patient's sinus rate, and the SIR, showed a linear increase with the workload imposed by the treadmill. In the 1 month and 1 year test the SIR was much lower than the spontaneous rhythm, especially at low or moderate workloads. On the more dynamic setting of several rate adaptive parameters at 2 years, the SIR changed significantly and was close to the spontaneous HR. CONCLUSIONS: The examined PM provides a paced heart rate that is proportional to the workload. For the first time the effect of reprogramming rate response parameters to produce an SIR that is similar to the sinus rate is shown in this study.